Lecture 5.1 Flashcards
What is the synaptic unit
The active zone
What is in an active zone?
The pre synaptic region continuing many vesicles
Widened electron dense intercellular space
Post synaptic density (Type 1-excitatory have a thicker post synaptic density than type 2-inhibitory)
How many vesicles are released per action potential?
Each active zone releases one or so vesicles per AP
How many molecules of ACh are in one vesicle in the NMJ?
Around 10,000 molecules
Why is the mossy fibre synapse stronger?
More current flows to the dendrite
Synapses are close to the cell body therefore there is less current leakage-the full effect is felt
Name the 3 vesicle pools
Reserve Pool-where the majority of vesicles are kept
Recycling Pool
Readily Releasable Pool-Pre docked/roughly 10 vesicles
What tethers recycling and reserve vesicles?
Actin filaments
Which of the 3 vesicle types can be mobilised quickly?
Recycling Vesicles
What determines the probability of vesicle release?
The number of pre docked vesicles
The sensitivity of the release trigger to calcium
The amount of Ca entry
The site of Ca entry
Name 5 surface proteins of vesicles
Synaptotagmin, Synapsin, Rab 3, Rab 5, VAMP
What is Synaptotagmin?
Surface protein that is the Ca trigger
What is Synapsin?
A surface protein that tethers the resting vesicles to actin
Phosphorylation allows forward movement of vesicle
What is Rab 3?
A surface protein, that targets vesicles to the docking site by binding to RIM protein
What is Rab 5?
A surface protein, important for re-uptake after exocytosis of the vesicle
What is VAMP(Synaptobrevin)?
A surface protein, vesicular SNARE protein, formation of the docking complex requires a SNARE complex
VAMP interacts with vesicular amp 3 snare proteins, forms a helix which is the docking site
What do all membrane fusion events require and what do they do specifically?
Formation of a SNARE complex (pulls the 2 membranous structures together)
A SM protein ex./Munc 18(initiates phospholipid mixing)
What is required for vesicle docking?
Requires fusion of 4 SNARE protein alpha Helices (1 supplied by the vesicle, 3 supplied by plasma membrane at the synaptic terminal-2 Helices per Snap 25 protein, 1 helix per syntax in protein
What is synaptic failure?
Where a vesicle is not released at the synapse
Describe the molecular mechanisms that occur when a vesicle docks to the membrane?
Vesicle docks
SNARE complexes form to pull membrane together (Snaptobrevin, Syntaxin, 2 SNAP-25)
Entering Ca binds to Synaptotagmin
Ca bound Synaptotagmin catalysed membrane fusion by binding to SNAREs and plasma membrane
What 2 proteins promote membrane bending and what do they form complexes with?
Munc 13 and Munc 18
With Syntaxin
What is the main role of RIM and what does it bind to?
To bind key players
Binds to the vesicle, VACC and Munc 13
All vesicular fusions occur via ………complexes
SNARE complexes
Does vesicular fusion with in the cell require Ca?
No, only in the synapse is Ca needed
Why does synaptic vesicle fusion need Ca?
Phospholipid mixing and vesicle fusion does not occur in the absence of Ca
