title: Activation of Jun kinase/stress-activated protein kinase by GTPase-deficient mutants of G alpha 12 and G alpha 13.
abstract: Signal transduction pathways regulated by G12 and G13 heterotrimeric G proteins are largely unknown. Expression of activated, GTPase-deficient mutants of alpha 12 and alpha 13 alter physiological responses such as Na+/H+ exchanger activity, but the effector pathways controlling these responses have not been defined. We have found that the expression of GTPase-deficient mutants of alpha 12 (alpha 12Q229L) or alpha 13 (alpha 13Q226L) leads to robust activation of the Jun kinase/stress-activated protein kinase (JNK/SAPK) pathway. Inducible alpha 12Q229L and alpha 13Q226L expression vectors stably transfected in NIH 3T3 cells demonstrated JNK/SAPK activation but not extracellular response/mitogen-activated protein kinase activation. Transient transfection of alpha 12Q229L and alpha 13Q226L also activated the JNK/SAPK pathway in COS-1 cells. Expression of the GTPase-deficient mutant of alpha q (alpha qQ209L) but not alpha i (alpha iQ205L) or alpha s (alpha sQ227L) was also able to activate the JNK/SAPK pathway. Functional Ras signaling was required for alpha 12Q229L and alpha 13Q226L activation of the JNK/SAPK pathway; expression of competitive inhibitory N17Ras inhibited JNK/SAPK activation in response to both alpha 12Q229L and alpha 13Q226L. The results describe for the first time a Ras-dependent signal transduction pathway involving JNK/SAPK regulated by alpha 12 and alpha 13.
authors.affiliation: Fels Institute for Cancer Research and Molecular Biology, Temple University, School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Prasad
authors.forename: J M
authors.initials: JM
authors.lastname: Dermott
authors.forename: L E
authors.initials: LE
authors.lastname: Heasley
authors.forename: G L
authors.initials: GL
authors.lastname: Johnson
authors.forename: N
authors.initials: N
authors.lastname: Dhanasekaran
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000172:deficiency* / Q000235:genetics; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009154:Mutation; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D018631:ras Proteins