process extension/growth cone Flashcards
what are the three steps of process navigation
detection of ligand and receptor
cytoplasmic signaling
motile response
what is involved in detection of ligand by the receptor
growth factors, chemoattractant and ECM. PTK receptors, cell adhesion molecules and neurotransmitters
what is involved in cytoplasmic signaling
calcium influx, protein kinase phosphatase, Rho/Rac/CDC42, IP3 and PIP2
what is involved in motile responses
actin-myosin and binding proteins, microtubules and binding proteins, GAP43 (growth associated protein), membrane flow
how is Rho active?
when bound to GTP
what causes faster turnover of Rho activity?
Rho GAP.
what causes slower Rho activity
Rho GDI
GDP-dissociation inhibitor
what causes increased Rho activity
Rho GEF. GTP exchange factor
what factors activate neurite extension, what evidence
Rac, CDC42, RhoG
activated versions enhance neurite outgrowth
what factors inhibit neurite extension or cause neurite retraction, evidence
RhoA
clostridium, blocks RhoA, blocks growth cone collapse
what does Rac do and in what cellular system
actin polymerization in the lamelipodia
what does Rho do and in whatcellular system
actin bundling in stress fibers
what does CDC42 do and in what cellular system
actin polymerization in filapodia
CDC42 mechanism
binds PIP2 and N-WASP and uses GTP to activate Arp2/3 to cause branching of actin filaments (70 degrees)
Rho family mechanism
rho family activity causes confirmational change in ERM (ezrin, radixin, moesin) proteins which causes binding to icams and F-actin
regulation of cofilin by Rho family
activation of Rho activates LIMK which stabilizes actin polymerization by phosphorylating cofilin.
regulation of cofilin by Rac
same as Rho family
how does slingshot regulate cofilin
it dephosphorylates cofilin which then causes F-actin severing and depolarization
ENA/Vasp proteins in process extension
binds Lpd membrane proteins, linking them to F-actin. this stabilizes the association between the membrane and F-actin
how do Rho family proteins regulate actin polymerizatoin
through activation of PAK, WASP, ERM and cofilin
how do ENA/VASP proteins regulate actin dynamics
cell surface receptor, actin/profilin binding, filamentous actin binding, by blocking actin capping proteins
how does membrane flow work in process extensino
1) membrane is endocytosed from areas not actively extending
2) membrane is generated de novo and transported through the golgi network
secretory mutants cause defects in what?
dendrites, not axons.
laser ablation of golgi outposts cause dendrite outgrowth defects.
what regulates kinesin-dependent axonal growth
UNC-69/73. they link kinesin motors to vesicles
what is an intact secretory pathway required for?
dendritogenesis
does ER-to-golgi transport affect growth of axons
no
dendritic branches require what
golgi outposts
how are microtubules oriented in axons
in a uniform manner plus-end-distal.
what are par genes for
asymmetric orientations. they distinguish anterior and posterior poles of the embryo
par1
S/T kinase MARK in mammals
par 2
ring finger protein (ubiquitin pathway
par3
PDZ domain protein (scaffold)
par 4
S/T kinase (LKB1 in mammals)
par5
member of the 14-3-3 pathway
par6
PDZ scaffold
par 3/6 localization
apical pole
par 1/2
localized to lateral basal
par 4/5
equally distributed
are distinct domains actively maintained? how?
yes. by phosphorylation
apical domain sequestration
aPKC phosphorylates par-1 leading to par-5 binding, preventing association with the membrane
lateral domain
par-1 phosphorylates par-3 releasing it from the membrane
what proteins are required for establishing the apical/basal regions
par proteins, aPKC/CDC42
what is the first polarizing event in neurons
axonogenesis
what happens when you sever an axon
new axon formatino
what factor causes supranumery axons
cytochalazin D
where does mPar6 localize
tip of nascent axon
what factor is required for axon initiation
aPKC
what can we inhibit to block polarization
PI3K
how is LKB1 regulated
binding STRAD and MO25 recruits it to the cytoplasm, stabilizes it and activates it kinase activity
what are the downstream substrates of LKB1
MARK (Par1) and SAD kinases
what does inactivation of LKB1 causes what
peutz-Jaghers cancer syndrome
what does STRAD expression do
stabilizes LKB1 in one process prior to axon specification
what happens when LKB1 inactivated
loss of axon initiation
LKB1 + STRAD = ?
more axons
how is axon/dendrite polarity initiated
neuronal migration
