title: Ras-dependent signaling by the GTPase-deficient mutant of Galpha12.
abstract: Galpha12 and Galpha13 regulate diverse responses through the small GTPases Ras, CDC42, Rac, and Rho. Whereas they activate similar responses in many different cell types, they also activate more specific and critical signaling pathways in other cell types. In COS cells, in which both Galpha12 and Galpha13 stimulate Na+/H+ exchange, they do so by activating different signaling pathways. Here we report that the differential recruitment of specific small GTPases by Galpha12 and Galpha13 defines the molecular basis for their functional differences. We have observed that the stimulation of Na+/H+ exchange by the GTPase-deficient mutant of Galpha12 (Galpha12QL) requires a functional Ras and is independent of Rac/CDC42 and Jun kinase signaling module. By contrast, the stimulation of Na+/H+ exchange by Galpha13QL requires a functional Rac/CDC42 and the Jun kinase signaling module. Our results also indicate that Galpha12QL-Ras stimulation of Na+/H+ exchange involves a D609-sensitive phospholipase and protein kinase C. These studies, for the first time, describe a novel Galpha12-specific signaling pathway involving Ras, phosphatidylcholine hydrolysis, and protein kinase C in the regulation of Na+/H+ exchange.
authors.affiliation: Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Wadsworth
authors.forename: G
authors.initials: G
authors.lastname: Gebauer
authors.forename: G D
authors.initials: GD
authors.lastname: van Rossum
authors.forename: N
authors.initials: N
authors.lastname: Dhanasekaran
mesh_terms: D000818:Animals; D019556:COS Cells; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000235:genetics*; D006868:Hydrolysis; D010713:Phosphatidylcholines / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism
chemical_list: D010713:Phosphatidylcholines; D011518:Proto-Oncogene Proteins; D017923:Sodium-Hydrogen Exchangers; D011493:Protein Kinase C; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go