期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：2
页码：733-738
DOI：10.1073/pnas.0234057100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Heterotrimeric G proteins, G12 and G13, have been shown to transduce signals from G protein-coupled receptors to activate Rho GTPase in cells. Recently, we identified p115RhoGEF, one of the guanine nucleotide exchange factors (GEFs) for Rho, as a direct link between G13 and Rho [Kozasa, T., et al. (1998) Science 280, 2109-2111; Hart, M. J., et al. (1998) Science 280, 2112-2114]. Activated G13 stimulated the RhoGEF activity of p115 through interaction with the N-terminal RGS domain. However, G12 could not activate Rho through p115, although it interacted with the RGS domain of p115. The biochemical mechanism from G12 to Rho activation remained unknown. In this study, we analyzed the interaction of leukemia-associated RhoGEF (LARG), which also contains RGS domain, with G12 and G13. RGS domain of LARG demonstrated G12- and G13-specific GAP activity. LARG synergistically stimulated SRF activation by G12 and G13 in HeLa cells, and the SRF activation by G12-LARG was further stimulated by coexpression of Tec tyrosine kinase. It was also found that LARG is phosphorylated on tyrosine by Tec. In reconstitution assays, the RhoGEF activity of nonphosphorylated LARG was stimulated by G13 but not G12. However, when LARG was phosphorylated by Tec, G12 effectively stimulated the RhoGEF activity of LARG. These results demonstrate the biochemical mechanism of Rho activation through G12 and that the regulation of RhoGEFs by heterotrimeric G proteins G12/13 is further modulated by tyrosine phosphorylation.
