-
Visualising nerve junctions
Make fluorescent derivative of NA with hot formaldehyde vapour
-
Describe SNAREs
- Synaptobrevin: v-SNARE, anchored in vesicle membrane by a hydrophobic carboxy terminus. central 70aa alpha-helix
- Syntaxin: t-SNARE
- SNAP 25: t-SNARE
- Core complex: 4 a-helices (1 each, 2 from SNAP 25)
- form a leucine zipper -> brings vesicle and plasma membranes close together
-
Botulinum toxin
- Cleaves target SNARE by peptidase activity
- Specific SNARE depends on which of 7 subtypes
- B, D, F, G: Synaptobrevin
- A, E: SNAP-25
- C1: Syntaxin and SNAP-25
- Insertion into cholinergic neurons: C-terminus of heavy chain binds nucleoside receptor eg GT1b, N terminus translocates light chain in through channel
- Botulinum anti-toxin only works within 30mins of adsorption of toxin
- Symptoms: somatic muscle weakness (inc resp), loss of cholinergic activity (constipation, blurred vision, dry skin, urinary retention), slowed heart rate (due to effects on NA nerves?)
-
Tetanus toxin
- Binds to synaptobrevin
- Retrogradely transported to cell body, then transferred to inhibitory interneuron - this cannot now release its transmitter, so the motor neuron becomes excitable
-
Synaptotagmin
- Calcium sensor
- N-terminal TM region in vesicle
- 2 low affinity Ca binding regions (homology to PKC)
- binds to phospholipids (inc syntaxin) in Ca dependent manner
-
Synapsins
- Non-phosphorylated: bound to vesicles and cytoskeleton
- Phosphorylated (by PKA and CaM kinase II): dissociate from vesicle: vesicle can translocate to active zone
|
|