title: LARG links histamine-H1-receptor-activated Gq to Rho-GTPase-dependent signaling pathways.
abstract: Activation of heterotrimeric G proteins, such as G(12/13) and G(q), by cell surface receptors is coupled to the regulation of numerous cellular functions controlled by activated Rho GTPases. Previous studies have implicated the Rho guanine nucleotide exchange factor (RhoGEF) leukemia-associated RhoGEF (LARG) as a regulatory protein receiving stimulatory inputs from activated Gα(12/13) and Gα(q). However, the molecular mechanisms of the Gα(q)-mediated LARG activation are not fully understood and the structural elements of LARG involved in this process have remained unclear. In the present work, the specific coupling of the histamine H1 receptor (HRH1) exogenously expressed in COS-7 cells to G(q), but not to G(12/13), was used to conduct a detailed analysis of receptor- and Gα(q)-mediated LARG activation and to define its structural requirements. The results show that HRH1-mediated activation of the strictly Rho-dependent transcriptional activity of serum response factor requires the PDZ domain of LARG and can be mimicked by activated Gα(q)(Q209L). The functional interaction between activated Gα(q) and LARG requires no more than the catalytic DH-PH tandem of LARG, and is independent of PLCβ activation and distinct from the mechanisms of Gα(q)-mediated p63RhoGEF and PLCβ(3) activation. Activated Gα(q) physically interacts with the relevant portions of LARG in COS-7 cells and histamine causes activation of LARG in native HeLa cells endogenously expressing HRH1, G(q), and LARG. This work is the first positive demonstration of a stimulatory effect of LARG on the ability of a strictly G(q)-coupled receptor to cause activation of a Rho-GTPase-dependent signaling pathway.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany.
authors.forename: Mariana
authors.initials: M
authors.lastname: Pfreimer
authors.forename: Petra
authors.initials: P
authors.lastname: Vatter
authors.forename: Torben
authors.initials: T
authors.lastname: Langer
authors.forename: Thomas
authors.initials: T
authors.lastname: Wieland
authors.forename: Peter
authors.initials: P
authors.lastname: Gierschik
authors.forename: Barbara
authors.initials: B
authors.lastname: Moepps
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D054731:PDZ Domains; D054799:Phospholipase C beta / Q000378:metabolism; D011969:Receptors, Histamine H1 / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D026362:Serum Response Factor / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C577222:ARHGEF12 protein, human; D020662:Guanine Nucleotide Exchange Factors; D011969:Receptors, Histamine H1; D064067:Rho Guanine Nucleotide Exchange Factors; D026362:Serum Response Factor; D054799:Phospholipase C beta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020741:rho GTP-Binding Proteins