Synaptic vesicle exocytosis

Question 1

Which keyproteins are involved in docking and priming?

Answer 1

RIM, RIM-BP, MUNC13, Rab3 and Ca^2+ channels

Question 2

Explain the mechanism of docking.

Answer 2

RIM binds to Rab3 (on vesicle) and Ca^2+ channels (on plasma membrane). Binding to Ca^2+ channels recruites the vesicles to the docking site, binding to Rab3 mediates vesicle binding

Question 3

Which protein is involved in Ca^2+ sensing?

Answer 3

Synaptotagmin-1

Question 4

Which proteins are involved in the fusion?

Answer 4

The SNARE (SNAP receptor) proteins: 2 T-SNAREs (in/on PM), syntaxin-1 and SNAP-25; 1 V SNARE (in VM), synaptobrevin

Question 5

Explain the mechanism of the fusion.

Answer 5

The SNAREs zipper up as 4-helix bundle from the cytosolic ends to the TM regions. Synaptotagmin-SNARE interactions induce the full zippering in Ca^2+ induced vesicle fusion, by conformational changes in Ca^2+ bound synaptobrevin

Question 6

Explain the actions of NSF and alfa-SNAP.

Answer 6

NSF is an ATPase, and alfa-SNAP is an adaptor protein binding to NSF. They are molecular chaperones, and the energy from ATP hydrolysis is used to disassemble the SNARE proteins AFTER fusion

Question 7

What are the difference between the “kiss-and-stay” and the “kiss-and-run” model?

Answer 7

Kiss-and-stay: local reuse, kiss-and-run: fast recycling without an endosomal intermediate

Question 8

Explain the clathrin-mediated endocytosis.

Answer 8

After NT emptying: clathrin-coated vesicles starts forming, and when big enough, it is seperated from the PM (scission) with the help of dynamin. Dynamin is a GTPase, that twist around the PM bound part of the endosome, contricting it. The vesicle are uncoated, and finally refilled with NT.

Question 9

What are botulinum- and tetanus toxin?

Answer 9

SNARE proteases, cleaving SNARE proteins at different sites.

Question 10

How does BoNT work?

Answer 10

Inhibits neurotransmitter release at neuromuscular junctions, causing paralysis

Question 11

How does TeNT work?

Answer 11

Inhibits inhibitory interneuron synapses of the spinal cord, causing cramps

Question 12

What does latrotoxin do, and where does it come from?

Answer 12

Forms Ca^2+ permeable pores in the presynaptic PM inducing exocytosis. Venom of black widow spider.

Question 13

Explain the mechanism of BoNT and TeNT.

Answer 13

HC domain bind to PM, HN domain is responsible for the membrane translocation and the N-terminal domain is a zinc-endopeptidase specifically cleaving SNAREs