title: Human p63RhoGEF, a novel RhoA-specific guanine nucleotide exchange factor, is localized in cardiac sarcomere.
abstract: The Rho small GTPases are crucial proteins involved in regulation of signal transduction cascades from extracellular stimuli to cell nucleus and cytoskeleton. It has been reported that these GTPases are directly associated with cardiovascular disorders. In this context, we have searched for novel modulators of Rho GTPases, and here we describe p63RhoGEF a new Db1-like guanine nucleotide exchange factor (GEF). P63RhoGEF encodes a 63 kDa protein containing a Db1 homology domain in tandem with a pleckstrin homology domain and is most closely related to the second Rho GEF domain of Trio. Northern blot and in situ analysis have shown that p63RhoGEF is mainly expressed in heart and brain. In vitro guanine nucleotide exchange assays have shown that p63RhoGEF specifically acts on RhoA. Accordingly, p63RhoGEF expression induces RhoA-dependent stress fiber formation in fibroblasts and in H9C2 cardiac myoblasts. Moreover, we show that p63RhoGEF activation of RhoA in intact cells is dependent on the presence of the PH domain. Using a specific anti-p63RhoGEF antibody, we have detected the p63RhoGEF protein by immunocytochemistry in human heart and brain tissue sections. Confocal microscopy shows that p63RhoGEF is located in the sarcomeric I-band mainly constituted of cardiac sarcomeric actin. Together, these results show that p63RhoGEF is a RhoA-specific GEF that may play a key role in actin cytoskeleton reorganization in different tissues, especially in heart cellular morphology.
authors.affiliation: SmithKline Beecham Laboratoires Pharmaceutiques, Unité de Biologie Cardiovasculaire, 4 rue du Chesnay Beauregard, BP 96205, 35760 Saint-Grégoire, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Souchet
authors.forename: Elodie
authors.initials: E
authors.lastname: Portales-Casamar
authors.forename: David
authors.initials: D
authors.lastname: Mazurais
authors.forename: Susanne
authors.initials: S
authors.lastname: Schmidt
authors.forename: Isabelle
authors.initials: I
authors.lastname: Léger
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Javré
authors.forename: Philippe
authors.initials: P
authors.lastname: Robert
authors.forename: Isabelle
authors.initials: I
authors.lastname: Berrebi-Bertrand
authors.forename: Antoine
authors.initials: A
authors.lastname: Bril
authors.forename: Bernard
authors.initials: B
authors.lastname: Gout
authors.forename: Anne
authors.initials: A
authors.lastname: Debant
authors.forename: Thierry P G
authors.initials: TP
authors.lastname: Calmels
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002460:Cell Line; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D017930:Genes, Reporter; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010802:Phylogeny; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D012518:Sarcomeres / Q000378:metabolism*; D016415:Sequence Alignment; D022502:Stress Fibers / Q000378:metabolism; D014018:Tissue Distribution; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C475063:ARHGEF25 protein, human; D020662:Guanine Nucleotide Exchange Factors; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D020742:rhoA GTP-Binding Protein