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Molecular and Cellular Neuroscience > Molecular Mechanisms Of Exocytosis And Endocytosis > Flashcards

Molecular Mechanisms Of Exocytosis And Endocytosis Flashcards

1
Q

What protein binds a reserve vesicle to the microfilaments?

A

Synapsin

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2
Q

From proximal to distal on a neuron what are the different vesicle pools?

A

Reserve
Proximal
Docked

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3
Q

What is the distance between the reserve pool and the active zone?

A

200nm

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4
Q

What is the proximal pool embedded in?

A

Cytomatrix assembled at active zone (CAZ)

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5
Q

What channels are the docked pools closely associated with?

A

Voltage gated calcium channels

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6
Q

What regulates the interaction of reserve poor with synapsin?

A

CaMKII

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7
Q

What happens no gene KO of synapsin?

A

Decrease in amount of reserve vesicles

But no effect on proximal/ docked pool

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8
Q

What is the active zone?

A 
Essentially the pre synaptic equivalent of the PSD
friend from
- structural proteins (piccolo etc)
- SNARE proteins
- complexes involved in endocytosis
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9
Q

Name some important proteins within the active zone

A

CASK
Munc13-1
Piccolo and bassoon
RIM1(alpha)

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10
Q

What is CASK?

A

Member of the membrane associated guanylate kinase superfamily involved in membrane associated signal complex formation

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11
Q

What proteins does CASK interact with?

A

VGCC (may service to cluster calcium channels in active zone)
Cell adhesion molecules
Beta neurexin
Mint-1 via CamK domain

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12
Q

What does mint-1 interact with?

A

Munc-18 which is important for fusion of docked vesicles

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13
Q

What domains does munc13-1 have?

A 
C1 domain (binds DAG )
3xc2 binding domain (binds calcium)
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14
Q

Why is munc13-1 important?

A

Disruption decreases spontaneous and evoked NT release

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15
Q

What protein translocates munc13-1 to membrane?

A

Doc2(alpha)

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16
Q

What does munc13-1 do to munc-18?

A

Displaces it from syntaxin

Allowing core complex formation

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17
Q

What does RIM1 stand for ?

A

Rab3 Interacting molecule

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18
Q

What is RIM1 function?

A

Binds to rab3 in an GTP dependant manner
Translocates vesicle to proximal pool
Is a rab3a effector protein

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19
Q

Molecular weight of RIM1

A

180kDa

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20
Q

Molecular weight of piccalo?

A

530kDa

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21
Q

Molecular weight of Basson?

A

420Kda

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22
Q

Where are piccalo and basson found?

A

Cytomatrix assembled at active zone (CAZ)

23
Q

What is the function of piccalo and basson?

A

Synaptogenesis

Tethering of proteins

24
Q

How many domains do they have in common?

A

10 - the piccalo basson homology domains (PBH)

25
Q

What is the difference between piccalo and bassoon?

A

Piccalo has a pdz and 2xc2 domains at c terminus (missing in bassoon)

26
Q

Why are the piccalo zinc fingers important?

A

Bind to prenylated rab acceptor (PRA1) on vesicles

Since PRA1 can interact with V-SNARES it may be involed in endocytosis/exocytosis

27
Q

What do the proline rich sequences in piccalo and bassoon allow for?

A

Tether proteins to SH3 domains of protein involved in endocytosis

28
Q

What I the function of the vesicular ATPases?

A

Load NT along with H+ into 20nm vesicles

29
Q

How large is a v-ATPase?

A

1000kDa with 13 subunits

One per vesicle

30
Q

What are the stages of the vesicle cycle?

A 
NT storage into vesicle
Transition of active zone
Docking
Priming
Fusion
Endocytosis 
Endosome fusion
Budding 
(Repeat)
31
Q

Vesicular glutamate transporter transport glutamate into vesicles. How many subtypes are there?

A

3

32
Q

Vesicular glutamate transporter transport glutamate into vesicles. How many TMDS?

A

8-10

33
Q

Vesicular glutamate transporter transport glutamate into vesicles. How do they function?

A

ATP used to pump H+ into vesicle

Which creates an electrochemical gradient which drives glutamate entry (as negativity charged)

34
Q

Vesicular glutamate transporter transport glutamate into vesicles. What is the effect of chloride ions?

A

High chloride inhibits channel function

Low chloride stimulates channel function

35
Q

What occurs in the docking stage of exocytosis?

A

Vesicle in close proximity to membrane

36
Q

What happens in the priming stage?

A

T SNARE and V SNARE interaction (core Complex formation)

37
Q

What happens during fusion?

A

Membranes of vesicle and plasma membrane fuse to to opening of VGCC

38
Q

What is the core complex?

A

Tight 4 helix bundle which pulls vesicle towards the plasma membrane in stepwise zipping manner from distal SNARE end to proximal

39
Q

What does SNARE mean?

A

Soluble NSF attachment protein receptors

40
Q

What motifs mediate core complex formation?

A

70 aminoacid alpha helix motifs

Synaptobrevin = R motif
Syntaxin = Qa motif
SNAP-25 (synaptosome associated protein of 25kDa) = Qa and Qb

41
Q

What can inhibit SNARE complex formation?

A

Proteins which have similar SNARE formation motifs and compete for snare interaction such as amisyn

42
Q

Same the t and v SNARES

A

T snares = synaptotagmin and synaptobrevin
V snares = syntaxin and SNAP-25
Other proteins such as munc13-1 / 18 and Vap33 are important in exocytosis

43
Q

What is kiss and run?

A

Vesicles rapidly endocytose and recycle without clathrin mediated endocytosis
They do not remain in the active zone but undock and recycle locally and rapidly

44
Q

Describe the role of syntaxin and munc protein interaction

A

Munc18 binds to and inhibits syntaxin function
Munc13-1 then displaces munc-18 allowing syntaxin to bind to other proteins
Core complex formation which may occur with or without munc 13 bound to the amino terminus of syntaxin

45
Q

What domains of synaptotagmin bind calcium?

A

C2a (3 calcium) C2b (2 calcium)

46
Q

What happens when calcium binds to synaptotagmin?

A

Allows association of synaptotagmin with snap-25 and syntaxin
2A and 2B domains then insert into phospholipid membranes

47
Q

Is synaptotagmin a high affinity of low affinity calcium sensor?

A

Low affinity - causes synchronous release

48
Q

From the presynaptic calcium current to the post synaptic action potential how long does it take?

A

Approx 1ms

49
Q

What are the 4 mechanism of endocytosis?

A

Clarthin mediated endocytosis
Kiss and run
Kiss and stay
Bulk retrieval

50
Q

Why might 2 mechanism of endocytosis exist?

A

A high frequency stimulus will deplete vesicles and from membrane cisternae. Vesicles reappear at expense of cisternae (CME)

Low frequency stimulation vesicles recycle fast enough there is no depletion of vesicles (KISS AND RUN)

51
Q

What is clathrin mediated endocytosis?

A

Ap-2 binds to cargo patch in vesicle (?synaptotagmin) and recruit clathrin triskelions
Form clathrin coated pits
Dynamin needed to cleave vesicle from membrane

52
Q

What are some of the characteristics of CME?

A

Very slow - cannot be sole mechanism of endocytosis
Occurs are peripheral synaptic membrane
Can occur from deep membrane infolds

53
Q

In kiss and run does the vesicle collapse into the membrane?

A

No, forms transient connection in 5% of cases

Low probability of neurotransmitter release

54
Q

Bulk membrane retrieval describes….

A

Large area of membrane are internalised following complete vesicle fusion with membrane

Molecular and Cellular Neuroscience (11 decks)

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