title: A Blk-p190RhoGAP signaling module downstream of activated Gα13 functionally opposes CXCL12-stimulated RhoA activation and cell invasion.
abstract: Activation of the GTPase RhoA linked to cell invasion can be tightly regulated following Gα13 stimulation. We have used a cellular model displaying Gα13-dependent inhibition of RhoA activation associated with defective cell invasion to the chemokine CXCL12 to characterize the molecular players regulating these processes. Using both RNAi transfection approaches and protein overexpression experiments here we show that the Src kinase Blk is involved in Gα13-activated tyrosine phosphorylation of p190RhoGAP, which causes RhoA inactivation and ultimately leads to deficient cell invasion. Characterization of molecular interplays between Gα13, Blk and p190RhoGAP revealed that Blk binds Gα13, and that Blk-mediated p190RhoGAP phosphorylation upon Gα13 activation correlates with weakening of Gα13-Blk association connected to increased Blk-p190RhoGAP assembly. These results place Blk upstream of the p190RhoGAP-RhoA pathway in Gα13-activated cells, overall representing an opposing signaling module during CXCL12-triggered invasion. In addition, analyses with Blk- or Gα13-knockdown cells indicated that Blk can also mediate CXCL12-triggered phosphorylation of p190RhoGAP independently of Gα13. However, even if CXCL12 induces the Blk-mediated GAP phosphorylation, the simultaneous stimulation of the guanine-nucleotide exchange factor Vav1 by the chemokine, as earlier reported, leads to a net increase in RhoA activation. Therefore, when Gα13 is concurrently stimulated with CXCL12 there appears to be sufficient Blk activity to promote adequate levels of p190RhoGAP tyrosine phosphorylation to inactivate RhoA and to impair cell invasiveness.
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain.
authors.forename: Rubén A
authors.initials: RA
authors.lastname: Bartolomé
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Díaz-Martínez
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain.
authors.forename: Georgina P
authors.initials: GP
authors.lastname: Coló
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain.
authors.forename: Nohemí
authors.initials: N
authors.lastname: Arellano-Sánchez
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología (CSIC), 28049 Madrid, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Torres-Ayuso
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain.
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Kleinovink
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología (CSIC), 28049 Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Mérida
authors.affiliation: Department of Cellular and Molecular Medicine, Centro de Investigaciones Biológicas (CSIC), 28040 Madrid, Spain. Electronic address: joaquint@cib.csic.es.
authors.forename: Joaquin
authors.initials: J
authors.lastname: Teixidó
mesh_terms: D045744:Cell Line, Tumor; D054377:Chemokine CXCL12 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: C074560:ARHGAP35 protein, human; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D020662:Guanine Nucleotide Exchange Factors; D009363:Neoplasm Proteins; D012097:Repressor Proteins; C066737:RHOA protein, human; C584409:BLK protein, human; D019061:src-Family Kinases; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020742:rhoA GTP-Binding Protein
keywords: Cell invasion; Chemokines; GTPase; Heterotrimeric G proteins; Src