title: EhGEF3, a novel Dbl family member, regulates EhRacA activation during chemotaxis and capping in Entamoeba histolytica.
abstract: Rho GTPases are critical elements involved in the regulation of signal transduction cascades from extracellular stimuli to cytoskeleton. The Rho guanine nucleotide exchange factors (RhoGEFs) have been implicated in direct activation of these GTPases. Here, we describe a novel RhoGEF, denominated EhGEF3 from the parasite Entamoeba histolytica, which encodes a 110 kDa protein containing the domain arrangement of a Dbl homology domain in tandem with a pleckstrin homology domain, the DH domain of EhGEF3 is closely related with the one of the Vav3 protein. Biochemical analysis revealed that EhGEF3 is capable of stimulating nucleotide exchange on the E. histolytica EhRacA and EhRho1 GTPases in vitro, however only a partial GEF activity toward Cdc42 was observed. Conserved residue analysis showed that the N816 and L817 residues are critical for EhGEF3 activity. Cellular studies revealed that EhGEF3 colocalises with EhRacA in the rear of migrating cells, probably regulating the retraction of the uroid and promoting the activation of these GTPase during the chemotactic response toward fibronectin, and that EhGEF3 also regulates EhRacA activation during the capping of cell receptors. These results suggest that EhGEF3 should have a direct role in activating EhRacA, and in bringing the activated GTPase to specific target sites such as the uroid.
authors.affiliation: Departamento de Biomedicina Molecular, CINVESTAV-IPN, Mexico City, Mexico.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Arias-Romero
authors.forename: Claudia H Gonzalez
authors.initials: CH
authors.lastname: de la Rosa
authors.forename: Ma de Jesús
authors.initials: Mde J
authors.lastname: Almaráz-Barrera
authors.forename: Juan D
authors.initials: JD
authors.lastname: Diaz-Valencia
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sosa-Peinado
authors.forename: Miguel
authors.initials: M
authors.lastname: Vargas
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002633:Chemotaxis; D016000:Cluster Analysis; D004748:Entamoeba histolytica / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D004789:Enzyme Activation; D005786:Gene Expression Regulation / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D020744:rac GTP-Binding Proteins