title: Increased interaction of connexin43 with zonula occludens-1 during inhibition of gap junctions by G protein-coupled receptor agonists.
abstract: Astrocytes are extensively coupled through gap junctions (GJs) that are composed of channels mostly constituted by connexin43 (Cx43). This astroglial gap junctional intercellular communication (GJIC) allows propagation of ions and signaling molecules critical for neuronal activity and survival. It is drastically inhibited by a short-term exposure to endothelin-1 (ET-1) or to sphingosine-1-phosphate (S1P), both compounds being inflammatory mediators acting through activation of GTP-binding protein-coupled receptors (GPCRs). Previously, we have identified the GTPases G(i/o) and Rho as key actors in the process of S1P-induced inhibition. Here, we asked whether similar mechanisms underlied the effects of ET-1 and S1P by investigating changes in the phosphorylation status of Cx43 and in the molecular associations of Cx43 with zonula occludens (ZO) proteins and occludin. We showed that the inhibitory effect of ET-1 on GJIC was entirely dependent on the activation of G(i/o) but not on Rho and Rho-associated kinase. Both ET-1 and S1P induced dephosphorylation of Cx43 located at GJs through a process mediated by G(i/o) and calcineurin. Thanks to co-immunoprecipitation approaches, we found that a population of Cx43 (likely junctional Cx43) was associated to ZO-1-ZO-2-occludin multiprotein complexes and that acute treatments of astrocytes with ET-1 or S1P induced a G(i/o)-dependent increase in the amount of Cx43 linked to these complexes. As a whole, this study identifies a new mechanism of GJIC regulation in which two GPCR agonists dynamically alter interactions of Cx43 with its molecular partners.
authors.affiliation: College de France, Center for Interdisciplinary Research in Biology (CIRB), CNRS UMR 7241, INSERM U1050, Paris, France. martine.tence@gmail.com
authors.forename: Martine
authors.initials: M
authors.lastname: Tencé
authors.forename: Pascal
authors.initials: P
authors.lastname: Ezan
authors.forename: Edwige
authors.initials: E
authors.lastname: Amigou
authors.forename: Christian
authors.initials: C
authors.lastname: Giaume
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D015687:Cell Hypoxia; D018031:Connexin 43 / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology / Q000502:physiology; D004789:Enzyme Activation; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D061251:Primary Cell Culture; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000819:agonists*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D018031:Connexin 43; D019332:Endothelin-1; D008246:Lysophospholipids; D008565:Membrane Proteins; D062793:Occludin; C568986:Ocln protein, mouse; D010750:Phosphoproteins; D043562:Receptors, G-Protein-Coupled; C569043:Tjp1 protein, mouse; C569047:Tjp2 protein, mouse; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein; C060506:sphingosine 1-phosphate; D054460:rho-Associated Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020741:rho GTP-Binding Proteins; D013110:Sphingosine