title: Role of Lbc RhoGEF in Galpha12/13-induced signals to Rho GTPase.
abstract: Heterotrimeric Galpha12/13 signals induce cellular responses such as serum response element (SRE)-mediated gene transcription via Rho GTPase. Guanine nucleotide exchange factors (GEFs) are strong candidates for linking Galpha signals to Rho. For example, p115 RhoGEF transduces Galpha13 signals to Rho and inhibits Galpha12/13 signals via the RhoGEF LH domain which links to Galpha subunits. Here, we have evaluated the signaling capacity of Lbc RhoGEF in the context of Galpha12/13 signals. In vitro GEF assays indicate that baculoviral-expressed proto-Lbc has minimal exchange activity, implying that a stimulus is required for Lbc activity in vivo. Expression of a catalytically inactive proto-Lbc mutant in HEK293T cells attenuates Galpha12- and thrombin-induced activation of an SRE transcriptional reporter, and the levels of inhibition observed is similar to that obtained with an analogous p115 RhoGEF mutant. proto-Lbc mutant expression also led to decreased levels of Galpha12-induced RhoA activation in vivo. Complex formation between Galpha12 and Lbc forms was detected. Analysis of the Lbc peptide sequence reveals a previously undetected region which may link to Galpha subunit signals. These findings support a role for Lbc in Galpha12-induced signaling pathways to Rho.
authors.affiliation: Physiology Department, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Parmesh
authors.initials: P
authors.lastname: Dutt
authors.forename: Nhan
authors.initials: N
authors.lastname: Nguyen
authors.forename: Deniz
authors.initials: D
authors.lastname: Toksoz
mesh_terms: D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002478:Cells, Cultured; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000494:pharmacology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D017386:Sequence Homology, Amino Acid; D027602:Serum Response Element / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013917:Thrombin / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; C576600:ARHGEF1 protein, human; D048868:Adaptor Proteins, Signal Transducing; D020662:Guanine Nucleotide Exchange Factors; D015778:Minor Histocompatibility Antigens; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D013917:Thrombin; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020741:rho GTP-Binding Proteins