Identification and molecular characterization of the Galpha12-Rho guanine nucleotide exchange factor pathway in Caenorhabditis elegans

G-alpha-12/13-mediated pathways have been shown to be involved in various fundamental cellular functions in mammalian cells such as axonal guidance, apoptosis, and chemotaxis. Here, we identified a homologue of Rho-guanine nucleotide exchange factor (GEF) in Caenorhabditis elegans (CeRhoGEF), which functions downstream of gpa-12, the C. elegans homologue of G12/13. CeRhoGEF contains a PSD-95/Dlg/ZO-1 domain and a regulator of G protein signaling (RGS) domain upstream of the Dbl homology-pleckstrin homology region similar to mammalian RhoGEFs with RGS domains, PSD-95/Dlg/ZO-1-RhoGEF and leukemia-associated RhoGEF. It has been shown in mammalian cells that these RhoGEFs interact with activated forms of G12 or G13 through their RGS domains. We demonstrated by coimmunoprecipitation that the RGS domain of CeRhoGEF interacts with GPA-12 in an activation-dependent manner and confirmed that the Dbl homology-pleckstrin homology domain of CeRhoGEF was capable of Rho-dependent signaling. These results proved conservation of the G12-RhoGEF pathway in C. elegans. Expression of DsRed or GFP under the control of the promoter of CeRhoGEF or gpa-12 revealed an overlap of their expression patterns in ventral cord motor neurons and several neurons in the head. RNA-mediated gene interference for CeRhoGEF and gpa-12 resulted in similar phenotypes such as embryonic lethality and sensory and locomotive defects in adults. Thus, the G12/13-RhoGEF pathway is likely to be involved in embryonic development and neuronal function in C. elegans. [PUBLICATION ABSTRACT]