Final Exam: Chapter 8 Flashcards
Once axons reach target…
form junctions and synapse
growth cone differentiates
postsynaptic neurons develops specialized site
Who makes decision to stop growth and differentiate?
Shared between pre/post synaptic neurons
intracellular signals are important
_______ important for postsynaptic clustering of Ach R at NMJ
presynaptic signals
postsynaptic slower to commit
As it matures, postsynaptic density
increases
Cells push away from each other to receive synaptic contacts. Do they do this because they get bigger?
no more dendrites, all connective features take up volume
Stages of synapse formation
1) Recognize signal
2) membrane glycoprotein
3) tight junctions
4) immature synapse
5) mature synapse: with ECM
What do growth cones release to find target?
Why does it do this?
NT, not always the final one through
helps cell realize partner, helps post synaptic cell initiate synaptic changes
Experiment: Growth cone in FM4-64 dye, depolarize to take FM into vesicles, depolarize again to release
vesicle proteins? in GC filopodia, early presynaptic machinery
ex: synatophycin (phicin)
Experiment: stimulate growth cone with myoball (ball of muscle cells) nearby
Result: longer left together, increase frequency and amplitude, lots of quick changes
muscle cell contact ENHANCES electrical transmission
Inject Ca2+ sensitive dye on GC and put them in contact with…
1) GC (nothing, it’s just the GC)
2) muscle cell
3) neuron
4) muscle cell, but in a Ca2+ free solution
1) resting Ca2+
2) increase ca2+
3/4) no rise
Growth cone + calcium ionophor
super permeable membrane, collapses, meets target
increase calcium = ___ GC
round Growth cone
Once contact between GC and muscle cell, calcium levels
rise
Netrin-1
chemoattractant, GC depolarized
Sema-3A
chemorepellent, GC hyperpolarized
Ca2+ flow in GC filopodia when ___ occurs.
influx Ca2+ = _____ polymerization
pre/post synaptic contact
actin polymerization
______ provides adhesion during synapse between GC and postsynaptic muscle
NCAM
What happens to NMJ synapses of drosophilia Fas2 mutants?
Retraction
Hippocampus uses ____ linking thing
Also forms ____ which allows presynaptic side to envelope them and hold it together.
Cadherins
Dendrite spines
Block cadherin, block…
synapse formation
CAMS and synapse formation: order it goes together
Actin- alpha catenin- beta catenin- cadherins
actin-Afadin-Nectin, which keeps is locked in
Presynaptic proteins: quick to the game
53 min: + Basoon labeling (presynaptic marker)
75 min: 90% contact complete active zones
What labels postsynaptic side?
PSD-95. Use that and bassoon for pre to see that presynaptic side is faster.
Intracellular signaling promotes differentiation: How to pre/post synaptic sides stabilize
Pre: Post
1) Neurexin: neuroligin
2) FGFR2: FGF
3) Frizzeled: Wnt
This results in stabilization
Postsynaptic has ligands
What happens to alpha-Btx after innervation?
now clustered at synapse
Is innervation required for alpha-btx clusters?
Experiment: HB9 -/- mice
No! still have alpha-btx stains .
Moral: Ach receptors tend to be around the right areas, even if not necessarily the perfect match up
alpha-btx labels Ach receptors
Target cell contact results in…
increase presynaptic NT release
cell adhesion
Ca2+ entry
Clustering in NMJ
Is clustering of spinal motor neurons and Ach receptors dependent on acetylcholine? If not, then why do they cluster?
Not acetylcholine
Cluster due to contact
What is the cluster signal?
Agrin (neuronal)
Experiment: Cut axons to basal lamina and remove muscle
Result: new muscle cells will still cluster, meaning the cluster signal is in the synaptic cleft
Argin binds to Lrp4 and MuSK-P, because ___ and ___ needed for clustering
MuSK and Actin
Musk recruits __ and ___ as scaffolding proteins, needed for acetylcholine clustering
Doc7 and Tid1
If musk doesn’t touch raspsyn (anchors postsynaptic side) or AChR what gets it to the right place?
MASC and RATL
If you KO Musk…
lose clusters
What was the point of the chick and rat experiment?
neural agrin is what causes clustering
CNS: what helps with clusters of NMDA and AMPA
1) Ephrin B- Eph B (NMDA)
2) pentroxins (NARP) - AMPA-glutamate to GluR4
3) Neurotrophin- trk: BDNF response, GABA and NMDA clusters.
KO ephrin
don’t get nice AMPA clusters
Glutamate Receptor:
____ adaptor protein for NMDA R
_____ adaptor protein for AMPA
NARP
TARP
Glutamate Receptor: NLGN
binds to gephyrin (NRXIN), activates GDP/GTP exchange factor: COLLYBISTIN, interacts with NLGN2
GABA receptor: early on gephyrin is anchoring ____ to syanpse
alpha-2 Gaba R
GABA receptor: radixin holds ____ extrasynaptically, but loss of radixin does not disrupt clustering
GABA5
Experiment: muscles prelabeled with rhodaneuro-bunganexin.
1) MN added
2) no MN added
Then labeled with fluorescent antibody
Only antibody = new inserted
1) 60% new
2) 20% new
Shows presynaptic terminal causes receptors to come in
Experiment: TXX cuff to bock Na+ so no AP
NO transmission
normally, AP –> Ca2+ –> CAMK2 –> myogenin which inhibits Ach R on neighbors
myogen
transcription fact, inhibits AchR expression in non-synaptic nuclei. If ttx cuff, can’t stop expression
The Ca2+ –> CAMK2 –> myogen activates…
acetyl outside synapse
KO agrin = ________
Can this be saved?
no aggregation
Yes! if we KO acetylcholine too!
Dispersion signal
acetylcholine, activates cdk5 to put receptors in vesicles and inhibits aggregation genes
Since too many glutamate receptors is bad, activity limits glutamate receptors by…
internalizing AMPA
How does activity internalize AMPA?
1) Arc transcribed, AMPA out membrane, pull in to destroy
2) UBe3A: marks Arc for destruction, prevents arc from getting all receptors out
Duration of EPSP and IPSP _____ over time
declines, goes faster so you can respond to new stuff quickly
ErbB receptors and neuregulin do what to acetylcholine receptors
Change that gamma to epsilon over the course of development
Early AP are (more/less) Ca2+ dependent than later ones
more
After switching channel subtypes, time it takes to open/close channels…
decreases
What channels increase over development? Which decrease?
L and N
T decrease
Young glycine vs. adult glycine
young: alpha-2, open long time
adult: alpha-1, short open times
Young GABA vs. Adult GABA
alpha 5 replaced by alpha 1
shorter open times in adult
Experiment: picrotoxin (blocks GABA)
CNQX: blocks AMPA
only EPSP from NMDA
younger have larger lasting EPSP
Ion gradient in cells: Why is Cl- not inhibitory when influx at first? Why hyperpolarization that makes inhibitory?
1) Glia maintain extracellular environment
2) symporters/ion pumps at early stages not good at getting Cl- out so equilibrium is crazy
BIC-GABA receptors antagonists:
(BIC: inhibits transmission)
8 days vs. 33 days
8 days: decrease Ca2+, depolarize
33 days: increase Ca2+, hyperpolarized
Why depolarize IPSP, elevated Cl- in cell, so Cl- outflow
Changing ___ to ___ helps get that Cl- out of the cell.
NKCC1 –> KCC2
______ causes super sensitivity of receptors
denervation/blockade
_____ at NMJ controls transcription of receptor proteins
neuregulin
Maturation changes:
1) receptor Number & subtype
2) ion channel conductance
3) GABA R mediates excitatory transmission in young developing neurons
