title: Involvement of cAMP in nerve growth factor-triggered p35/Cdk5 activation and differentiation in PC12 cells.
abstract: The signaling mechanisms underlying cell differentiation have been extensively studied with the use of rat PC12 cells as a model system. Nerve growth factor (NGF) is a trophic factor inducing PC12 cell differentiation through the activation of the p35/cyclin-dependent kinase 5 (Cdk5) complex. It has been reported that adenylyl cyclase activation and cAMP production may be involved in NGF-dependent actions. Our previous results indicate that cAMP activates the p35/Cdk5 complex in reproductive cells. Therefore, the role of cAMP in NGF-triggered p35/Cdk5 activation and PC12 differentiation was interesting to explore. Our results indicate that roscovitine, a molecular inhibitor of Cdk5, blocks cAMP-triggered PC12 differentiation, which was evaluated by neurite initiation, a decrease in proliferation, and cell cycle G(1) arrest. The following data show that cAMP treatment increased Cdk5 activity through p35 upregulation. cAMP downstream components, protein kinase A (PKA) and phosphorylated cAMP response element binding protein (CREB), are involved in this regulation. The immunocytochemical results indicate that PKA inhibition disrupted cAMP-triggered p35/Cdk5 localization in PC12 cells. In addition, adenylyl cyclase inhibition was found to diminish NGF-induced intracellular cAMP production, CREB phosphorylation, and p35 expression. The cAMP antagonist and the PKA inhibitors reduced NGF-induced p35 expression. Finally, NGF-triggered PC12 differentiation was partially decreased by adenylyl cyclase or PKA inhibitors. In conclusion, these results demonstrate that cAMP may play a role in NGF-p35/Cdk5-dependent PC12 differentiation.
authors.affiliation: Dept. of Physiology, School of Medicine, National Yang Ming University, Taipei 11221, Taiwan, Republic of China.
authors.forename: Mei-Chih
authors.initials: MC
authors.lastname: Chen
authors.forename: Ho
authors.initials: H
authors.lastname: Lin
authors.forename: Fu-Ning
authors.initials: FN
authors.lastname: Hsu
authors.forename: Pao-Hsuan
authors.initials: PH
authors.lastname: Huang
authors.forename: Guan-Shun
authors.initials: GS
authors.lastname: Lee
authors.forename: Paulus S
authors.initials: PS
authors.lastname: Wang
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology* / Q000502:physiology; D051360:Cyclin-Dependent Kinase 5 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D020932:Nerve Growth Factor / Q000494:pharmacology* / Q000502:physiology; D016501:Neurites / Q000187:drug effects / Q000201:enzymology; D016716:PC12 Cells; D010770:Phosphotransferases / Q000378:metabolism*; D011687:Purines / Q000494:pharmacology; D051381:Rats; D000077546:Roscovitine
chemical_list: C492235:Cdk5r1 protein, rat; D011687:Purines; D000077546:Roscovitine; D020932:Nerve Growth Factor; D000242:Cyclic AMP; D010770:Phosphotransferases; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat