An activated mutant of the alpha subunit of G(o) increases neurite outgrowth via protein kinase C.
The GTP-binding protein, G(o), is present at very high concentration in the neuronal growth cone membrane. The expression of activated mutants of the a subunit of G(o) increases neurite outgrowth. To determine the intracellular mechanism for this outgrowth, we have examined activated alpha o-dependent outgrowth in the presence of agents which modulate different signal transduction cascades. Activation of protein kinase C with phorbol esters or with diacylglycerol prevents the alpha o-dependent increase in neurite extension. Inhibition of protein kinase C with staurosporine, with H7, or with long-term, high dose phorbol ester treatment resulted in greater neurite elongation, and no further increase after activated alpha o transfection. The protein phosphatase inhibitor, okadaic acid, also blocked the effect of activated alpha o. In contrast, tyrosine kinase inhibitors and agents which alter cAMP levels did not alter activated alpha o-dependent neurite extension. We tested a number of compounds which alter intracellular calcium levels. TMB-8 and thapsigargin prevented an increase in outgrowth by activated alpha o, but diltiazem, Bay K8644 and dantrolene had no effect on activated alpha o-dependent outgrowth. These studies suggest that activated alpha o increases neurite outgrowth by inhibiting protein kinase C and by modulating intracellular calcium release.
Xie
R
R
Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA.
Li
L
L
Goshima
Y
Y
Strittmatter
S M
SM
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000648:ultrastructure*; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D009154:Mutation / Q000502:physiology; D016501:Neurites / Q000502:physiology*; D019319:Okadaic Acid; D016716:PC12 Cells / Q000502:physiology* / Q000648:ultrastructure; D011493:Protein Kinase C / Q000819:agonists / Q000502:physiology*; D051381:Rats; D015290:Second Messenger Systems / Q000502:physiology; D019311:Staurosporine; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014162:Transfection
D000470:Alkaloids; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D013729:Terpenes; D019319:Okadaic Acid; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D019284:Thapsigargin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D000252:Calcium-Transporting ATPases; D019311:Staurosporine; D002118:Calcium