Activation of Rho GEF activity by Gα13

Abstract

Publisher Summary This chapter describes the activation of Rho guanine nucleotide exchange factors (GEF) by Gcα 13 .Rho activity is largely determined by GEFs. It allows formation of the effective Rho–GTP complex by causing displacement of GDP from the inactive, ambient Rho–GDP complex. Rho GTPase plays a key role in organizing the cytoskeleton of eukaryotic cells. In particular, Rho directs the assembly of actin–myosin stress fibers and focal adhesion complexes that in turn mediate important intra- and inter-cellular signaling events. Because Rho activity is determined primarily by Rho GEFs, the regulation of Rho GEF activity must play a critical role in these pathways. The chapter describes robust assays for determining Rho GEF activity and applies these assays to biochemically analyze Rho GEFs. Binding of extracellular factors (such as lysophosphatidic acid) to heptahelical receptors results in activation of heterotrimeric G-proteins of the α I3 family. This event triggers a pathway leading to Rho activation. Specifically, the Gα 13 protein binds directly to the RGS domain of p115 Rho GEF, affecting an increase in GEF activity. Because the Rho pathway plays important roles in pathologies such as hypertension and cancer, the Gα l3 / Rho GEF interaction makes an attractive therapeutic target.