Nerve growth factor action is mediated by cyclic AMP- and Ca+2/phospholipid-dependent protein kinases.
Nerve growth factor (NGF) mediates the phosphorylation of tyrosine hydroxylase in PC12 cells on two distinct peptide fragments, separable by two-dimensional tryptic phosphopeptide mapping (phosphopeptides T1 and T3). Phorbol diester derivatives capable of activating Ca+2/phospholipid-dependent protein kinase (C-kinase) cause a specific phosphorylation of peptide T3 in a dose-dependent, saturable manner. Derivatives of the endogenous C-kinase activator diacylglycerol, also cause the phosphorylation of tyrosine hydroxylase on peptide T3. The C-kinase inhibitors chlorpromazine and trifluoperazine inhibit the phorbol diester stimulated phosphorylation of site T3 in a dose-dependent manner. These agents inhibit the phosphorylation of T3 in response to NGF, but have no effect on NGF's ability to cause T1 phosphorylation. In a PC12 mutant deficient in cAMP-dependent protein kinase activity, NGF mediates the phosphorylation of tyrosine hydroxylase on peptide T3 but not on T1. We conclude that NGF mediates the activation of both the cAMP-dependent protein kinase and the C-kinase to phosphorylate substrate proteins. These kinases can act independently to phosphorylate tyrosine hydroxylase, each at a different site, and each of which results in the enzyme activation. A molecular framework is thus provided for events underlying NGF action.
D000818:Animals; D002460:Cell Line; D002746:Chlorpromazine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D009414:Nerve Growth Factors / Q000378:metabolism*; D010673:Pheochromocytoma / Q000648:ultrastructure; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D014268:Trifluoperazine / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D009414:Nerve Growth Factors; D014268:Trifluoperazine; D000242:Cyclic AMP; D014446:Tyrosine 3-Monooxygenase; D011494:Protein Kinases; D011493:Protein Kinase C; D002746:Chlorpromazine