Depolarization-induced signaling to Ras, Rap1 and MAPKs in cortical neurons.
In neurons, membrane depolarization triggers pleiotropic signaling which includes the activation of the small GTPases, Ras and Rap1, and the mitogen-activated protein kinases (MAPKs) Erk1/2. We have studied the intracellular signaling mechanisms which regulate these events in mouse-cultured cortical neurons. We show that depolarization induces activation of both Ras and Rap1, although with different kinetics: Ras activation is strong and fast while Rap1 activation is slower and weaker. Blockade of calmodulin affects the GTP-loading of Ras and Rap1 and prevents the MAPK response. Moreover, protein kinase A (PKA) activity is required for depolarization-induced Rap1 activation and full Erk stimulation, but is not involved in that of Ras. This PKA-dependent Rap1 activation does not require Src family kinases, but, in contrast to Ras, is sensitive to genistein, indicating the involvement of a tyrosine kinase-dependent mechanism. Our data provide new insights into the regulation of Ras and Rap1 activation in neurons.
Department of Biomolecular Sciences and Biotechnology, University of Milan, via Celoria 26, 20133 Milan, Italy.
Simona
S
Baldassa
Renata
R
Zippel
Emmapaola
E
Sturani
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005333:Fetus; D019833:Genistein / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D020794:Receptor Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
D015220:Calcium Channels; D002147:Calmodulin; D006160:Guanosine Triphosphate; D019833:Genistein; D020794:Receptor Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins