title: Connexin43 recruits PTEN and Csk to inhibit c-Src activity in glioma cells and astrocytes.
abstract: Connexin43 (Cx43), the major protein forming gap junctions in astrocytes, is reduced in high-grade gliomas, where its ectopic expression exerts important effects, including the inhibition of the proto-oncogene tyrosine-protein kinase Src (c-Src). In this work we aimed to investigate the mechanism responsible for this effect. The inhibition of c-Src requires phosphorylation at tyrosine 527 mediated by C-terminal Src kinase (Csk) and dephosphorylation at tyrosine 416 mediated by phosphatases, such as phosphatase and tensin homolog (PTEN). Our results showed that the antiproliferative effect of Cx43 is reduced when Csk and PTEN are silenced in glioma cells, suggesting the involvement of both enzymes. Confocal microscopy and immunoprecipitation assays confirmed that Cx43, in addition to c-Src, binds to PTEN and Csk in glioma cells transfected with Cx43 and in astrocytes. Pull-down assays showed that region 266-283 in Cx43 is sufficient to recruit c-Src, PTEN and Csk and to inhibit the oncogenic activity of c-Src. As a result of c-Src inhibition, PTEN was increased with subsequent inactivation of Akt and reduction of proliferation of human glioblastoma stem cells. We conclude that the recruitment of Csk and PTEN to the region between residues 266 and 283 within the C-terminus of Cx43 leads to c-Src inhibition.
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: González-Sánchez
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Myriam
authors.initials: M
authors.lastname: Jaraíz-Rodríguez
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Domínguez-Prieto
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Herrero-González
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Medina
authors.affiliation: Instituto de Neurociencias de Castilla y León (INCYL), Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Arantxa
authors.initials: A
authors.lastname: Tabernero
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism*; D000081247:CSK Tyrosine-Protein Kinase; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D014411:Neoplastic Stem Cells / Q000166:cytology; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D010766:Phosphorylation; D016548:Prosencephalon / Q000166:cytology; D000072417:Protein Domains; D000090063:Proto-Oncogene Mas; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014443:Tyrosine / Q000737:chemistry; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D018031:Connexin 43; C500216:GJA1 protein, human; C580592:Gja1 protein, rat; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D014443:Tyrosine; D000081247:CSK Tyrosine-Protein Kinase; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; C000631346:CSK protein, human; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C487216:Pten protein, rat
keywords: CNS; Src; connexin; gap junctions; glia