title: Connexin43 phosphorylation by PKC and MAPK signals VEGF-mediated gap junction internalization.
abstract: Gap junctions (GJs) exhibit a complex modus of assembly and degradation to maintain balanced intercellular communication (GJIC). Several growth factors, including vascular endothelial growth factor (VEGF), have been reported to disrupt cell-cell junctions and abolish GJIC. VEGF directly stimulates VEGF-receptor tyrosine kinases on endothelial cell surfaces. Exposing primary porcine pulmonary artery endothelial cells (PAECs) to VEGF for 15 min resulted in a rapid and almost complete loss of connexin43 (Cx43) GJs at cell-cell appositions and a concomitant increase in cytoplasmic, vesicular Cx43. After prolonged incubation periods (60 min), Cx43 GJs reformed and intracellular Cx43 were restored to levels observed before treatment. GJ internalization correlated with efficient inhibition of GJIC, up to 2.8-fold increased phosphorylation of Cx43 serine residues 255, 262, 279/282, and 368, and appeared to be clathrin driven. Phosphorylation of serines 255, 262, and 279/282 was mediated by MAPK, whereas serine 368 phosphorylation was mediated by PKC. Pharmacological inhibition of both signaling pathways significantly reduced Cx43 phosphorylation and GJ internalization. Together, our results indicate that growth factors such as VEGF activate a hierarchical kinase program--including PKC and MAPK--that induces GJ internalization via phosphorylation of well-known regulatory amino acid residues located in the Cx43 C-terminal tail.
authors.affiliation: Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015.
authors.forename: Wutigri
authors.initials: W
authors.lastname: Nimlamool
authors.affiliation: Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015.
authors.forename: Rachael M Kells
authors.initials: RM
authors.lastname: Andrews
authors.affiliation: Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015 MFalk@lehigh.edu.
authors.forename: Matthias M
authors.initials: MM
authors.lastname: Falk
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism*; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D013552:Swine; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D018031:Connexin 43; C500216:GJA1 protein, human; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases