Activation of Gz attenuates Rap1-mediated differentiation of PC12 cells.
We previously identified a specific activation-dependent interaction between the alpha subunit of the heterotrimeric G protein, G(z), and a regulator of Rap1 signaling, Rap1GAP (Meng, J., Glick, J. L., Polakis, P., and Casey, P. J. (1999) J. Biol. Chem. 274, 36663-36669). We now demonstrate that activated forms of Galpha(z) are able to recruit Rap1GAP from a cytosolic location to the membrane. Using PC12 cells as a model for neuronal differentiation, the influence of G(z) activation on Rap1-mediated cell differentiation was examined. Introduction of constitutively-activated Galpha(z) into PC12 cells markedly attenuated the differentiation process of these cells induced by a cAMP analogue. Treatment of PC12 cells expressing wild type Galpha(z) with a specific agonist to the alpha(2A)-adrenergic receptor also attenuated cAMP-induced PC12 cell differentiation, demonstrating that receptor-mediated activation of G(z) was also effective in this regard. Furthermore, activation of G(z) decreased the ability of the cAMP analogue to trigger both Rap1 and extracellular-regulated kinase (ERK) activation. Differentiation of PC12 cells induced by nerve growth factor (NGF) is also thought to be a Rap1-mediated process, and G(z) activation was found to attenuate this process as well. Rap1 activation, ERK phosphorylation, and PC12 cell differentation induced by NGF treatment were all significantly attenuated by either transfection of constitutively activated Galpha(z) or receptor-mediated G(z) activation. Based on these findings, a model is proposed in which activation of G(z) results in recruitment of Rap1GAP to the membrane where it can effectively down-regulate Rap1 signaling. The implications of these findings in regard to a possible role for G(z) in neuronal development are discussed.
Meng
Jingwei
J
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Casey
Patrick J
PJ
D000246:Adenosine Diphosphate Ribose / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008959:Models, Neurological; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000502:physiology; D016716:PC12 Cells; D037342:Pertussis Toxin / Q000494:pharmacology; D010673:Pheochromocytoma; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D018411:Spodoptera; D014162:Transfection; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
C099387:GNAZ protein, human; D044385:GTP-Binding Protein alpha Subunits; C490963:Gnaz protein, rat; D011994:Recombinant Proteins; D000246:Adenosine Diphosphate Ribose; D020932:Nerve Growth Factor; D037342:Pertussis Toxin; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins