title: Leukemia-associated Rho guanine nucleotide exchange factor promotes G alpha q-coupled activation of RhoA.
abstract: Leukemia-associated Rho guanine-nucleotide exchange factor (LARG) belongs to the subfamily of Dbl homology RhoGEF proteins (including p115 RhoGEF and PDZ-RhoGEF) that possess amino-terminal regulator of G protein signaling (RGS) boxes also found within GTPase-accelerating proteins (GAPs) for heterotrimeric G protein alpha subunits. p115 RhoGEF stimulates the intrinsic GTP hydrolysis activity of G alpha 12/13 subunits and acts as an effector for G13-coupled receptors by linking receptor activation to RhoA activation. The presence of RGS box and Dbl homology domains within LARG suggests this protein may also function as a GAP toward specific G alpha subunits and couple G alpha activation to RhoA-mediating signaling pathways. Unlike the RGS box of p115 RhoGEF, the RGS box of LARG interacts not only with G alpha 12 and G alpha 13 but also with G alpha q. In cellular coimmunoprecipitation studies, the LARG RGS box formed stable complexes with the transition state mimetic forms of G alpha q, G alpha 12, and G alpha 13. Expression of the LARG RGS box diminished the transforming activity of oncogenic G protein-coupled receptors (Mas, G2A, and m1-muscarinic cholinergic) coupled to G alpha q and G alpha 13. Activated G alpha q, as well as G alpha 12 and G alpha 13, cooperated with LARG and caused synergistic activation of RhoA, suggesting that all three G alpha subunits stimulate LARG-mediated activation of RhoA. Our findings suggest that the RhoA exchange factor LARG, unlike the related p115 RhoGEF and PDZ-RhoGEF proteins, can serve as an effector for Gq-coupled receptors, mediating their functional linkage to RhoA-dependent signaling pathways.
authors.affiliation: Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 27599, USA. mbooden@med.unc.edu
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Booden
authors.forename: David P
authors.initials: DP
authors.lastname: Siderovski
authors.forename: Channing J
authors.initials: CJ
authors.lastname: Der
mesh_terms: D016475:3T3 Cells; D020816:Amino Acid Motifs; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C577223:Arhgef12 protein, mouse; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C115270:G2A receptor; D020662:Guanine Nucleotide Exchange Factors; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; D064067:Rho Guanine Nucleotide Exchange Factors; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein