Placeholder Image

字幕列表 影片播放

  • >> HELLO.

  • WELCOME TO TODAY'S WEDNESDAY AFTERNOON

  • LECTURE AT NATIONAL INSTITUTES

  • OF HEALTH.

  • THANK YOU FOR COMING.

  • MY NAME IS JUSTIN TERASKA.

  • I'M AN INVESTIGATOR IN THE

  • LABORATORY OF MOLECULAR

  • BIOPHYSICS IN THE NATIONAL HEART

  • LUNG AND BLOOD INSTITUTE.

  • IT'S MY PLEASURE TO INTRODUCE

  • DR. JAMES ROTHMAN AS TODAY'S

  • WALS SPEAKER.

  • DR. ROTHMAN IS WALS PROFESSOR OF

  • BIOMEDICAL SCIENCES AND CHAIR OF

  • DEPARTMENT OF BIOMEDICAL AT

  • YALE.

  • HE'S ONE OF THE MOST INNOVATIVE

  • AND INFLUENTIAL CELL BIOLOGISTS

  • AND BUY CHEMISTS WORKING OFFER

  • THE LAST FEW DECADES.

  • DURING TENURES AT STANFORD,

  • PRINCETON, INVENTORY DEBT R,

  • COLUMBIA AN YALE, -- CLONE

  • KETTERING AND YALE, THIS IS

  • INCLUDED SEMINOLE DISCOVERIES

  • RELATED TO HOW PROTEINS INSERT

  • INTO MEMBRANES.

  • HOW VESICALES TRAFFIC THROUGH

  • THE CELL, AND HOW VESICALES FUSE

  • WITH THE MEMBRANE, A PROCESS

  • CALLED EXOCYTOSIS.

  • ASIDE FROM THE BIOLOGICAL

  • DISCOVERIES HIS LAB HAS INVENTED

  • IMPORTANT METHODS INCLUDING IN

  • VITRO RECONSTITUTION OF VESICAL

  • TRAFFICKING PATHWAYS WHICH HAS

  • REALLY ALLOWED THE COMPLEX STEPS

  • OF VESICAL TRAFFICKING TO BE

  • TEASED APART AT THEIR MOST

  • FUNDAMENTAL LEVEL H.

  • ADDITIONALLY DEVELOPED NOVEL PH

  • FLUORESCENCE PROTEINS THAT ALLOW

  • INDIVIDUAL SYNAPSES AND SINGLE

  • VESICALES TO BE WATCHED IN

  • LIVING CELLS IN REAL TIME.

  • IN PARTICULAR, DR. ROTHMAN HAS

  • HELPED TO ESTABLISH THE SNARE

  • HYPOTHESIS OF MEMBRANE FUSION

  • WHICH PROPOSES THAT THE CORRECT

  • PAIRING OF ALPHA HELICAL

  • PROTEINS ON TWO OPPOSED

  • MEMBRANES DIRECTS AND CATALYZES

  • THEIR FUSION.

  • ALONG WITH THESE IMPORTANT

  • DISCOVERIES DR. ROTHMAN MENTORED

  • AND TRAINED MANY PROMINENT

  • SUCCESSFUL BIOCHEMISTS AND CELL

  • BIOLOGISTS.

  • HE'S A MEMBER OF THE NAB

  • NATIONAL ACADEMY, INSTITUTE OF

  • MEDICINE AND RECIPIENT OF

  • NUMEROUS AWARDS INCLUDING LASTER

  • AWARD FOR BASIC SCIENCE AND

  • CAVALI PRIZE FOR NEUROSCIENCE.

  • HE WILL DISCUSS HIS RECENT WORK

  • ON SNARES AND THE ACCESSORY

  • PROTEINS THAT DIRECT THEIR

  • FUSION.

  • IN A TALK TITLED MOLECULAR

  • MECHANISMS OF SYNCHRONOUS

  • NEUROTRANSMITTER RELEASE. AFTER

  • THE SEMINAR THERE WILL BE A

  • RECEPTION IN THE LIBRARY SO

  • PLEASE COME AND THEY'LL GIVE YOU

  • AN OPPORTUNITY TO SPEAK MORE

  • INFORMALLY WITH DR. ROTHMAN.

  • JOIN ME GIVING A WARM WELCOME TO

  • JIM ROTHMAN.

  • [APPLAUSE]

  • >> THANK YOU.

  • THANKS FOR ARRANGING THE DAY,

  • BEING A GREAT HOST AND ALSO

  • SHARING WITH ME YOUR RECENT AND

  • EXCITING WORK especially on

  • novel methods used Ford

  • measuring confirmational changes

  • in proximity with fret.

  • IT'SER EXCITING, I HOPE WE CAN

  • COLLABORATE AS A RESULT OF THAT.

  • PLEASURE TO BE HERE WITH YOU

  • TODAY.

  • I'M GOING TO AS THE TITLE

  • SUGGESTS, TALK ABOUT THE PROCESS

  • OF SYNCHRONOUS NEUROTRANSMITTER

  • RELEASE.

  • THERE'S BEEN A LOT OF PROGRESS

  • OVER THE LAST FIVE YEARS I WOULD

  • SAY ESPECIALLY IN BEGINNING TO

  • UNDERSTAND THE MECHANISM BY

  • WHICH THIS VERY IMPORTANT

  • PHYSIOLOGICAL PROCESS OCCURS IN

  • STRUCTURAL AND BIOCHEMICAL

  • TERMS.

  • SO WHAT I WOULD LIKE TO DO TODAY

  • IS OFFER SOME HISTORICAL

  • BACKGROUNDS TO THE THE PROBLEMS

  • AND THEN AFTER THAT SHARE WITH

  • YOU OUR CURRENT VIEW IN THE FORM

  • OF A MODEL OF HOW A SYNCHRONOUS

  • TRANSMISSION NEUROTRANSMITTER

  • RELEASE MAY WORK.

  • A STRUCTURAL BUOY CHEMICAL MODEL

  • AND AFTER THAT SHOW YOU SOME OF

  • THE EVIDENCE ACCUMULATED FOR THE

  • MODEL OVER THE LAST TWO OR THREE

  • YEARS ESPECIALLY.

  • WHAT DO I MEAN BY SYNCHRONOUS

  • NEUROTRANSMITTER RELEASE?

  • IT'S ACTUALLY THE PHYSIOLOGISTS

  • HAVE VARIOUS COMPLEX SCHEMES TO

  • MEASURE IT AND WAYS OF DEFINING

  • IT.

  • TO ME IT'S VERY SIMPLE BUT

  • FUNDAMENTAL CONCEPT IN

  • NEUROSCIENCE WHICH IS WHEN THE

  • ACTION POTENTIAL COMES DOWN THE

  • END OF THE NERVE AND YOU RELEASE

  • A NEUROTRANSMITTER ACROSS A

  • SYNAPSE TO THE NEXT NERVE OR

  • PERHAPS MUSCLE CELL, THE

  • NEUROTRANSMITTER NEEDS TO BE

  • RELEASED AT THE RIGHT TIME.

  • WE DIDN'T WANT THE

  • NEUROTRANSMITTER TO BE RELEASED

  • ASYNCHRONOUSLY ON ITS OWN ACCORD

  • BECAUSE IN THAT CASE IT'S A

  • FALSE ALARM.

  • YOU ALSO DON'T WANT THE

  • NEUROTRANSMITTER TO GO NOT BEING

  • RELEASED BECAUSE YOU MISSED AN

  • IMPORTANT SIGNAL.

  • IN FACT WHAT YOU WANT, YOU WANT

  • THE NEUROTRANSMITTER TO BE

  • RELEASED PRECISELY SYNCHRONOUSLY

  • WITH THE ARRIVAL OF ACTION

  • POTENTIAL AT SYNAPTIC TERMINAL.

  • THE WAY THAT'S ACHIEVEED IS

  • THROUGH MEMBRANE GATED CALCIUM

  • CHANNELS, PROBABLY EVERYONE

  • KNOWS THAT ARE LOCALIZED IN THE

  • SYNAPTIC PRE-SYNAPTIC REGION

  • THAT OPENED UP THE GATE FOR

  • CALCIUM ENTRY AND IT ACTS AS A

  • SECOND MESSENGER TO TRIGGER

  • RELEASE OF NEUROTRANSMITTER

  • STORED IN VESICALES.

  • THE PROBLEM THAT WE HAVE TAKEN

  • ON THAT I WOULD LIKE TO ADDRESS

  • HERE IS NUMBER ONE HOW ARE THESE

  • VESICLES RELEASED?

  • HOW DO THEY FUSE WITH THE

  • SURROUNDING MEMBRANE HAVING

  • STORED THE NEUROTRANSMITTER

  • WITHIN THEMSELVES.

  • HOW DO THEY DO IT SO RAPIDLY?

  • SO MUCH MORE RAPIDLY, ORDERS OF

  • THE MAGNITUDE MORE RAPIDLY.

  • THAN OTHER MEMBRANE FUSION

  • PROCESSES THAT TAKE PLACE IN THE

  • CELL.

  • SO THOSE ARE THE ASPECTS BUILT

  • INTO SIN CROW IN THISTY.

  • IT'S OBVIOUSLY IMPORTANT AT A

  • GROSS LEVEL.

  • IN YOUR BRAIN IF YOUR

  • NEUROTRANSMITTERS WERE RELEASED

  • HEALTHER SETTLER, THERE WOULD BE

  • NO POSSIBILITY OF C9

  • INFORMATION PROCESSING OR

  • ANYTHING OF ANY REMOTE INTEREST.

  • YOU WOULD HAVE A -- THINK ABOUT

  • WHAT EXPERIENCE WOULD BE IF YOUR

  • VESICALES ALL FUSED AS THEY

  • SHOULD BECAUSE THE FUSION

  • PROTEINS ARE CONSTITUTIVELY

  • ACTIVE.

  • THEY SHOULD FUSE AND RELEASE

  • NEUROTRANSMITTER ALL AT ONCE SO

  • THEN YOU HAVE EVERY

  • NEUROTRANSMISSION TAKING PLACE

  • AT ONCE WITHIN A SHORT PERIOD OF

  • TIME, NO THOUGHTS WHATSOEVER OR

  • PERHAPS EVERY THOUGHT YOU WOULD

  • HAVE AND NOT BE ABLE TO

  • COMMUNICATE TO EVERYONE ELSE, IT

  • MIGHT BE AN INTENSELY

  • TRANSFORMATIONAL EXPERIENCE BUT

  • IT WOULD BE ONE THAT LASTS 10

  • MILLISECONDS.

  • SO THAT CLEARLY DOESN'T HAPPEN.

  • IN A MUCH MORE SUBTLE LEVEL THE

  • SPEED OF SYNAPTIC TRANSMISSION

  • IS VERY IMPORTANT FOR THE

  • COMPLEX CIRCUITS THAT WE HAVE.

  • IT TYPICALLY TAKES A FEW

  • MILLISECONDS FOR A SIGNAL TO BE

  • TRANSPORTED ACROSS A SYNAPSE OF

  • WHICH THE RELEASE PROCESS,

  • INITIATION OF IT TAKES TYPICALLY

  • LESS THAN A MILLISECOND IN

  • CENTRAL SYNAPSES.

  • THAT'S ACTUALLY VERY IMPORTANT

  • BECAUSE FROM THE TIME THAT A

  • PRIMARY PIECE OF POTENTIAL

  • COGNITIVE INFORMATION LIKE

  • VISUAL FIELD AND AUDITORY

  • PATTERN WHAT HAVE YOU, IS

  • SENTENCED BY OUR INPUT OUTPUT

  • DEVICES, IT HAS MAYBE 20 OR 30

  • MILLISECONDS FOR ALL THOSE

  • PATTERNS COALESCE AT YOUR

  • HIGHEST CENTERS HAVING BEEN

  • TRANSMITTED THROUGH PERHAPS TEN

  • OR 15 DIFFERENT SYNAPSES.

  • I THINK WE'RE ALL FAMILIAR WITH

  • SOME ANYWAY ARE OLD ENOUGH TO

  • REMEMBER WHAT MOVIES USED TO BE

  • LIKE WHERE THE FILM GOES BY AND

  • YOU HAVE 35, THE MAGIC NUMBER

  • FRAMES PER SECOND.

  • WHY 35?

  • BECAUSE IF IT'S FASTER THAN 35

  • IT LOOKS LIKE A CONTINUUM TO

  • YOU.

  • IF IT'S SLOWER THAN 35, YOU SEE

  • SEPARATE PICTURES.

  • HOLLYWOOD FOLKS WEREN'T SPEND

  • THRIFTS THEY WERE LOOKING FOR

  • PROFITS, SO THEY FIGURED OUT

  • THAT THE GRANULARITY OF HUMAN

  • EXPERIENCE IS ABOUT 25 OR 30

  • MILLISECONDS.

  • SO YOU CAN GET BY WITH THE LEAST

  • NUMBER OF PHOTOGRAPHIC FILM AT

  • THAT SPEED.

  • SO THAT 25, 30 MILISEDGES IS

  • WHAT YOU HAVE THAT REPRESENTS

  • SIN CROW IN THISTY AND THE JOB

  • IS TO GET THROUGH 10, 15

  • SYNAPSES AND PLOW THROUGH THEM

  • FROM HERE AND HERE UP TO HERE.

  • FAST ENOUGH.

  • HOW DOES THAT WORK IN MOLECULAR

  • TERMS?

  • THAT'S THE PROBLEM I WOULD LIKE

  • TO THE ADDRESS TODAY.

  • THE SOLUTION TO THIS PROBLEM HAS

  • COME I WOULD SAY OVER SEVERAL

  • DECADES, ACTUALLY MORE LIKE HALF

  • A CENTURY, MANY WHICH CELL

  • BIOLOGY AND NEUROSCIENCE OR

  • NEUROPHYSIOLOGY AS IT WAS THEN

  • CALLED DOVE TAILED TOGETHER,

  • GONE APART COME BACK TOGETHER

  • AND THERE'S MANY CRITICAL COMING

  • TOGETHERS OF THESE TWO FIELDS.

  • THE BEGINNING OF THIS FIELD IN

  • FACT REFLECTED THAT.

  • GOING BACK TO THE CLASSIC WORK

  • OF FAT AND CAT WHO FOUND HOST

  • SYNAPTIC POTENTIALS, THE

  • NEUROMUSCULAR JUNCTION IN

  • CLASSICAL EXPERIMENTS FROM

  • 1950s, IF YOU HAVE AN

  • ELECTRICAL IMPULSE STIMULATING

  • THE NERVE INNER INVESTIGATING

  • THE MUSCLE, WHEN YOU GET

  • SYNAPTIC TRANSMISSION THE

  • MEMBRANE POTENTIAL OF THE MUSCLE

  • CHANGES IN RESPONSE.

  • IN YOU HAVE NO INPUT NO ACTION

  • POTENTIAL, ON THE MUCH SMALLER

  • SCALE THERE'S MINIATURE

  • POTENTIALS OR MINIS THAT APPEAR

  • AT FAIRLY LOW FREQUENCY BUT YOU

  • CAN SEE THAT THEY'RE ABSOLUTELY

  • MEASURABLE AND SEEM TO BE OF

  • UNIFORM SIZE MEASURED AS A POST

  • SYNAPTIC POTENTIAL.

  • IN THAT CAPS THE IDEA

  • TRANSFORMATIONAL IDEA THAT

  • SYNAPTIC TRANSMISSION THE

  • RELEASE OF NEUROTRANSMITTERS

  • OKAY CANS IN A JUAN UNTIL

  • FASHION WHICH THERE ARE

  • INDIVIDUAL PACKETS OF

  • NEUROTRANSMITTER SOMEHOW

  • PREARRANGED STORED AT A NERVE

  • ENDING SHOWN HERE.

  • ABILITY THE SAME TIME IN 1950s

  • MY PREDECESSOR AND FOUNDER OF

  • CELL BIOLOGY AT YALE, THE

  • FOUNDER TO LARGE DEGREE FIELD OF

  • CELL BIOLOGY OBSERVED THESE

  • MEMBRANE ENCLOSED VESICALES AT

  • NERVE ENDINGS.

  • HE CALLED THESE SYNAPTIC

  • VESICALES.

  • AND HE ALSO OBSERVED VESICALES

  • OF MANY KINDS IN THE CELL AND

  • CAME UP WITH THE IDEA THAT

  • VESICALES ARE CAPABLE OF

  • MEMBRANE FUSION.

  • SUGGESTED THAT THESE SYNAPTIC

  • VESICALES ARE IN FACT STORING

  • THE NEUROTRANSMITTER, A JUAN

  • UNTIL OF NEUROTRAN MITTER AND

  • MADE THAT CONNECTION IN

  • THE VESICAL HYPOTHESIS.

  • THE IDEA IS THAT THESE VESICALES

  • FUSE AFTER STIMULATION AND IT

  • WAS CAPTURED DISCOVERED THAT THE

  • ENTRY OF CALCIUM INTO THE --

  • THAT'S NEURONS SYNAPSES LIKELY

  • PROVIDES THE IMMEDIATE TRIGGER.

  • MORE MODERN WORK THROUGH THE

  • 1970s, IN FACT CONDUCTED HERE

  • AT NIH BY REECE AND HOUSER THIS

  • VESICAL HYPOTHESIS RECEIVE

  • STRONG SUPPORT WHERE THEY

  • OBSERVE VESICALES LIKE THIS, IN

  • FACT WERE SEEN FUSING WITH THE

  • PRE-SYNAPTIC PLASMA MEMBRANE

  • RELEASING THE NEUROTRANSMIT INTO

  • THE SYNAPTIC CLEFT TO DIFFUSE

  • ACROSS THE SYNAPSE.

  • HERE THEN IS ONE OF THE EARLY

  • COMING TOGETHERS OF CELL BIOLOGY

  • AND NEUROPHYSIOLOGY IN THE

  • VESICAL HYPOTHESIS.

  • THIS VIEW THAT VESICALES CAN

  • STORE COMPOUNDS FOR RELEASE FROM

  • THE CELL, WHICH AS JUSTIN SAID

  • GOES BY THE NAME OF EXOCYTOSIS

  • BUT INDEPENDENTLY REACHED AND

  • GENERALIZED BY PILATI AND

  • COLLEAGUES.

  • THERE ARE MUCH LARGER VESICLES

  • THAT STORE INSULIN OR IN THIS

  • CASE EXOCRINE SECRETIONS MANY

  • THE PANCREAS THAT ARE READY TO

  • BE RELEASED AND THEN ARE

  • RELEASED.

  • FOLLOWING A STIMULATION.

  • WHAT THIS INTRODUCES IS A

  • GENERAL CONCEPT WHICH IS VEST IT

  • WILLS STORE PRODUCTS THAT NEED

  • TO BE RELEASED RAPIDLY.

  • MUCH MORE RAPIDLY THAN THEY CAN

  • BE SYNTHESIZED OR LOCALIZEED TO

  • THE SITE OF RELEASE.

  • AND THAT THIS OCCURS

  • PHYSIOLOGICALLY.

  • IN NO PLACE IS THIS KINETIC

  • DEMAND FASTER THAN IN THE BRAIN.

  • FOR THE REASONS THAT I

  • MENTIONED.

  • PROBABLY SECOND FASTERS IS THE

  • RELEASE OVINES -- FASTEST IS

  • RELEASE OF INSULIN, SECONDS TO

  • COUPLE OF MINUTES.

  • MORE LEISURELY IS THE PROCESS OF

  • MEMBRANE FUSION AS IT OCCURS

  • WITHIN THE CYTOPLASM.

  • AND INDEED WORK IN THE 1970s,

  • 1980s AS WE BEGAN TO DISCOVER

  • RANGE OF VESICALES THAT TRAVERSE

  • THE CYTOPLASM CARRYING CARGO BY

  • BUDDING AND FUSION FROM ONE

  • COMPARTMENT TO ANOTHER WE NOW

  • RECOGNIZE AT LEAST A DOZEN, SOME

  • SPECIALIZED CELLS PROBABLY MORE

  • TYPES OF VESICALES EACH SELECTS

  • FOR A CARGO AND NEEDS TO DELIVER

  • THAT BY MEMBRANE FUSION WE CAME

  • TO REALIZE THIS PROCESS OF

  • MEMBRANE FUSION IS REALLY

  • GENERAL.

  • NOT JUST WITHIN A SINGLE CELL

  • CYTOPLASM THERE ARE PROBABLY TEN

  • OR 20 IN COMPLEX EUKARYOTIC

  • CELLS, TYPES OF MEMBRANE FUSION

  • THAT OCCUR, BUT ALSO GENERAL

  • BIOLOGY FROM PLANTS TO MICROBES

  • EUKARYOTIC MICROBES AND TO

  • HUMANS.

  • SO WHAT AGAIN BY WAY OF

  • BACKGROUND, THIS IS ALREADY BEEN

  • INTRODUCED, WHAT I PERSONALLY

  • FIND STILL QUITE ASTONISHING IS

  • THAT THIS ENTIRE ARRAY OF

  • PHYSIOLOGICALLY IMPORTANT

  • MEMBRANE FUSION PROCESSES FROM

  • THE SYNAPSE TO HORMONE RELEASE

  • TO THE COMPARTMENTAL

  • ORGANIZATION OF THE CYTOPLASM

  • AND IT PROPAGATION IN CELL

  • DIVISION, ARE ALL RELATE TO WORK

  • THE HANDIWORK OF A SINGLE FAMILY

  • OF PROTEINS.

  • THIS FAMILY OF PROTEINS CALLED

  • SNARE PROTEINS COMES IN A NUMBER

  • OF VARIETIES BUT THEY HAVE IN

  • COMMON PHICAL CHEMICAL MECHANISM

  • FOR MEMBRANE FUSION.

  • THERE ARE TWO TYPES OF SNARE

  • PROTEINS PHYSICALLY

  • COMPLIMENTARY TO EACH OTHER, WE

  • CALL THEM V AND T SNARES.

  • THEY EXIST IN -- THEY'RE

  • LOCALIZED DIFFERENTLY WITHIN THE

  • CELL.

  • A V SNARE PARTNERS A T SNARE AND

  • BRIDGES THE GAP BETWEEN TWO

  • MEMBRANES, AS I'LL DESCRIBE IN

  • STRUCTURAL TERMS IN A MOMENT NOT

  • ONLY INITIATE IT IS PROCESS OF

  • MEMBRANE FUSION, BILAYER FUSION

  • BUT ACTUALLY FUSES THE

  • BIOLAYERS.

  • BUT THERE ARE MANY DIFFERENT

  • TYPES OF V SNARES AND T SNARES

  • IN A CELL.

  • THEY'RE SHOWN HERE IN DIFFERENT

  • COLORS.

  • THE V SNARE ENCAPSULATED IN THE

  • VESICLE THAT DEPARTS THE

  • ENDOPALACE MIC RETICULUM CAN

  • ONLY MATE WITH COGNATE T SNARE

  • LOCATED AT THE ENTRY FACE OF THE

  • GOLGI.

  • THAT'S ONE OF THE SEVERAL

  • MOLECULAR FEATURES, NOT THE ONLY

  • FEATURE BUT A CRITICAL MOLECULAR

  • FEATURE THAT DICTATES FUSION OF

  • THIS VESICAL HERE, NOT THERE,

  • NOT ANY PLACE ELSE AND ALLOWS

  • SPECIFIC MEMBRANE TRAFFIC IN THE

  • CELL.

  • SIMILARLY THERE'S A DIFFERENT

  • BUT STRUCTURALLY RELATED

  • HOMOLOGOUS V SNARE PACKAGED TO

  • VESICALES LEAVING THE EXIT OF

  • THE GOLGI THAT FINDS ITS PARTNER

  • IN THE PLASMA MEMBRANE THAT'S A

  • DIFFERENT V AND T SNARE

  • DEPENDING WHICH SURFACE OF THE

  • CELL, APICAL OR BASAL LATERAL.

  • I COULD GO ON AND ON BUT I

  • WON'T.

  • SO THE SPECIFIC PAIRING OF

  • PROTEINS BETWEEN PARTNERED

  • MEMBRANES INCLUDING THE RELEASE

  • OF VESICALES AT THE CELL SURFACE

  • AS A SPECIAL CASE BUT A VERY

  • IMPORTANT SPECIAL CASE OCCURS.

  • ALL THESE PROCESSES ACCEPT

  • FUSION WITH THE PLASMA MEMBRANE

  • ARE WHAT CELL BIOLOGISTS CALL

  • CONSTITUTIVE PROCESS.

  • THEY OCCUR AL THE TIME.

  • THEY OCCUR THROUGHOUT THE CELL

  • CYCLE.

  • YES, THERE MAYBE REGULATION OF

  • ONE SORT OR ANOTHER, NO DOUBT

  • BUT THEY OCCUR ALL THE TIME.

  • THIS PUTS THEM INTO A

  • FUNDAMENTAL DISTINCTION WITH

  • CERTAIN CLASSES OF FUSION WITH

  • THE PLASMA MEMBRANE, EXOCYTOSIS,

  • WHICH ONLY OCCUR SOME OF THE

  • TIME WHEN SIGNAL IS PROVIDED AS

  • IN THE RELEASE OF

  • NEUROTRANSMITTER WHEN CALCIUM

  • ENTERS SECONDARY TO THE ARRIVAL

  • OF AN ACTION POTENTIAL.

  • TIME COURSE HERE IS RELATIVELY

  • LEISURELY FROM THE TIME A

  • VESICAL DOCKS TO FUSION

  • TYPICALLY TAKES TEN SECONDS TO A

  • MINUTE DEPENDING ON THE

  • SITUATION.

  • THAT'S THE TIME FRAME.

  • DIFFERENT THAN THE TIME FRAME IN

  • SYNAPTIC TRANSMISSION.

  • WHICH THE NEUROTRANSMITTER CAN

  • BE RELEASED AS FAST AS 200

  • MICROSECONDS FROM THE TIMECAL

  • YUM HAVES.

  • SO THAT IS THE CONTRA

  • DISTINCTION HERE.

  • WHAT CONFOUNDS THIS FURTHER IS

  • SNARE PROTEINS WHICH I'LL

  • DESCRIBE IN INCREASINGLY GREATER

  • DETAIL IN TERMS OF HOW THEY FUSE

  • BILAYER ARE INTRINSICALLY

  • POWERFUL FUSION PROTEINS THAT

  • ARE ON RATHER THAN OFF.

  • HOW CAN YOU HAVE A

  • NEUROTRANSMITTER VESICAL SITTING

  • RIGHT NEXT TO THE PRE-SYNAPTIC

  • MEMBRANE WITH POTENT FUSION

  • MACHINERY BY IN AND OF ITSELF IS

  • ON NOT OFF AND SOMEHOW DOESN'T

  • FUSE.

  • BUT THEN BUT THEN AT THE RIGHT

  • MOMENT IT FUSES RAPIDLY.

  • SOME ANSWERS BEGIN TO COME FROM

  • AN UNDERSTANDING OF THE

  • UNDERLYING PRINCIPLE OF MEMBRANE

  • FUSION.

  • ENCAPSULATED BETWEEN THE TWO

  • STRUCTURES.

  • THE SNARE PROTEINS ARE ALPHA

  • HELICAL BUNDLE PROTEIN,

  • RELATIVELY SMALL, THEY HAVE TWO

  • PARTS ALL A PART IN THE

  • MEMBRANE, A TRANSMEMBRANE AND

  • THEN THEY HAVE A HELIX FORMING

  • SO CALLED SNARE MOTIF THAT IS IN

  • THE CYTOPLASM.

  • THE V?úzBRE EMANATES PRIMARILY

  • FROM THE VESICAL, THAT'S WHY

  • IT'S CALLED THE V SNARE FOR

  • VESICLE AND CONSISTS OF A SINGLE

  • HELICAL PROTEIN CYTOPALACE MIC

  • DOMAIN.

  • THE T SNARE, STANDING FOR TARGET

  • MEMBRANE VESICLE FUSE WITH THE

  • PLASMA MEMBRANE, THE T SNARE

  • CONTRIBUTES THREE HELICES, WHEN

  • IT ASSEMBLES IT FORMS A FOUR

  • HELIX BUNDLE THAT FOUR HELIX

  • BUNDLE IS STABLE SO THAT IF YOU

  • ISOLATE THIS PROTEIN, THIS

  • COMPLEX FROM CELLS OR FROM BRAIN

  • OR FORM IT ARTIFICIALLY WITH

  • RECOMBINANT PROTEINS, YOU HAVE

  • TO FIND AND OTHERS FOUND OF

  • COURSE YOU HAVE TO HEAT THIS

  • PROTEIN TO ALMOST 100-DEGREES,

  • YOU HAVE TO BOIL THE WATER FOR

  • IT TO DENATURE THAT'S HOW STABLE

  • IT IS.

  • THERE'S A VERY INTERESTING

  • FEATURE.

  • THESE PROTEINS WANT TO FOLD THE

  • MAKE A FOUR HELIX BUNDLE BUT

  • THEY CAN'T DO THAT WHEN BETWEEN

  • TWO BILAYERS.

  • IT'S FROM THIS THE PRINCIPLE OF

  • FUSION FOLLOWS.

  • THE V SNARE UNIQUELY ASSEMBLING

  • FROM SYNAPTIC VESICAL.

  • THE T SNARE IS ASSEMBLING FROM

  • THE MAMA MEMBRANE.

  • AS THESE TWO ZIPPER UP FROM

  • MEMBRANE DISTAL END TERMINI

  • TOWARDS THE MEMBRANE, THEY CAN

  • ASSEMBLE BUT THEY CAN'T

  • COMPLETELY ASSEMBLE.

  • I HOPE EVERYBODY CAN SEE THAT.

  • LEFT TO THEIR OWN DEVICES,

  • REMOVED FROM MEMBRANE ENTIRELY,

  • THEY DO FULL WILL ASSEMBLE.

  • EVEN THE TRANS MEMBRANES FIND

  • EACH OTHER.

  • SO THEY WANT TO ZIPPER UP TO

  • THIS TIGHT FOUR HELIX BOPPED L

  • BUT THEY CAN'T.

  • WHY CAN'T THEY?

  • THEY TWO BILAYERS ARE SEPARATE.

  • THE ONLY WAY THESE TWO BILAYERS

  • BECOME ONE BILAYER CAN THE THEY

  • ZIPPER.

  • SO WHAT WE HAVE HERE IS

  • THERMODYNAMIC LINKAGE DUE TOSER

  • UK EXCLUSION OF TWO REACTIONS,

  • THE FIRST REACTION IS A PROTEIN

  • FOLDING REACTION.

  • THE V SNARE ESPECIALLY IS A

  • REASON DOCUMENT COIL AND THE T

  • SNARE WITH THREE SUBUNITS IS

  • LOOSELY AABLED BEFORE IT

  • EPICOUNTERS THE V SNARE.

  • IN THIS STATE THE SNARES ARE

  • PARTIALLY OR COMPLETELY

  • UNFOLDED.

  • IN THIS STATE AFTER FUSION IN

  • GOING FROM UNFOLDED TO

  • COMPLETELY FOLDED THERE'S A LOT

  • OF ENERGY POTENTIALLY RELEASED.

  • IF IT'S MIXED IN A DETERGENT

  • SOLUTION OR WATER, THEY WILL

  • GIVE THAT ENERGY OFF AS HEAT.

  • PLACED BETWEEN TWO BILAYERS IF

  • -- IT'S -- THEY WILL PROVIDE

  • ENOUGH ENERGY TO DO WORK ON THE

  • BILAYER TO CAUSE THE BILAYERS TO

  • FUSE.

  • OBVIOUSLY WE DON'TNESS EVERY

  • DETAIL ABOUT THAT TRANSMISSION

  • AND THERE'S A LOT OF IMPORTANT

  • WORK GOING ON, NOT THE LEAST

  • FROM JOSH ZIMMERBURG AND OTHERS

  • HERE.

  • AND THERE ARE A NUMBER OF

  • COMPETING MODELS BUT WHAT IS

  • CLEAR IS THE ASSEMBLY OF SNARES

  • CREATES AN INNER FORCE THAT PULL

  • IT IS MEMBRANES TOGETHER AND

  • THAT FORCE RESULTS IN OPENING OF

  • A FUSION PORE TO RELEASE THE

  • NEUROTRANSMITTER OR SOME

  • EQUIVALENT CARGO.

  • WE KNOW THIS OCCURS WITH

  • ISOLATED SNARE PROTEINS.

  • THE TIME COURSE IS MEASUREED IN

  • A NUMBER OF LABORATORIES, IT'S

  • LESS THAN 100 MILLISECONDS, IT'S

  • TYPICALLY MORE THE AVERAGE

  • MEASUREMENT IS PROBABLY 30 TO 50

  • MILLISECONDS.

  • IF YOU HAVE ISOLATED PROTEINS

  • WITH A V SNARE BILAYER THAT'S

  • THE TIME COURSE THE SNARES WILL

  • FUSE.

  • THEY ARE EXTREMELY COMPETENT.

  • RECENT STUDIES FROM

  • (INDISCERNIBLE) LAB AND WE

  • CONFIRMED THIS SHOW THAT A

  • SINGLE SNARE COMPLEX THAT'S

  • ASSEMBLING WE CALL IT A SNARE

  • PIN, WILL BE SUFFICIENT AT LEAST

  • AT A CERTAIN RATE ENERGETICALLY

  • SUFFICIENT TO DRIVE THE FUSION

  • OF A VESICLE WITH A BILAYER.

  • THESE ARE ENERGETICALLY

  • COMPETENT.

  • SO WE HAVE MEASURED THIS INNER

  • DIRECTED FORCE DIRECTLY USING

  • THE SURFACE FORCE APPARATUS

  • WHERE WE HAVE SNARES IN OPPOSITE

  • MEMBRANES BRING TOGETHER WITH

  • SUB-NANOMETER POSITION, PULL

  • THEM APPEARED IN A DEFINED WAY

  • AND MEASURE ADHESIVE FORCE.

  • IT IS A FORCE AND ENERGY

  • PERFECTLY CONSISTENT WITH THE

  • IDEA THAT A SINGLE SNARE PIN IS

  • ENERGETICALLY CAPABLE OF FUSING

  • A LIPID BILAYER.

  • FINALLY IN CASE SOMEONE ASKS AT

  • THE END OF THIS FUSION PROCESS

  • THERE'S AN ENZYME SYSTEM

  • INVOLVING THE TRIPLE AATPASE

  • CALLED NSF THAT UTILIZE A TP

  • HYDROLYSIS TO SEPARATE SNARES

  • UNFOLD AND ALLOW TO BE RECYCLED

  • ENERGETICALLY TO THE HIGH ENERGY

  • STATE OF UNFOLDED PROTEIN AND P

  • TO INITIATE RECYCLING TO THE

  • CORRECT DONOR COMPARTMENT.

  • THIS IS OUR CURRENT

  • UNDERSTANDING IN CARTOON LEVEL

  • ANYWAY HOW MEMBRANE FUSION

  • WORKS.

  • TO MAKE IT MORE CONCRETE I'LL

  • DRAW UPON A RECENT X-RAY CRYSTAL

  • STRUCTURE OF RYAN HART AND

  • COLLEAGUES, THAT SHOWS THE FOUR

  • HELIC BUNDLE.

  • THIS IS OF THE SYNAPTIC SNARE

  • PROTEIN.

  • BY WHICH OF INTRODUCTION THESE

  • ARE THE PROTEINS THAT DO THE JOB

  • TO RELEASE NEUROTRANSMITTER AT

  • SYNAPSES.

  • THE V SNARE CONSISTS OF A

  • PROTEIN CALLED VAMP OR

  • SYNAPTOBREVIN AND IT ORIGINATES

  • IN THE SYNAPTIC VESICAL.

  • THE T SNARE CONSISTS OF TWO

  • PROTEIN, INTEGRAL MEMBRANE

  • PROTEIN CALLED SYNTAXIN, AND

  • SOLUBLE PROTEIN CALLED SNAP 25

  • WHICH CONTRIBUTES TWO OF THE

  • HELICES.

  • SO THE T SNARE HERE CONSISTS OF

  • THREE HELICES, TWO CONTRIBUTED

  • BY SNAP 25 IN GREEN, ONE

  • CONTRIBUTED BY MEMBRANE PROTEIN

  • SEN TAX AND PLASMA MEMBRANE

  • INITIALLY AND THE OTHER THE

  • VESICLE PROTEIN VAMP INITIALLY

  • IN THE SYNAPTIC( VESICAL.

  • I WANT TO DISTINGUISH THREE

  • REGIONS, THERE IS A REGION

  • CALLED THE BUNDLE REGION OR THE

  • HELICAL BUNDLE REGION YOU CAN

  • SEE IT'S CALLED THAT FOR OBVIOUS

  • REASONS.

  • SNAP 25 TERMINATES AT THAT POINT

  • AND VAMP AND SYNTAX AND CONTINUE

  • TO INTERACT IN A REGION CALLED

  • THE LINKER REGION WHICH DOES NOT

  • INCLUDE CONTRIBUTIONS FROM SNAP

  • 25, THE LINKER BECAUSE IT

  • CONNECTS THE FOUR HELIX BUNDLE

  • TO THE MEMBRANE AND THEN YOU

  • HAVE THE TRANSMEMBRANE DOMAIN OF

  • V SNARE AND T SNARE.

  • VAMP AND SYNTAXIN.

  • THIS IS THE POST FUSION STATE

  • THAT EXISTS AFTER THE FUSION.

  • IF WE WANT TO UNDERSTAND THE

  • MECHANISM OF FUSION MORE WE NEED

  • TO UNDERSTAND FOR ABOUT

  • STRUCTURE AS ASSEMBLING RATHER

  • THAN AFTER ASYSTEMBLY BUT THIS

  • PROVIDES OOH VERY IMPORTANT

  • GUIDE.

  • IMPORTANT LIT IT SHOWED SCRATCH

  • AND SYNTAXIN CONTINUE THE

  • INTERACT WITH A SERIES OF

  • CONTACTS INTO THE BILAYER, EVEN

  • AFTER FUSION.

  • THIS ZIPPERING PROCESS EVIDENTLY

  • PROCEEDS RIGHT THE WAY THROUGH

  • THE FUSION PROCESS.

  • NOW, IF I DIDN'T GET ANYTHING

  • ACROSS HERE, I WOULD LIKE TO

  • TAKE A MOMENT AND SUMMARIZE 25

  • YEARS OF MY LIFE IN THIS ONE

  • SLIDE WHICH EXPLAINS HOW I THINK

  • ABOUT THE PROBLEM.

  • I HOPE NOBODY IS OFFENDED.

  • THIS IS A READY'S HAIR PIN.

  • ANY OF YOU WHO HAVE HAD THE

  • EXPERIENCE OF TRYING TO SEPARATE

  • THE TWO ENDS OF A LADY HAIR PIN

  • WILL KNOW THAT IT TAKES WORK TO

  • DO THAT.

  • SO LET'S IMAGINE THIS IS A SNARE

  • PIN ASSEMBLING BETWEEN TWO

  • VESICALES EXPECT E START WHEN

  • IT'S ASSEMBLED, NOW WE PULLED IT

  • APART.

  • HAVING PULLED IT APART, WE'RE

  • GOING TO INSERT EACH END INTO A

  • RUBBER BALL REPRESENTING TWO

  • VESICALES OR IF YOU WILL, A

  • SYNAPTIC VESICAL AND PLASMA

  • MEMBRANE.

  • NOW WHAT WE'RE GOING TO DO IS

  • LET THEM GO.

  • AS WE LET THIS GO WHAT HAPPENS?

  • THE PIN BECAUSE IT WAS RESTORING

  • FORCE INWARD DIRECTED FORCE

  • THAT'S THE FORCE I'M REFERRING

  • TO THAT OCCURS BETWEEN SNARE

  • PINS.

  • IT WILL -- WHAT WILL THIS PIN

  • DO?

  • IT WILL FORCE TOGETHER TWO

  • RUBBER BALLS.

  • THAT'S THE END OF IT IF IT'S

  • RUBBER BALLS BUT IF THEY'RE NOT

  • THEY HAVE A LIQUID LIKE

  • CHARACTER WHICH IN PHICAL TERMS

  • MEANS THEY HAVE SURFACE TENSION

  • THAT CAN BE OVERCOME EXERTED BY

  • THE PIN, THE SNARE PIN IN

  • REALITY, THEN THE TWO BALLS WILL

  • BE BLENDED INTO ONE WHICH ALLOWS

  • THE PIN TO REACH ITS BROWN STATE

  • AND P ITS MINIMUM ENERGY STATE.

  • IN MY VIEW TRAINLY FUSION IS

  • NOTHING MORE OR ANYTHING LESS

  • THAN THIS.

  • THERE ARE A LOT OF DEBATES ABOUT

  • THE TRANSITION STATE WHEN THOSE

  • TWO BALLS ARE ABOUT TO GO

  • TOGETHER.

  • AND I TEND TO LOOK AT THAT AS A

  • STATISTICAL MECHANICAL DEBATE OF

  • INTEREST.

  • FROM A BIOLOGICAL POINT OF VIEW

  • HOWEVER, OF GREATER INTEREST IS

  • THE THERM MOW DYNAMICS THAT A

  • PRE-CONDITION IS CREATED THAT

  • MAKES THE FUSION INEVITABLE.

  • THIS EXAMPLE IS NOT AN IDOL ONE,

  • IN RECENT MONTHS MY COLLEAGUES

  • GRABBED OUR HANDS ON INDIVIDUAL

  • SNARED COMPLEXES AN LITERALLY

  • PRIED THEM APART WITH OPTICAL

  • TWEEZERS.

  • SO HERE WHAT A COLLEAGUE IN CELL

  • BIOLOGY IN HIS LAB AND WHAT WE

  • HAVE DONE IS TO ATTACH A SMALL

  • BEAD BY MOLECULAR MODIFICATION

  • TO THE ASSEMBLED END OF A SNARE

  • COMPLEX.

  • WE ARTIFICIALLY CROSS LINK THE V

  • AN T SNARE, THE SAME SNARES YOU

  • SAW A MOMENT AGO, AND WE

  • ARTIFICIALLY CONNECTED THEM AT

  • THEIR MEMBRANE DISTAL END

  • TERMINI.

  • THE ATTACHMENTS WOULD BE HERE.

  • THE ANCHORS ARE REMOVED AND

  • REPLACED BY A LINKER TO ONE BEAD

  • AND LINKER TO THE OTHER ON VAMP

  • AND SYNTAXIN.

  • NOW WHAT WE CAN DO WHAT I

  • ILLUSTRATED A MOMENT AGOND PULL

  • ON THEM IN A DETERMINED WAY.

  • WHAT WE OBSERVE IS AS WE DO THEY

  • MELT LAYER BY LAYER.

  • THE FIRST THING THAT MELTS IS

  • THE LINKER LAYER.

  • THE SECOND THING THAT MELTS IS

  • HALF OF THE FOUR HELIX BOPPED L.

  • AND NULL REVERSIBLY SO AS YOU

  • PULL YOU GET WHAT A SINGLE

  • CHANNEL FIZZ IDEAL GIST WOULD

  • RECOGNIZE A SINGLE CHANNEL

  • BEHAVIOR.

  • BECAUSE THE LINKER HAS BEEN

  • DESTABILIZED AND CERTAIN FORCE

  • LEVELgÑ" FLUCTUATES BETWEEN OPEN

  • CLOSED, OPEN CLOSED.

  • AS IT OPENS THE DISTANCE BETWEEN

  • THE TWO BEADS INCREASES AND

  • THAT'S WHAT WE'RE MEASURING

  • HERE.

  • THIS WILL GO ON FOREVER UNLESS

  • WE EXERT MORE FORCE AND WE GET

  • TO THE NEXT FORCE LEVEL WE GO TO

  • THE NEXT PORTION WHICH

  • FLUCTUATES BECOME AND FORTH.

  • ONE BEAUTY OF THIS EXPERIMENT

  • BESIDES DEMONSTRATING THE BINARY

  • LIKE SWITCH NATURE OF DOMAINS IS

  • IT ALLOWS US TO MEASURE KINETICS

  • WITH WHICH THIS FLIPPING BACK

  • AND FORTH OCCURS.

  • REMARKABLY ENOUGH FOR THE

  • SYNAPTIC SNARE COMPLEX THE RATE

  • OF REZIPPERRING HERE OCCURS WHAT

  • WE ESTIMATE TO BE A DEIFYING

  • CONTROLLED LIMIT.

  • -- DIFFUSION CONTROLLED LIMIT.

  • AS FAST AS THE V SNARE ZIPPERS

  • IN AND P LAYS DOWN, BY

  • DISPLACING WATER, THAT'S HOW

  • FAST IT MOVES.

  • THIS MACHINE IS NOT ONLY NEE

  • JETTICLY SUFFICIENT FOR FUSION

  • BUT -- ENERGETICALLY FOR FUSION

  • BUT DESIGNED AS FAST AS PHYSICS

  • ALLOW WHICH IS A WONDERFUL FACT

  • WHEN WE CONSIDER HOW FAST

  • SYNAPTIC VESICLE RELEASE HAS TO

  • OCCUR, THE TWO HUNDRED

  • MICROSECONDS.

  • I WANTED YOU TO KNOW THAT THERE

  • IS A PAUSE IN THE DISASSEMBLY.

  • WE BUST THIS PART, BUST THAT

  • PART AND IF WE PULL HARDER WHICH

  • IS NOT SHOWN HERE WE PULL THE

  • LAST PART CALLED THE END

  • TERMINAL DOMAIN, LINKER DOMAIN,

  • END TERMINAL DOMAIN IS LAST,

  • THERE'S THE GUY THAT ASSEMBLES

  • FIRST WHEN THE VESICAL STARTS

  • DOCKING.

  • THAT TURNS OUT TO BE VERY, VERY

  • SLOW.

  • IT'S VERY SLOW, MEASURED

  • ACTUALLY RATE CONSTANT IS

  • MEASURED ON THE ORDER OF AN

  • HOUR.

  • THE REASON IT'S SO SLOW IS BY

  • BEING SO SLOW IT ALLOWS OTHER

  • FACTORS TO KICK IN THAT CAN

  • REGULATE THE DOCKING OF THE

  • VESICAL.

  • SO YOU HAVE FACTORS UPSTREAM AND

  • YOU'LL SEE THAT REGULATE DOCKING

  • OF THE VESICAL TO ALLOW IT TO

  • ZIPPER THROUGH THE END TERMINAL

  • DOMAIN.

  • I'LL GIVE THE STORY AWAY NOW

  • BECAUSE YOU'LL SEE THAT IN THE

  • SPECIAL CASE OF THE SYNAPTIC

  • VESICAL, THE VESICAL IS FROZEN

  • AT THIS STAGE.

  • HALFWAY ZIPPERED PUNT WAITED BY

  • -- ONCE WAITED BY IONIC LAYER,

  • THESE ARE HOPE TAB REPEATS, AND

  • THOSE A CERTAIN IN EVERY SNARE

  • COMPLEX IS REPLACED BY

  • HYDROPHYLIC RESIDUE.

  • THIS CAUSES AN INTENTIONAL PAUSE

  • HALFWAY THROUGH THE ZIPPERING

  • PROCESS.

  • AND IN THE SYNAPSE THERE ARE

  • OTHER PROTEINS AND I WILL

  • DESCRIBE THEM TO YOU, THAT GRAB

  • THE SNARE COMPLEX QUITE

  • LITERALLY, AT THIS PAUSE POINT

  • AND FREES IT UNTIL THE ACTION

  • POTENTIAL ARRIVES, UNTIL CALCIUM

  • ARRIVES.

  • AND THAT IS REALLY NIFTY BECAUSE

  • IT ALLOWS THE SNARE COMPLEX TO

  • BE ACTIVATED FROM A VESICAL

  • WHOSE FRAME IS FROZEN JUST

  • BEFORE MEMBRANE FUSION CAN BE

  • COMPLETED AT A DIFFUSION

  • CONTROLLED LIMIT.

  • THAT IS OUR PICTURE OF HOW THIS

  • WORKS.

  • TO SUMMARIZE THEN, THERE IS IN

  • THE ASSEMBLED SNARE COMPLEX

  • DISCREET DOMAINS, END TERMINAL,

  • C TERMINAL DOMAIN, AND

  • TRANSMEMBRANE DOMAIN.

  • THEY HAVE DISTINCT FUNCTIONS.

  • THE PURPOSE OF THE THE END

  • TERMINAL DOMAIN WHICH ASSEMBLES

  • FIRST IS TO DOCK THE VESICAL

  • TIGHTLY TO THE PLASMA MEMBRANE.

  • THE NEXT ASSEMBLY OF THE C

  • TERMINAL DOMAIN IRREVOCABLY

  • COMMITS THE VESICLE TO FUSE.

  • THE ACTUAL FUSION OCCURS AS BEST

  • WE CAN JUDGE SUMMARIZING WORK

  • FROM MY LAB AND RYANHART YAN'S

  • LAB HERE WHEN LINKER DOMAIN

  • ASSEMBLABLES.

  • THEN THE TRANSMEMBRANE DOMAIN IS

  • BELIEVE TO HAVE ASSEMBLED BY THE

  • X-RAY CRYSTALOGRAPHY.

  • SINCE THE FUSION OF THE BILAYERS

  • MEASURED BY ZIPPERING --

  • TRIGGERED BY LINKER DOMAIN

  • ZIPPERING AND THE MIXING OF THE

  • LIPID BILAYER AND THE INITIAL

  • OPENING OF THE FUSION PORE, ALL

  • THIS WOULD SEEM TO BE OVER SO IT

  • WOULD SEEM TO BE NO ROLE

  • NECESSARILY FOR THE ZIPPERING OF

  • THE TRANSMEMBRANE DOMAIN BUT

  • ACTUALLY NOTHING COULD BE

  • FURTHER FROM THE TRUTH BECAUSE

  • AS WE RECENTLY PUBLISHED, THE

  • ZIPPERING OF THE TRANSMEMBRANE

  • DOMAIN AFTER FUSION HAS

  • OCCURRED, AFTER THE FUSION PORE

  • JUST OPENS SEEMS CRITICAL BASED

  • ON IN VITRO EMPERIMENTS FOR THE

  • OPENING OF THE FUSION PORE,

  • EXPANSION OF THE FUSION PORE.

  • I WON'T REALLY HAVE TIME TO GO

  • INTO THIS IN DETAIL BUT IF

  • YOU'RE INTERESTED THIS WAS VERY

  • REISN'TLY PUBLISHED IN SCIENCE,

  • LAY SHI IS THE PERSON WITH THE

  • MOST WORK ON THIS IN THE LAB.

  • IT INVOLVES A NOVEL ASSAY IN

  • WHICH WE MEASURE THE FUSION OF

  • SNARE CONTAINING ARTIFICIAL

  • VESICALES WITH V SNARE CON

  • TAPING VESICALES WITH T SNARE

  • CONTAINING NANODISC.

  • IT OPENS A HOLE DURING THE

  • FUSION PROCESS SO WE CAN MEASURE

  • RELEASE OF CONTENT AS A PROXY

  • FOR THE OPENING OF A FUSION

  • PORE.

  • WE ON SERVE IN NO INSTANCE IS

  • THERE A BIG DIFFERENCE, YOU GET

  • LIPID MIXING WITH OR WITHOUT THE

  • VARIOUS MUTATIONS I DESCRIBE BUT

  • GOING TO RYAN HART'S STRUCTURE

  • WHEN WE MUTATE KNOWN CONTACTS IN

  • HIS CRYSTAL STRUCTURE BETWEEN

  • THE VAMP AND SYNTAXIN

  • TRANSMEMBRANE ANCHORS WE GET

  • SLOW OPENING OF THE FUSION PORE

  • THOUGH FUSION OCCURRED WITH THE

  • NORMAL SPEED.

  • THE LINKER DOMAINS ARE INTACT,

  • THE BILAYERS ARE FUSED.

  • YOU CAN'T HAVE TOP LOGICAL

  • FUSION WITHOUT SOME OPENING OF

  • THE FUSION PORE SO YOU GET SOME

  • RELEASE BUT THE RATE OF RELEASE

  • IS DRASTICALLY INCREASED.

  • IF YOU MUTATE THE NON-CONTACT

  • RESIDUES WE'RE SHOWING ONLY A

  • COUPLE HERE BUT WE HAVE DONE IT

  • EXHAUSTIVELY, EVERY MOLECULAR

  • CONTACT OBSERVED HERE IS

  • IMPORTANT FOR OPENING OF THE

  • FUSION PORE.

  • SO WE'RE NOW TURNING TO

  • PHYSIOLOGICAL SYSTEMS TO SEE IF

  • THIS IS PHYSIOLOGICALLY RELEVANT

  • BUT CERTAINLY SUGGESTS THAT EACH

  • DOMAIN OF THE SNARE COMPLEXIN

  • COLLUDING THE TRANSMEMBRANE HAS

  • A CRITICAL ROLE.

  • SO NOW I WOULD LIKE TO

  • ENCAPSULATE THIS IN ONE MORE

  • VIDEO.

  • SO HERE WE HAVE

  • NEUROTRANSMITTERS STORED IN A

  • SYNAPTIC VESICAL.

  • AND THE REASON I WOULD LIKE TO

  • SHOW YOU THIS THOUGH IT'S PREPPY

  • SHUTS, IT WILL OR YEN YOU TO

  • WHAT'S NEXT WHICH IS A LITTLE

  • MORE DIFFICULT.

  • SO HERE WHAT WE HAVE IS THE T

  • SNARE IN THE PLASMA MEMBRANE AND

  • IN THE INITIAL STEP -- STATE

  • WHERE THE VESICAL IS DOCKED THE

  • END TERMINAL PORTION OF THE V

  • SNARE VAMP IS HELIX.

  • IT'S HELICAL STATE HALF ZIPPERED

  • THROUGH THE HELICAL BUNDLE SO TO

  • SPEAK HALFWAY FORMED.

  • BUT THE REMAINDER OF THE V SNARE

  • INCLUDING C TERMINAL HALF THAT

  • WILL FORM THE BUNDLE AND LINKER

  • PORTION HAS NOT YET ZIPPERED.

  • WE BELIEVE FOR REASONS YOU'LL

  • SEE THAT THAT IS THE POINT AT

  • WHICH SYNAPTIC TRANSMISSION IS

  • PAUSED TO ALLOW SIN CROW IN

  • THISTY.

  • SIN CROW IN THISTY RESULTS

  • BECAUSE THE -- SIN CROW IN

  • THISTY RESULTS BECAUSE IT IS

  • ACCUMULATED AND THEREFORE BEEN

  • RELEASED SYNCHRONOUSLY.

  • IF THEY'RE IN THE ACCUMULATED AT

  • A DEFINED STAGE THEY CANNOT BE

  • RELEASED SYNCHRONOUSLY.

  • IT'S FUNDAMENTAL TO THE PROCESS.

  • NEXT THING THIS IS IN THE

  • ABSENCE OF REGULATION, THE

  • GENERAL FUSION PROCESS AS WE

  • UNDERSTAND IT, IS THAT THE C

  • TERMINAL PORTION OF THE VAMP

  • ZIPPERS, THIS IS WHAT COMMIT TO

  • FUSION.

  • THEN THE LINKER ZIPPERS, AS THE

  • ZIPPERS OPENS UP THE FUSION PORE

  • INITIALLY BUT ONLY SO FAR.

  • THEN FINALLY AS THE

  • TRANSMEMBRANE ZIPPER, THIS

  • DRIVES WE THINK IT PRODUCES A

  • RADIAL FORCE SO WE DON'T REALLY

  • KNOW THIS, IT'S SPECULATION,

  • LITERALLY FORCE IT IS FUSION

  • PORE OPEN.

  • THAT'S OUR VIEW OF MEMBRANE

  • FUSION FROM THE POINT OF VIEW OF

  • THE PROTEINS.

  • NOW I WILL LIKE TO COME BACK

  • WITH BACKGROUND TO THE VERY

  • SPECIFIC PROBLEM, HERE YOU HAVE

  • A VESICLE, IT HAS IN VIVO A MUCH

  • HIGHER CONCENTRATION OF V SNARES

  • THAN ANY IN VITRO SYSTEMS.

  • WE MIGHT TYPICALLY WORK WITH

  • FIVE, TEN VAMPS IN AN ARTIFICIAL

  • VESICAL OF THIS SIZE IN VITRO.

  • BUT THE V SNARE HERE WAS PRESENT

  • AT 70 COPIES PER VESICAL.

  • THE T SNARE SYNTAXIN IS PRESENT

  • AT PERHAPS ONE COPY FOR EVERY

  • THOUSAND PHOSPHOLIPID MOLECULES

  • IN THE ARTIFICIAL BILAYERS WE

  • USE.

  • HERE IT'S PRESENT IN CLUSTERS

  • THAT ARE ALMOST PURE WITH

  • RESPECT TO SYNTAXICSN ACCORDING

  • TO THE LATEST WORK.

  • REMARKABLY ENOUGH THESE

  • VESICALES STAY WHERE THEY ARE,

  • THEY DON'T FUSE, EVEN THOUGH IF

  • YOU TAKE SAME PROTEINS OUT OF

  • THE SYNAPSE, YOU PUT THEM INTO

  • BILAYERS AT LOWER

  • CONCENTRATIONS, WITHIN 50, 100

  • MILISECONDS THEY HAVE FUSED.

  • I HAPPEN TO BE A BELIEVER IN

  • PHYSICS.

  • I HAPPEN TO BELIEVE THAT PHYSICS

  • DOESN'T DISAPPEAR WHEN YOU BUT

  • MOLECULES TO A CELL.

  • THE BIOPHYSICS REPRESENTS THE

  • GROUND TROOP OF WHAT A PROTEIN

  • CAN DO.

  • THAT GROUND TROOP DOESN'T CHANGE

  • WHEN PROTEINS ARE PLACED IN THE

  • CELL.

  • I HAVE TO CONCLUDE FROM THIS

  • THAT THERE'S A CLAMP THAT LOCKS

  • THE EXOCYTOSIS PROCESS AND

  • BLOCKS ABOUT 50 -- BLOCKS IT

  • PROBABLY ABOUT A MILLISECOND OR

  • LESS BEFORE THE RELEASE PROCESS.

  • WHAT IS THAT CLAMP?

  • OVER A TEN YEAR PERIOD WE TRIED

  • TO FIND OUT WHAT THAT CLAMP WAS.

  • IN ABOUT 2005 WE DISCOVERED WHAT

  • IT WAS.

  • WAS A PROTEIN DISCOVERED BY TOM

  • PSEUDOOFT CALLED COMPLEXIN, AS

  • THE NAME SUGGESTS IT'S A COMPLEX

  • PROTEIN.

  • SOMETIMES NAMES NEVER FALL EWE

  • EVEN IF TERRIBLE NAMES.

  • IT WAS COMPLEXIN BECAUSE IT

  • FORMED A COMPLEX WITH A SNARE

  • MENTION AND NOBODY ELSE KNEW

  • WHAT IT IS AT THE TIME IT WAS

  • NEEDED FOR SYNAPTIC

  • NEUROTRANSMITTER RELEASE, WE

  • WON'T HAVE TIME TO GO INTO THIS,

  • IT HAS POSITIVE ROLES AN

  • NEGATIVE ROLES, IT IS BOTH AN

  • ACTIVATOR AND INHIBITOR.

  • BUT MOST IMPORTANTLY I WOULD

  • LIKE TO CONCENTRATE ON ITS ROLE

  • AS CLAMP OR INHIBITOR.

  • WHICH WE FOUND WHEN WE ADDEDDED

  • COMPLEXIN AS A CANDIDATE CLAMP

  • TO FUSION SYSTEMS THAT CONTAIN

  • DEFINED VAMP SYNTAXIN SNAP 25,

  • THAT OTHERWISE FUSED.

  • IF YOU ADD COMPLEXIN AT HIGH

  • ENOUGH CONCENTRATION THEY DIDN'T

  • FUSE.

  • WITH THAT THAT MEAN?

  • NOT NECESSARILY ANYTHING BUT IF

  • WE ADD CALCIUM SENSOR BACK AND

  • ONLY THEN IF WE ADD CALCIUM

  • COULD WE RESTORE FUSION IN THIS

  • ARTIFICIAL SYSTEM.

  • THAT SUGGESTED THATN%" PLEXIN COULD

  • BE THE CLAMP.

  • TOM PSEUDOOFF AND OTHERS SINCE

  • HAVE MUCH MOVE PHYSIOLOGICAL

  • EMPERIMENTS THAT SHOW THIS

  • BEYOND A DOUBT AND I'LL SHOW YOU

  • A COUPLE SUCH EXPERIMENTS TODAY.

  • TOM AND JOSEPH SOLVED THE X-RAY

  • LISTAL STRUCTURE OF COMPLEXIN IN

  • THE EARLY 2000s, THE HELICAL

  • PROTEIN THEY ARE PROBABLY THE

  • ONE THING YOU NEED TO KNOW ABOUT

  • IN THIS ENTIRE FIELD.

  • IN VESICAL TRAFFICKING IT'S

  • MOSTLY ABOUT HELICES INCLUDING

  • TETHER PROTEINS.

  • COMPLEXIN BINDS TO THE OUTSIDE

  • OF THIS HELIC BUN L AND THE

  • MEMBRANE PROXIMAL HALF.

  • IMPORTANTLY THIS IS THE

  • STRUCTURE OF COMPLEXIN WHEN IT

  • IS BOUND TO THE FULLY ASSEMBLED

  • COMPLEX WHICH ONLY OCCURS AFTER

  • FUSION IT DOES NOT NECESSARILY

  • INFORM US THEREFORE ABOUT THE

  • ROLE THAT COMPLEXIN PLAYS DURING

  • THE FUSION PROCESS.

  • WHERE IT ACTS AS A CLAMP.

  • WE ADDED COMPLEXIN TO THE

  • SURFACE FORCE APPARATUS

  • EXPERIMENT, A PIVOTAL EXPERIMENT

  • HERE, FRED PALSA AND I AND HIS

  • LABORATORY IN PARIS,

  • (INDISCERNIBLE) WE FOUND

  • COMPLEXIN CREATE AS NEW STATE

  • WHICH THE SNARE COMPLEXES FROZEN

  • IN THE HALF ZIPPERED STATE, 50%

  • AS BEST WE CAN.

  • SO WE KNEW IT DID SOMETHING

  • IMPORTANT AND IT SOMEHOW COULD

  • BE THE CLAMP.

  • SO THE NEXT QUESTION WAS HOW

  • DOES COMPLEXIN CLAMP?

  • AS I WARNED YOU, I'M GOING TO

  • ILLUSTRATE THIS BY A MODEL AND

  • THEN SHOW YOU THE X-RAY CRYSTAL

  • WORK IN THE CONTROLS, THAT STAND

  • BEHIND IT.

  • OUR PRESENT UNDERSTANDING ARE

  • REACHED BY KAREN RYANSH AN X-RAY

  • CRYSTALOGRAPHER DEPARTMENT OF

  • YALE IN MY LABORATORY SHOWN

  • HERE.

  • THIS IS THE HALF ASSEMBLED SNARE

  • COMPLEX WHERE THE INTERVENTION

  • BY COMPLEXIN WE BELIEVE BEGINS.

  • THE COMPLEXIN HELIX ACTUAL HI

  • HAS TWO PARTS.

  • THE CENTRAL HELIX AND THE

  • ACCESSORY HELIC.

  • THE CENTRAL HELIX IS ENDOWED

  • WITH THE ABILITY TO BIND VAMP

  • AND SYNTAXIN AND BINDS TO THE

  • ASSEMBLED SNARE PIN.

  • IN FACT, IT BINDS TO PORTIONS

  • THAT ARE PRESENT BUT ONLY

  • PRESENT WHEN THE SNARE COMPLEX

  • IS HALF ZIPPERED.

  • SO BEFORE THIS STATE, THERE'S NO

  • BINDING BY COMPLEXIN.

  • WHEN VN AS WE CALL IT IS HALF

  • ZIPPERED TO THE IONIC LAYER THAT

  • I MENTIONED, THEN THE BINDING

  • SITE IS CREATED FOR THE CENTRAL

  • HELIX.

  • WHEN THAT HAPPENS, THE COMPLEXIN

  • BINDS.

  • IT BINDS IN SUCH A WAY TO LEAVE

  • THE ACCESSORY HELIX POINTING

  • OUT.

  • THE CENTRAL HELIC BINDING TO THE

  • SNARE COMPLEX IS VERY IMPORTANT.

  • BECAUSE IT MEANS THAT YOU WILL

  • ALWAYS HAVE A COMPLEXIN THERE.

  • BY THE WAY, REMEMBER I MENTIONED

  • THAT THIS INITIAL BINDING OF VN

  • TO THE T SNARE IS VERY, VERY

  • SLOW.

  • ONE OF THE FACTORS THAT

  • DRASTICALLY ACCELERATES IT IS

  • THE ACCESSORY HELIC.

  • SO THIS DESIGN ENSURES THAT THE

  • ACCESSORY HELIC THE COMPLEXIN

  • THE LOADED AT THE TIME THE

  • VESICAL FIRMLY DOCKS.

  • SO YOU ARE POSITIONING YOUR

  • CLAMP IN ORDER TO MAKE SURE

  • PRE-POSITIONING TO MAKE SURE

  • IT'S THERE AT THE RIGHT TIME.

  • THE ACCESSORY HELIX IN FACT WILL

  • BE DOING THE CLAMPING.

  • IF OUTTAKE IT OFF, SOME

  • EXAMPLES, YOU DON'T GET

  • CLAMPING.

  • IF YOU MUTATE YOU DON'T GET

  • CLAMPING.

  • YOU NEED ACCESSORY HELIX FOR

  • CLAMPING.

  • YOU ONLY NEED THE CENTRAL HELIX

  • FOR THE ACTIVATION OF

  • NEUROTRANSMITTER RELEASE.

  • THE NEXT THING THAT HAPPENS IS

  • THAT THE ACCESSORY HELIX DOES

  • ITS JOB BY REACHING ACROSS AND

  • GRABBING A SECOND SNARE PIN.

  • SO IT CLAMPS IN TRANS.

  • IN THIS WAY ONE SNARE PIN THAT'S

  • ASSEMBLED CLAMPS ANOTHER,

  • MUTUALLY INHIBITING EACH OTHER.

  • LET'S LOOK AT THIS FROM THE TOP

  • VIEW IN WHICH WE NOW LOOK AT THE

  • PROTEINS LYING LIKE A SANDWICH

  • BETWEEN THE PLASMA MEMBRANE

  • BELOW AND SYNAPTIC VESICLE

  • ABOVE.

  • THE FIRST THING THAT HAPPENS IS

  • COMPLEXIN BIND BY CENTRAL HELIX.

  • LEAVING ACCESSORY HELICES FREE

  • TO BEHIND BETWEEN COMPLEXES.

  • THE SEQUENCE OF THE ACCESSORY

  • HELIX IS HOMOLOGOUS TO THE

  • SEQUENCE OF THE V SNARE IN THE

  • SAME REGION.

  • WHICH IS VERY ELEGANT.

  • 'S AN HONNARY V SNARE.

  • IT GOES RIGHT IN HERE AND BINDS

  • THE T SNARE A IF IT WERE A V

  • SNARE BUT P IT'S NOT.

  • BY BINDING THERE ITW

  • V SNARE FROM FURTHER ASSEMBLING.

  • THAT UNFOLDED PORTION OF THE V

  • SNARE CANNOT CONVERT TO A COIL

  • BECAUSE TO DO SO IT NEEDS TO

  • DISPLACE THE COMPLEXICSN.

  • SO THERE'S A TUG OF CAR

  • RESULTING IN CLAMPING SO IF THE

  • ACCESSORY COMPLEXIN HELIX IS

  • REMOVED AS ILLUSTRATED HERE THE

  • BLOCK ZIPPERING IS REMOVED AND

  • FUSION WILL PROCEED.

  • BUT THAT DOESN'T OCCUR BECAUSE

  • THE ACCESSORY HELIX IS CLAMPING,

  • THIS CLAMPING OCCURRING BETWEEN

  • TWO SNARE PINS.

  • AS YOU CAN IMAGINE THIS

  • ACCESSORY HELIX, THERE'S NOTHING

  • TO PREVENT IT FROM FORMING, FROM

  • RECRUITING ANOTHER SNARE PIN.

  • AND ANOTHER ONE TO GIVE RISE TO

  • WHETHER WE CALL A ZIG ZAG ARRAY

  • OF -- WHICH IS A HIGHLY

  • COOPERATIVE STRUCTURE AND THAT

  • GIVES RISE WE BELIEVE TO SIN

  • CHRONICITY.

  • ACCORDING FADING A LARGE NUMBER

  • OF SNARES IN ONE STRUCTURE THAT

  • IS ALL OR NONE T HAS THE ALL OR

  • NONE QUALITY OF COOPERATIVE

  • STRUCTURE, IT ALL WILL COME

  • APART AT ONCE, THERE'S A CLEAR

  • PREDICTION FROM THE STRUCTURE

  • AND THIS WILL LEAD TO THE

  • SYNCHRONOUS RELEASE OF A

  • VESICLE.

  • SO WE THINK THAT ULTIMATELY IS

  • WHAT SIN CHRONICITY COMES FROM.

  • THIS IS HOW WE REGARD CLASPING

  • TO OCCUR.

  • HOW DOES ACTIVATION éñ OCCUR?

  • NOW WHAT WE HAVE GOTTEN TO IS A

  • CLAMPED VESICAL THAT NEEDS TO BE

  • RELEASED WHEN CALCIUM ENTERS.

  • CALCIUM WHEN CALCIUM ENTERS THE

  • SENSOR FOR CALCIUM IS THE

  • PROTEIN SYNAPTIC TAGUMEN

  • DISCOVER AS A VESICAL COMPONENT

  • BY TOM SUDHOFF.

  • IN YEARS OF PAINSTAKING WORK

  • MUCH CONTROVERSIAL BUT NOW WIDE

  • UNDERSTOOD TO BE CORRECT TOM

  • WENT TO SHOW IT IS INTACT THE

  • CALCIUM SENSOR FOR SYNCHRONOUS

  • NEUROTRANSMITTER RELEASE.

  • AND PROBABLY THE MOST PERSUASIVE

  • EXPERIMENT IS A STRUCTURE

  • ACTIVITY EMPERIMENT WHERE HE

  • MUTATED THE CALCIUM BINDING

  • SITES IN SYNAPTOTAGMIN TO

  • RATCHET CALCIUM BINDING UP OR

  • DOWN IN TERMS OF BINDING

  • CONSTANT, PUT IT INTO A MOUSE IN

  • PLACE OF NORMAL SYNAPTOTAGMIN

  • GENE AND RATCHET UPPER DOWN

  • SENSITIVITY AT SYNAPSES

  • ACCORDINGLY.

  • SO THAT DOESN'T TELL US HOW

  • CALCIUM FUSION OCCURS BUT IT

  • TELLS US IT DOES OCCUR BY MEANS

  • OF THIS MOLECULE.

  • SO HOW DOES SYNAPTIC --

  • SYNAPTOTAGMIN SENSE CALCIUM?

  • I'M MOVING FROM WHAT I REGARD AS

  • FACT TO SPECULATION.

  • ONE THING THAT IS A FACT, THOUGH

  • IS SYNAPTOTAGMIN IS A TIGHT

  • BINDER OF MEMBRANES, IT HAS AN

  • ALOETHATIC LOOP THAT INSERTS TO

  • THE BILAYER AND INSERTS WHEN

  • CALCIUM IS BOUND AT THE BINDING

  • SITES.

  • THE CALCIUM BINDING SITE

  • CONSISTS OF A COMPOUND ASPAR

  • TICK ACID RESIDUES.

  • THERE ARE APARTIC ACID RESIDUES

  • THAT BIND CALCIUM IONS AN

  • COORDINATE IT WITH PIP-2 THAT IS

  • ON THE MEMBRANE.

  • SO THE ACTUAL CALCIUM BINDING

  • SITE IS A SANDWICH OF CALCIUM

  • BETWEEN THE TWO SITES.

  • NOW, THE COST OF DOING BUSINESS

  • FOR THATCAL YUM BINDING SITE IS

  • THIS ALOEPHATIC LOOP WHICH MUST

  • BE INSERTED BECAUSE IT'S THE

  • ONLY WAY THE CALCIUM BINDING

  • SITE CAN BE SATISFIED.

  • SO SYNAPTOTAGMIN INSERTS.

  • MUTATIONS IN SYNAPTOTAGMIN THAT

  • ABROGATE THE INSERTION OR

  • LIKEWISE DON'T ACTIVATE SYNAPTIC

  • TRANSMISSION.

  • ONE OR ANOTHER WAY EVERY MODEL

  • HAS TO ACCOMMODATE THIS AS AN

  • IMPORTANT ELEMENT OF SYNAPTIC

  • TRANSMISSION.

  • THE OTHER THING SYNAPTOT

  • ACTIONGMIN DOES IN LARGE STUDIES

  • IS PERTURB MEMBRANES IN ONE OR

  • ANOTHER WAY.

  • THE INITIAL EVIDENCE FROM HARVEY

  • MCMAHAN, TAGMIM IS ADDED IN

  • EXCESS TO LIPSOMES IT WILL TUBE

  • LATE THEM IN THE PRESENCE OF

  • CALCIUM.

  • THAT REQUIRES INSERTION OF THIS

  • REGION.

  • PROBABLY LESS THAN MEGA DOSES IT

  • DOESN'T TUBE LATE BUT

  • PHYSIOLOGICALLY PERTURBS IT AND

  • EVERY LAB WHO STUDIES THIS HAS

  • FOUND SYNAPTOTAGMIM ACCELERATES

  • THE RATE OF LIPSOME FUSION WHEN

  • YOU HAVE SNARES DRIVING IT IN A

  • CALCIUM DEPENDENT WAY.

  • IT DOESN'T FUSE BY ITSELF BUT

  • WILL ACCELERATE PROBABLY A

  • FACTOR OF 10 TO 100.

  • BUT VERY SUBSTANTIALLY THE RATE

  • OF LIPID FUSION, LIPID MEMBRANE

  • FUSION.

  • WE DON'T UNDERSTAND EXACTLY HOW

  • THAT WORKS, PROBABLY IT'S BEEN

  • CHANGING MEMBRANE INTENTION

  • ACCORDING TO BRUNGER AND OTHERS

  • BUT IT'S AN IMPORTANT FACT.

  • SO IT'S A CALCIUM SENSOR AND

  • AXEL RANT.

  • HOW DOES SYNAPTOTAGMIN FIT TYPE

  • THIS STORY?

  • THIS IS THE CUTTING EDGE OF THE

  • FIELD.

  • BUT WE KIND OF KNOW HOW

  • SYNAPTOTAGMIN BINDS TO THE SNARE

  • COMPLEX.

  • WE KNOW THIS LARGELY FROM THE

  • WORK OF ALEX BRUNGER, I'LL SHOW

  • YOU MORE DETAILS.

  • WHEN IT BINDS IT BINDS ONE PER

  • SNARE PIN AND WE IMAGINE IT

  • BINDS CALCIUM FROM THIS ARRAY

  • BOUND SYNAPTOTAGMIN.

  • WHEN IT BINDS CALCIUM IT INSERTS

  • TO THE BILAYER.

  • WE IMAGINE FURTHER THIS IS OUR

  • HYPOTHESIS, WHEN I'LL SHOW YOU

  • SIDE VIEW WHICH IS MORE

  • EXPLANATORY.

  • SO NOW YOU SEE THE SYNAPTOTAGMIN

  • BINDING.

  • WHEN CALCIUM ENTERS AND BINDS

  • TO SYNAPTOTAGMIN WILL CAUSE

  • REARRANGEN'T ONE WAYER ANOTHER

  • WHICH WE BELIEVE EXERTS

  • MECHANICAL FORCE ON THIS ARRAY

  • AND REMOVES A SNARE PIN THERE BY

  • UNCLAMPING.

  • THAT'S OUR MODEL, THE AMOUNT OF

  • EVIDENCE IS RELATIVELY MINIMAL.

  • AND BUT IT IS IN FACT A SIMPLE

  • POSSIBLY.

  • NOW, WHERE DOES THIS COME FROM?

  • I'LL TRUE TO BUZZ THROUGH THIS

  • MUCH MORE QUICKLY SEEING THE

  • HOUR.

  • WHAT KAREN AND I AND COLLEAGUE

  • ESPECIALLY DANIELLE CUMEL WHO

  • DID THE WORK HERE AND BRILLIANT

  • GUY IS TO SOLVE THE CRYSTAL

  • STRUCTURE OFR>Ñ4 SNARED COMPLEX.

  • FOR ALL REASONS I SHOWED YOU

  • WHEN VAMP IS HALF ZIPPERED

  • THAT'S WHEN WE THINK ALL THE

  • ACTION IS OCCURRING FOR

  • CLAMPING.

  • I EXPLAINED WHY THAT IS.

  • PROBLEM YOU HAVE IS YOU CAN'T

  • GET A CRYSTAL STRUCTURE OF A

  • DISORGANIZED STATE LIKE A FUSION

  • INTERMIT OR HALF ASSEMBLED SNARE

  • COMPLEX.

  • THE NEXT BEST THING YOU CAN DO

  • WHICH IS WHAT WE DID IS PRODUCE

  • A STABLE HALF ZIPPERED SNARE

  • COMPLEX BY USING JUST THE END

  • TERMINAL PORTION OF VAMP AN

  • LEAVING THE REST OUT.

  • SO THAT PRODUCES A STRUCTURAL

  • KNEW METIC OF HALF ZIPPERED

  • SNARE COMPLEX.

  • WE WERE ABLE TO CRYSTALLIZE THAT

  • IN COMPLEX WITH COMPLEXIN, NOT

  • SYNAPTOTAGMIN.

  • NO ONE GOT ONE TO MY KNOWLEDGE.

  • WE SOLVED THAT STRUCTURE.

  • AND WE GOT SOMETHING THAT WAS

  • MARKEDLY DIFFERENT FROM WHAT

  • SUDHOFF AN RIDDO FOUND.

  • THEY FOUND THAT COMPLEXIN LIES

  • AT ALPHA HELIX IN THE GROOVE

  • BETWEEN SYNTAXIN AND VAMP

  • CONTACTING BOTH OF THEM, THIS IS

  • THE SEN TRILLION HELIX PORTION,

  • ACCESSORY HELIX HAD NO CONTACTS

  • WITH THE SNARE COMPLEX BUT HELIX

  • RUNS PARALLEL TO THE SNARE

  • COMPLEX.

  • THAT'S NOT AT ALL WHAT WE FOUND.

  • WE FOUND THE OPEN CONFIRMATION.

  • IN CONTRAST TO THE OTHER

  • CONFIRMATION POST FUSION

  • REPRESENTING THE FULLY ZIPPERED

  • SNARE COMPLEX WE CALL CLOSED.

  • OPEN GOES OFF AS 45-DEGREES.

  • THE COMPLEXIN HELIX IS ISOMORE

  • FIXED.

  • 'S THE SAME HERE AND HERE EXCEPT

  • FOR THE WAY IT LIES ON THE SNARE

  • COMPLEX, IT'S BASICALLY THE

  • SAME.

  • BUT NOW GOES OFF AT 45-DEGREES.

  • THAT POSED A PROBLEM FOR US

  • BECAUSE I WAS TELLING YOU THE --

  • ALL THE GENETICS SAID THE

  • ACCESSORY HELIC DOES CLAMPING.

  • BUT WHAT'S CLAMPED IS THE

  • ASSEMBLING OF MEMBRANE PROXIMAL

  • WOULD BE HERE, PORTION OF THE

  • SNARE COMPLEX ASSEMBLED LAST,

  • HOW CAN THIS HELP -- HOW CAN

  • THIS INTERFERE WITH ZIPPERING OF

  • THIS WHEN THEY'RE ACTUALLY

  • DIVERGING AWAY FROM EACH OTHER.

  • THE ANSWER COMES FROM THE

  • CRYSTAL PACKING.

  • WHEN WE LOOK AT LAYER OF CRYSTAL

  • WE SEE A SNARE PIN, THE MEMBRANE

  • ANCHORS WOULD BE AT THIS END,

  • THE SYNAPTIC VESICAL WOULD BE

  • ABOVE AS IN THE CARTOON, THE

  • PLASMA MEMBRANE IN THE PLAIN

  • BELOW, HERE IS THE HALF ZIPPERED

  • VAMP.

  • NOW WHAT YOU SEE THE COMPLEXIN

  • CENTRAL HELIX LAUNCHING AN

  • ACCESSORY HELIX, BUT THAT

  • ACCESSORY HELIX IN THE OPEN

  • CONFIRMATION ACTUALLY BINDS IN

  • THE SAME GROOVE THIS V SNARE

  • WOULD IF IT CONTINUES TO ZIPPER.

  • EXACTLY AS I CARTOONED IT.

  • THIS IS THE BASIS FOR THE ZIG

  • ZAG ARRAY AND IDEA OF

  • INTERMOLECULAR CLAMPING AS THE

  • PRINCIPLE FOR CLAMPING OF

  • SYNAPTIC TRANSMISSION TO ALLOW

  • SIN CHRONICITY.

  • ANY CRYSTALOGRAPHER TELLS YOU

  • THIS IS GOOD BUT HOW DO YOU KNOW

  • THIS ISN'T A CRYSTALZATION OAR

  • FACT?

  • I HAD NEVER HEARD OF A

  • COUNTRYALZATION ARTIFACT.

  • -- CRYSTALZATION ARTIFACT.

  • I THOUGHT AS SOON AS YOU GET A

  • CRYSTAL STRUCTURE EVERYBODY

  • CONGRATULATES YOU.

  • PUBLISHES YOUR PAPER.

  • NO, THEY SEND YOU BACK HOME

  • THAT'S WHERE WE BIOCHEMISTS

  • START COMING IN TO THE PICTURE

  • BECAUSE HOW DO WE KNOW THIS

  • DIDN'T OCCUR AS A RESULT OF THE

  • CRYSTALLIZATION?

  • WE KNOW.

  • HOW?

  • BECAUSE WE CAN ISOLATE COMPLEXES

  • IN SOLUTION AND WE OBSERVE TO

  • BEGIN WITH THIS OPEN

  • CONFIRMATION EXISTS.

  • THIS WAS WORK BY CRYSTAL KUMAR

  • AND DANIEL RADOFF IN MY LAB.

  • NO DETAILS GIVEN THE TIME.

  • WE USE FRET ENTER INTERMOLECULAR

  • FRET.

  • WE FORM COMPLEXES OF COMPLEXIN

  • AND THE SNARE COMPLEX.

  • AND PUT A THREAT ACCEPTTOR ON

  • SNAP 25 ON THE BASE OF THE

  • COMPLEX AND TWO POSITIONS O

  • MORE.

  • IN THE COMPLEXIN ACCESSORY

  • HELIX, WE PLACE THE COGNATE

  • FLUORESCENT PROBE.

  • THIS ALLOWS US TO READ THE

  • DISTANCE THROUGH FRET, THE

  • SIGNAL WILL GO UP IN THE CLOSE

  • CONFIRMATION ON OPEN

  • CONFIRMATION.

  • AS YOU CAN SEE WE OBSERVE VERY

  • STRONG FRET SIGNAL WHEN WE HAVE

  • THE FULL LENGTH VAMP HERE BUT

  • WHEN WE HAVE THE FIRST 60

  • RESIDUES OF VAMP THE HALF

  • ZIPPERED STATE NOW WE GET OPEN.

  • I HOPE THAT'S

  • HOW DO WE KNOW THESE

  • CONFIRMATIONS ARE WHEY THEY SAY?

  • WE CAN TAKE THE FRET NUMBERS AN

  • CRUNCH THE NUMBERS.

  • AND ACTUALLY WE PREDICT WITHIN

  • 10% SYSTEMATIC THE CRYSTAL

  • COORDINATES OF THESE -- THIS

  • POSITION, THIS POSITION, THIS

  • POSITION AND THAT POSITION

  • RELATIVE TO THAT POSITION IN THE

  • TWO CRYSTALS TWO TYPES OF

  • CRYSTALS OPEN AN CLOSE IN THREE

  • FORMS.

  • SO WE'RE VERY CONFIDENT THAT

  • THIS IS THE NATURAL STATE AND

  • SOLUTION, THEREFORE THE

  • CRYSTALZATION DID NOT CAUSE THE

  • OPEN STATE, THE OPEN STATE HAD

  • TO BE ACCOMMODATE MISDEMEANOR

  • THE CRYSTAL.

  • THE OTHER POTENTIAL CONCERN IS

  • HOW DO WE KNOW THIS

  • TRANSINTERACTION BETWEEN THE

  • ACCESSORY HELIX AND T SNARE AT V

  • SNARE BINDING SITE OCCURS

  • INDEPENDENT OF CRYSTAL?

  • WE KNOW THAT BECAUSE WE CAN

  • MEASURE IN SOLUTION NOW THAT WE

  • KNOW TO LOOK FOR IT.

  • AGAIN, THIS IS PUBLISHED IN

  • 2011, IN NATURE STRUCTURAL

  • MOLECULAR BIOLOGY, I NEED TO

  • UPDATE THE SLIDE.

  • IF YOU MIX COMPLEXIN AND P THE

  • SNARE COMPLEX WITH A HALF ZIPPER

  • ED SNARE EXACTLY WHAT WENT

  • INTO THE CRYSTAL BUT WITH ITS

  • COMPLEXIN ACCESSORY HELIX SITE

  • PRE-BOUND AN PRE-BLOCKED BY

  • CENTRAL HELIX, I MEANT CENTRAL

  • HELIX BINDING SITE PRE-BLOCKED

  • SO ONLY THE HYPOTHETICAL

  • TRANSSITE INVOLVING THE TERMINAL

  • T SNARE IS AVAILABLE.

  • WE GET STOIC METRIC BINDING.

  • 15 MICROMOLAR BINDING CONSTANT,

  • NKT BINDING ENERGY, A NUMBER

  • WORTH REMEMBERING.

  • THAT IS CLOSELY LINKED TO THE

  • ACTIVATION FOR MEMBRANE FUSION.

  • NOW VERY IMPORTANTLY, WE MADE

  • MUTATIONS -- I CAN SEW -- WE

  • MADE MUTATIONS IN ACCESSORY

  • HELIX INCREASE OR DECREASE THE

  • BINDING ENERGY HERE.

  • YOU CAN SEE HERE POINT MUTATION

  • IN THE ACCESSORY HELIX RIGHT

  • HERE THAT ELIMINATES BEHINDING

  • >> SO WHAT DO WE PREDICT?

  • NORMAL GENE THIS GENE TESTED

  • PHYSIOLOGICALLY SHOULD CLAMP

  • BETTER THAN NORMAL AND SHOULD

  • REDUCE SPONTANEOUS FUSION THIS

  • IS WHAT WE SEE IN A CONTROL

  • ANIMAL, WHAT THEY SEE REALLY, IT

  • OCCURS T A COUPLE PER SECOND

  • MORE OR LESS AS DESCRIBED.

  • IF YOU KNOCK OUT COMPLEXIN THE

  • RATE IS UP TO PREVENT

  • SPONTANEOUS RELEASE.

  • A CLAMP P IF YOU REMOVE IT IF

  • YOU REMOVE THE CLAP THAT

  • PREVENTS THE SPONTANEOUS

  • RELEASE, WHAT HAPPENS TO

  • SPONTANEOUS RELEASE?

  • GOES UP.

  • THAT'S EXACTLY WHAT HAPPENS

  • HERE.

  • COMPLEX,N IS THE CLAMP.

  • IF WE MUTATE RESIDUES THAT FACE

  • THE INSIDE CONTACTING REGIONS

  • FOR THE T SNARE, WHEN WE DO

  • THAT, THEN OR IF WE DISRUPT THE

  • HELIX NOW ACTUALLY -- WE PUT IN

  • THE HUMAN COMPLEXIN WE ACTUALLY

  • HAVE NO AFFECT.

  • EVEN THOUGH IT'S THERE, IT'S

  • THERE AT THE SYNAPSE, IT DOESN'T

  • CLAMP.

  • IT CLAMPS NOT QUITE AS WELL.

  • WE'RE TRYING TO UNDERSTAND THIS

  • AS DROSOPHILA GENE IF WE PUT IN

  • ACCESSORY HELIX MUTANT THAT HAS

  • A FIVE TIMES HIGHER BEHINDING

  • ENERGY WE GET FIVE TIMES LOWER

  • SPONTANEOUS RELEASE.

  • SO TO SUMMARIZE THEN, THIS

  • INTERACTION IN THE CRYSTAL

  • STRUCTURE THAT WE BELIEVE IS THE

  • STRUCTURAL BASIS OF CLAMPING,

  • THAT INTERACTION MUST BE

  • CONTROLLING SPONTANEOUS RELEASE

  • BECAUSE AS WE RATCHET UP AND

  • DOWN THAT INTERACTION BY THE

  • SAME LOGIC AS TOM SUDOFF

  • RATCHETING UP AND DOWN CALCIUM

  • BINDING THAT RATCHETS UP AND

  • DOWN SYNAPTIC NEUROTRANSMITTER

  • RELEASE, THAT'S WHY IT'S THE

  • CALCIUM SENSOR.

  • THIS MUST BE THE CLAMPING

  • INTERACTION IF WE RATCHET UP AND

  • DOWN CLAMPING GETS RATCHETED UP

  • AND DOWN IN PHYSIOLOGICAL

  • SYSTEM.

  • SO THERE'S NO DOUBT THIS

  • TRANSINTERACTION THAT GIVES RISE

  • TO THIS ZIG ZAG ARRAY FROM THE

  • COUNTRYAL STRUCTURE IS THE

  • STRUCTURAL BASIS OF CLAMPING

  • WHICH MUST THEN OCCUR IN THE

  • HALF ZIPPERED STATE.

  • SO THIS IS A VERY IMPORTANT

  • EXPERIMENT I THINK FOR THE

  • ENTIRE CASE AND FOR THE ENTIRE

  • MODEL.

  • DO WE KNOW THAT THE ZIG ZAG

  • ARRAY EXISTS IN THE WAY IT DOES

  • IN THE CRYSTAL COURSE?

  • WE DOPE KNOW.

  • WE'RE INVESTIGATING.

  • IT MAYBE MORE TRUNCATED.

  • MAYBE INVOLVES TWO SNARE

  • COMPLEXES.

  • I DON'T KNOW AT THIS POINT.

  • BUT THAT INVOLVES CLAMPING

  • INVOLVES TRANSINTERACTION SEEMS

  • CLEAR.

  • HIGH CONCENTRATION HERE AS THEY

  • ARE IN THE CRYSTAL.

  • IN FACT, WHEN WE CALCULATE

  • ESTIMATE WHAT IT'S LIKE IN THE

  • SPACE HERE IT'S ACTUALLY LOWER

  • THAN THE CRYSTAL THAN IN THE

  • SPACE.

  • WHERE YOU HAVE TWO CLOSELY

  • OPPOSED MEMBRANES SO IT'S LIKELY

  • THAT WE HAVEN'T PROVEN THIS

  • ARRAY IS SOME SIGNIFICANT EXTENT

  • PROBABLY 10, 15 COPIES OF THE

  • SNARE PIN WE'RE GUESSING.

  • A VERY IMPORTANT POINT A VERY

  • IMPORTANT POINT IS THAT THIS IS

  • THE PRE-FUSION STATE IN THE HALF

  • ZIPPERED STATE, THIS IS WHAT

  • EVERYBODY IMAGINES THE FUSION

  • PORE MUST LOOK LIKE, IT HAS TO

  • BE CIRCULAR, IF IT HAS MULTIPLE

  • SNARES THEY HAVE TO BE ARRANGED

  • WHETHER BY INTENT OR NECESSITY.

  • SO -- AND THE OPEN STATE HERE,

  • OF THE COMPLEXIN OCCURS MUST GO

  • THROUGH A TRANSITION THEN

  • BETWEEN OPEN AND CLOSE, THERE

  • MUST BE A TRANSITION TO START

  • AGAIN BETWEEN OPEN AND CLOSED

  • STATE OF COMPLEXIN BECAUSE THIS

  • IS WHAT WE GET WHEN IT'S IN THE

  • CLAMP STATE AND THIS IS WHAT WE

  • SEE OR WHAT IS SEEN IN THE POST

  • FUSION STATE.

  • SOMEWHERE IN THERE THERE IS A

  • SWITCH.

  • NEW YORK CITY I THINK YOU CAN

  • SEE IN ORDER FOR THIS VAMP TO

  • CONTINUE TO ZIPPER THAT

  • ACCESSORY HELIX HAS TO GET MOVED

  • OUT WAY.

  • THAT'S OBVIOUS.

  • BUT WHEN THAT OCCURS, THERE IS

  • NOTHING THEN WHEN THAT HAPPENS

  • THERE'S NOTHING TO PREINVENTORY

  • THIS ZIPPERING.

  • IF YOU WERE TO TAKE ALL THESE

  • OPEN STATES AN CONVERT TO

  • CLOSED, I THINK YOU CAN SEE THAT

  • THE ZIG ZAG ARRAY CAN NO LONGER

  • FORM.

  • THE ZIG ZAG ARRAY THE ONLY FORM

  • IF THE OPEN CONFIRMATION AND THE

  • CLOSED THE ACCESSORY HELIX IS

  • SATISFIED WITH ITS OWN SNARE

  • COMPLEX AND NO LONGER CAN

  • INTERACT WITH ANOTHER ONE.

  • SO THIS OPEN TO CLOSE SWITCH IS

  • CLEARLY THEN WHAT WILL BE

  • DRIVING THE ACTIVATION PROCESS.

  • I WON'T HAVE TIME TO GO INTO

  • THIS, IT'S IN OUR PAPERS IF

  • YOU'RE INTERESTED BUT IT TURNS

  • OUT FOLLOWING RESIDUE 60 IN

  • VAMP, THERE'S RESIDUE 1, THERE'S

  • 60, BETWEEN 60 AND 67 THERE ARE

  • TWO VERY SPECIAL TURNS OF THE

  • HELIX.

  • THAT CONTAIN THREE ASPAR TICK

  • ACID RESIDUES.

  • THOSE ACTUALLY FORM AN

  • INTERACTION WITH THE ACCESSORY

  • HELIX HERE.

  • THAT INTERACTION CANNOT OCCUR

  • WHEN THOSE TWO TURNS ARE NOT YET

  • FOLDED.

  • WHEN THOSE TURNS ARE FOLDED,

  • THEY THEN CREATE THE BINDING

  • SITE THAT IS DIFFERENT BETWEEN

  • THIS STRUCTURE AND THIS

  • STRUCTURE AND THEY PULL THE

  • COMPLEXIN ACCESSORY HELIX DOWN.

  • WHAT HAPPENS IN FACT WE THINK IS

  • THAT WHEN ANY ONE OF THESE

  • ACCESSORY HELICES FLUCTUATES OUT

  • LONG ENOUGH, THIS VAMP SAY THIS

  • ONE HERE ZIPPERS, WHEN IT

  • ZIPPERS TO HELICES THAT CREATES

  • A BINDING SITE, WITH COMPLEXIN,

  • COMPLEXIN IS SWITCHED FROM OPEN

  • TO CLOSED WHEN IT DOES THAT IT

  • RETRACTS FROM THIS GUY.

  • WHEN THIS RETRACTS THEN THAT

  • VAMP GETS ZIPPER AND PULLS DOWN

  • THIS GUY.

  • LIKE A HOUSE OF CARDS IT GOES

  • DOWN.

  • WE HAVE TESTED THAT MUTATING THE

  • APARTIC ACID RESIDUE AND WHEN WE

  • DO THAT YOU GET IN VAMP AND YOU

  • GET PERFECTLY GOOD FUSION IN AND

  • OF ITSELF BUT YOU LOSE AT LEAST

  • IN OUR IN VITRO SYSTEM THE

  • ABILITY TO ACTIVATE FROM

  • CALCIUM.

  • WE'RE TESTING THAT IN A

  • PHYSIOLOGICAL SYSTEM IN

  • NEUROMUSCULAR JUNCTION THAT'S

  • OUR CURRENT VIEW.

  • SO I JUST WANT TO LEAVE YOU THEN

  • WITH OUR HYPOTHESIS OF HOW

  • ACTIVATION MAY WORK WHICH IS

  • LARGELY BASED ON COMBINING WHAT

  • I HAVE SHOWN FROM OUR LAB AND

  • VERY ELEGANT WORK THAT AXEL

  • BRUNNER AN COLLEAGUE AT STANFORD

  • USING FRET EXTENSIVELY TO

  • MEASURE POSITIONING OF

  • SYNAPTOTAGMIN ON THE SNARE

  • COMPLEX.

  • IT'S MISSING A CRYSTAL STRUCTURE

  • BOUND TO A SNARE COMPLEX IN ANY

  • STATE OF ASSEMBLY.

  • EVEN HIGH RESOLUTION PICTURE.

  • IF ANYBODY HAS AMBITION IN THIS

  • FEEL THAT'S HELPFUL TO HAVE.

  • BUT BASED ON HIS MOLECULAR

  • DYNAMIC MODEL AND BIOCHEMICAL

  • DATA CONSISTENT WITH THIS, IT

  • APPEARS THAT SYNAPTOTAGMIN BINDS

  • TO THE SNAP 25 SIDE OF THE

  • ASSEMBLING SNARE PIN.

  • IT BINDS ONE PER SNARE PIN.

  • STOICHIOMETRY, ONE ACTIVATOR PER

  • SNARE PIN.

  • IT BINDS TO THE SNAP 25 FACE.

  • THERE ARE FOUR HELICES IN THE

  • BUNDLE, TWO ON ONE SIDE, TWO ON

  • THE OTHER.

  • TWO ON ONE SIDE ARE THE TWO FROM

  • SNAP 25.

  • THEY SEEM TO BIND THIS

  • SYNAPTOTAGMIN.

  • THE OTHER TWO IS WHERE THE PLANT

  • SIDE WHERE THE CLAMPING OCCURS,

  • THAT IS WHERE VAMP AND SYNTAXIN

  • ARE WHERE THE ACCESSORY HELIX.

  • THE CENTRAL HELIX TO ALL THE

  • ACTION THAT I HAVE JUST BEEN

  • SHOWING YOU IS OCCURRING ON THE

  • OPPOSITE SIDE OF THE SNARE

  • BUNDLE WHERE WHERE SYNAPTOTAGMIN

  • BINDS.

  • WHEN IT BINDS THIS WAY

  • CONVENIENTLY THIS IS SHOWN

  • FACING THE VESICAL MEN BRAIN IT

  • FACES THE MEMBRANE AND WE DONE

  • KNOW IF ANY (INDISCERNIBLE) SO

  • ALL THAT NEEDS TO OCCUR WHEN

  • CALCIUM ENTERS IS FOR THIS

  • SYNAPTOTAGMIN TO BE ORIENTED BY

  • THE MEMBRANE.

  • I HAVE SHOWN YOU ANYTHING

  • FRAMEWORK THAT GOT REMOVEDDED

  • FROM.

  • THE SIMPLEST MODEL CARRIES THIS

  • OUT WE FORMED WITH TWO

  • NANODISABLES WHICH ZIPPER TO A

  • LARGE DEGREE BUT CAN'T FUSE

  • BECAUSE OF CONSTRAINTS.

  • WE PUT SYNAPTOTAGMIN ON IT AND

  • WE HAVE DONE STOP FLOW MEASURING

  • ON A SCALE OF MILLISECONDS IN

  • FACT THE INSERTION OF THIS LOOP

  • OF SYNAPTOTAGMIN TRIGGERED BY

  • CALCIUM AND ASKED WHETHER IT

  • REMAINS BOUND TO THE SNARE

  • COMPLEX AS IT INSERTS.

  • BECAUSE IF SYNAPTOTAGMIN IS

  • GOING TO ACTIVATE BY PHYSICALLY

  • DOING WORK ON THE SNARE COMPLEX

  • REMOVING IT FROM THE PLAIN, IT'S

  • PLAINER ARRAY STRUCTURE CLEARLY

  • NEEDS TO HANG ON DURING THIS

  • INSERTION PROCESS AND THAT IS IN

  • FACT THE CASE.

  • HERE WE LOOK AT FLUORESCENCE

  • ORING INSESSION OF ALOETHATIC

  • LOOP BETWEEN A AND V DOMAIN AND

  • SNAP 25 WHICH BECOMES ABSOLUTELY

  • INVARIANT.

  • BY THE WAY ALSO FOR THOSE WHO

  • MAYBE AFICIONADOS THE A AND B

  • DOMAIN DON'T MOVE WITH RESPECT

  • TO EACH OTHER DURING THIS POWER

  • STRUGGLE SO THERE IS A POWER

  • STROKE WHICH SYNAPTOTAGMIN

  • INSERTS TO THE BILAYER SHOWN

  • GENETICALLY TO BE NEEDEDTOR

  • PASSAGE OF CALCIUM SIGNAL TO THE

  • SNARE.

  • IT'S PHYSICALLY BOUND TO THE

  • SNARE AND BASED ON THIS IN VITRO

  • WORK MAINLY THE ONLY TENABLE

  • MODEL BECAUSE THE

  • SYNAPTOCONFIRMATION A AND B

  • DON'T CHANGE THEIR DISTANCE, A

  • MECHANICAL FORCE IS EXERTED AND

  • WE CAN'T PROVE TODAY THAT THAT

  • MECHANICAL FORCE IS TRANSDUCED

  • INTO REMOVING THE ACCESSORY

  • HELIX FROM THE T SNARE BEHINDING

  • SITE THAT CAUSES THE INHIBITION

  • BUT OBVIOUSLY CAN SEE THAT

  • THAT'S A VERY TENABLE HYPOTHESIS

  • THAT'S THE ONE WE'RE FOCUSED ON.

  • IT'S GENERAL TECHILY AND

  • KINETICALLY.

  • THIS IS MY LAST SLIDE.

  • THE ACTIVATE ENERGY TO REMOVE A

  • SNARE PIN CAN REQUIRE BREAKING

  • TWO INTERACTIONS.

  • IT'S ENTERACTING WITH ONE SNARE

  • PIN AND IN DISARRAY WITH

  • ANOTHER.

  • THIS INTERACTION CAN BE BROKEN

  • BY SO FOR THIS INTERACTION THAT

  • WILL BREAK TO THIS ONE OR 10 KT

  • WILL BREAK THIS ONE.

  • IF YOU PULL OUT IF YOU HAVE A

  • FLUCTUATION IF YOU HAVE 10-KT

  • ONLY YOU GET FLUCTUATIONS HERE

  • OPT ORDER OF ABOUT TWO

  • MICROSECONDS ACCORDING TO SINGLE

  • MOLECULE TYPES OF CALCULATIONS.

  • DOWN HERE ACCORDING TO SOMEBODY

  • OR OTHER RELATIONSHIP WHICH MY

  • PHYSICIST COLLEAGUE IS TELLING

  • ME ABOUT AND WHICH I MIGHT ONCE

  • HAVE UNDERSTOOD.

  • SORRY TO BE BLAH SAY ABOUT THAT

  • BUT THE PHYSICISTS AGREE THE

  • FLUCTUATION OCCURS IN 2 TO 20

  • MICROSECONDS, NOT LONG ENOUGH TO

  • BE PERSISTENT.

  • SO THAT ALLOWS DETERMINED ACT

  • INVESTIGATION BY REMOVING TWO OF

  • THESE POINTS WHEN YOU REMOVE

  • TWO, WHEN YOU LOOK YOU'LL SEE

  • THE WHOLE THING FALLS APART LIKE

  • DOMINOES BUT IF YOU REMOVE IT

  • TAKES 20 KT TO CAUSE ACTIVATION.

  • THE SIMPLEST HYPOTHESIS IS THAT

  • THIS+ THE ACTUAL ENERGY RELEASED

  • WHEN IT BINDS CALLS YUM PLUS PIP

  • AT RELEVANT CONCENTRATION 45 KT.

  • IS IT FULLY AVAILABLE TO TO BE

  • CHANNELED?

  • NO, DID NOT KNOW THAT, WITH WE

  • DONE KNOW THAT BUT AT LEAST IT'S

  • ATENABLE HYPOTHESIS.

  • AND KINETICALLY TENABLE AS WELL.

  • SORRY FOR THE BREATHLESS FINISH.

  • I WOULD LIKE THE JUST THANK THE

  • COLLEAGUES WHO ARE MOST

  • CRITICALLY IMPORTANT FOR THIS

  • WORK, THE EXPERT CRYSTALOGRAPHY

  • DANIELLE KUMEL AND CAPE RYAN ISH

  • PROFESSOR IN YALE CELL BIOLOGY

  • DEPARTMENT, THE

  • ELECTROPHYSIOLOGY THAT WAS SO

  • IMPORTANT ESTABLISHING THE

  • PHYSIOLOGICAL RELEVANCE AT MIT.

  • AND WORK IN THE FIRST INSTANCE

  • COMPLEXIN CLAMPS IN A DIFFERENT

  • STATE THAT GIVES US THE CLUE HOW

  • TO DESIGN THE MOLECULE FOR THE

  • CRYSTAL STRUCTURE FOR THE

  • PHYSICIST,'S IMPORTANT IN ALL

  • COLLABORATIONS.

  • MORE RECENTLY THE OBSTACLE WORK

  • WITH ANOTHER PROFESSOR AT YALE

  • AND FOLKS FROM MY LAB I

  • MENTIONED I BELIEVE AS I HAVE

  • GONE THROUGH THE WORK IN THEIR

  • PARTICULAR CONTRIBUTION.

  • SO THANK YOU ALL VERY MUCH.

  • [APPLAUSE]

  • >> WE'LL TAKE QUESTIONS AFTER

  • THE CALL CLEARED OUT PEOPLE WHO

  • NEED TO GO RIGHT AWAY.

  • >> I ONLY HAPPY TO DO IT HERE OR

  • GO TO THE RECEPTION.

  • MAYBE HARDER TO DO THAT.

  • >> QUESTIONS.

  • >> THANK YOU.

  • VERY, VERY EXCITING AND ALSO IT

  • HAPPENS IN THE IMMUNOLOGICAL

  • EXCEPT FOR SLOWER PACE.

  • MY QUESTION AND MAYBE SUGGESTION

  • IS YOU MENTIONED THE END

  • TERMINUS IS ACTUALLY STARTING

  • THE WHOLE GAME FOR STRUCTURE OF

  • AND SIGNAL TO THE END TERMINAL.

  • IS THERE ANY INFORMATION KNOWN

  • ABOUT THE END TERMINAL

  • COMPOSITION FOR GROUP THAT IT'S

  • --

  • >> WHAT'S THE QUESTION THEN?

  • >> THE COMPOSITION OF THE END

  • TERMINAL AND THE C TERMINAL,

  • CHANGES AND THE CHARGE --

  • >> WE SHOULD DISCUSS PRIVATELY

  • BUT COMPOSITION OF THE AMINO

  • ACIDS ISN'T LIKELY TO CHANGE, IF

  • THAT'S WHAT YOU MEAN.

  • IS THERE ANOTHER QUESTION?

  • >> OKAY.

  • >> YES.

  • >> IT SEEMS LIKE ONE OF THE

  • CRITICAL THINGS IN THE

  • MEASUREMENT OF THE SYNCHRONOUS

  • PHENOMENA AND TIME DEPENDENT ARE

  • THE TOOLS THAT YOU USE AND X-RAY

  • COUNTRYALOGRAPHY ARE A SNAP SHOT

  • THAT HAPPENS OVER A PERIOD OF

  • TIME.

  • SOME SECONDS OR NANOSECONDS.

  • IF YOU HAD A WISH LIST OR -- OF

  • A NEW TOOL THAT YOU COULD USE OR

  • MAYBE IN EXISTENCE, WHAT DOES

  • THAT IT WILL LOOK LIKE?

  • TWEEZERS IS THERE ANYTHING KNOWN)/P

  • ABOUT THE LIPID ENVIRONMENT --

  • AND HOW THAT MIGHT ASSIST.

  • THISES WHO FUSION PROCESS?

  • >> GOOD QUESTION.

  • ASIDE FROM PIP IS A BEING ASIDE.

  • THAT IS ABSOLUTELY REQUIRED

  • PHYSIOLOGICALLY, REQUIRED IN

  • VITRO SYSTEMS FOR THE MAXIMUM

  • EFFECT, IT IS VERY,VERY

  • IMPORTANT.

  • OTHER THAN THAT WE'RE

  • UNFORTUNATELY LEFT WITH THE

  • IMAGINATION THE SNARES ARE

  • LARGELY UNCARING ABOUT THE SPEED

  • OF LIPIDS, IT WILL GO UP OR DOWN

  • BUT NOT DETERMINING.

  • THERE'S SOMETHING IMPORTANT IN

  • THE CLUSTERING THE T SNARES SEEM

  • TO BE IN MANY DIFFERENT CELLS IN

  • SO CALLED LIPID RAS OR DOMAINS

  • THAT ARE CHOLESTEROL DEPENDENT,

  • YOU DON'T KNOW ENOUGH ABOUT

  • THEM.

  • SO I DON'T WANT TO SAY -- I

  • ACTUALLY TO THINK THEY'RE QUITE

  • IMPORTANT, MAYBE THE (INAUDIBLE)

  • ITSELF IS A LIPID RAS. THERE'S

  • SUGGESTIONS ALONG THOSE LINES SO

  • THERE IS A VITAL IMPORTANCE BUT

  • THE -- NEITHER IN VITRO SYSTEMS

  • NOR THE CRUDE TOOLS AVAILABLE, I

  • DON'T MEAN TO SAY GENETIC IS

  • CRUDE BUT RELATIVE TO THE TYPE

  • OF PHYSIOLOGY THAT KNOCKING

  • SOMETHING OUT, IT'S ALL

  • RELATIVELY PROVEN SO WE DONE

  • KNOW.

  • I WILL LIKE TO KNOW.

  • >> DO YOU HAVE ANY INSIGHT TO

  • WHAT HAPPENS IN ASYNCHRONOUS

  • RELEASE WHICH MAYBE IMPORTANT

  • FOR INSULIN SECRETION IN

  • >> DOES NOT REQUIRE

  • SYNAPTOTAGMIN.

  • I DON'T HAVE PERSONAL KNOWLEDGE,

  • MY IMPRESSION FROM THE

  • LITERATURE IS THAT SYNAPTOTAGMIN

  • IS NOT THE CALCIUM SENSOR, MY

  • IMPRESSION IS THERE'S SOME

  • SENTIMENT THERE'S A RELATED

  • PROTEIN CALLED DOCK 2 THAT MAYBE

  • THE CALCIUM SENSOR BUT MY OTHER

  • IMPRESSION IS CONTROVERSIAL

  • THERE. IS A CALCIUM SENSOR.

  • THAT'S CLEAR.

  • >> WHAT IS COMPLEXIN DOING IN

  • THAT SITUATION?

  • >> I DON'T KNOW.

  • I WOULD PREDICT PROBABLY

  • NOTHING.

  • I WOULD GUESS IT'S NOT INVOLVED.

  • IN FACT, YOU CAN GET CALCIUM

  • DEPENDENT -- THE NICEST

  • EXPERIMENT HERE, THERE'S A LOT

  • OF NICE EXPERIMENTS BUT TO MY

  • MINE THE NICEST IS IN VITRO

  • EXPERIMENT WITH PURE PROTEINS BY

  • THOMAS SULNER LAST YEAR BECAUSE

  • IT -- EWE ABSOLUTE CONTROL OF

  • EVERYTHING.

  • WHAT HE SHOWS IS IF YOU LEAVE

  • COMPLEXIN OUT BUT YOU HAVE STILL

  • HAVE PIP 2 SYNAPTOTAGMIM AND

  • SNARES YOU GET VESICAL DOCKING

  • AND RELEASE THAT'S CALCIUM

  • DEPENDENT.

  • BUT THE AMOUNT OF FUSION IN THE

  • ABSENCE OF CALCIUM GOES UP VERY

  • DRAMATICALLY, THE AMOUNT OF

  • VESICAL FUSION THAT YOU GET WHEN

  • YOU ADD CALCIUM IS -- BRINGS YOU

  • UP TO 100% BUT LESS -- FAR TO GO

  • BECAUSE YOU FUSED 20%.

  • SO THERE'S LESS RELEASE IF YOU

  • WANT TO THINK ABOUT IT THAT WAY.

  • INSTEAD OF IT GETTING DONE LESS

  • THAN SECOND IT DRIBBLES OUT 10,

  • 20 SECONDS, NO FUSION IN THE

  • ABSENCE OF CALCIUM, TOTAL HI

  • CLAMPED.

  • 100% RELEASE AND ALL WITHIN THE

  • FIRST SECOND.

  • ASYNCHRONOUS GOES TO

  • SYNCHRONOUS.

  • ASYNCHRONOUS DEPENNING HOW IT

  • IS, YOU CAN GET THAT WITH

  • SYNAPTOTAGMICS N ALONE.

  • IT'S LIKELY AN IMPEDIMENT TO

  • MEMBRANE FUSION BY SITTING

  • BETWEEN THE TWO MEMBRANES.

  • SO IT SLOWS THE TERMINALS.

  • LET'S ADJOURN TO THE LIBRARY AND THANK YOU FOR COMING

>> HELLO.

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B2 中高級 美國腔

突觸處神經遞質同步釋放的分子機制 (The Molecular Mechanism of Synchronous Neurotransmitter Release at Synapses)

  • 285 12
    Precious Annie Liao 發佈於 2021 年 01 月 14 日
影片單字