title: The gap junction channel protein connexin 43 is covalently modified and regulated by SUMOylation.
abstract: SUMOylation is a posttranslational modification in which a member of the small ubiquitin-like modifier (SUMO) family of proteins is conjugated to lysine residues in specific target proteins. Most known SUMOylation target proteins are located in the nucleus, but there is increasing evidence that SUMO may also be a key determinant of many extranuclear processes. Gap junctions consist of arrays of intercellular channels that provide direct transfer of ions and small molecules between adjacent cells. Gap junction channels are formed by integral membrane proteins called connexins, of which the best-studied isoform is connexin 43 (Cx43). Here we show that Cx43 is posttranslationally modified by SUMOylation. The data suggest that the SUMO system regulates the Cx43 protein level and the level of functional Cx43 gap junctions at the plasma membrane. Cx43 was found to be modified by SUMO-1, -2, and -3. Evidence is provided that the membrane-proximal lysines at positions 144 and 237, located in the Cx43 intracellular loop and C-terminal tail, respectively, act as SUMO conjugation sites. Mutations of lysine 144 or lysine 237 resulted in reduced Cx43 SUMOylation and reduced Cx43 protein and gap junction levels. Altogether, these data identify Cx43 as a SUMOylation target protein and represent the first evidence that gap junctions are regulated by the SUMO system.
authors.affiliation: Department of Cancer Prevention, Institute for Cancer Research, Oslo University Hospital, Norway.
authors.forename: Ane
authors.initials: A
authors.lastname: Kjenseth
authors.forename: Tone A
authors.initials: TA
authors.lastname: Fykerud
authors.forename: Solveig
authors.initials: S
authors.lastname: Sirnes
authors.forename: Jarle
authors.initials: J
authors.lastname: Bruun
authors.forename: Zeremariam
authors.initials: Z
authors.lastname: Yohannes
authors.forename: Matthias
authors.initials: M
authors.lastname: Kolberg
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Omori
authors.forename: Edgar
authors.initials: E
authors.lastname: Rivedal
authors.forename: Edward
authors.initials: E
authors.lastname: Leithe
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008239:Lysine / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009154:Mutation; D011499:Protein Processing, Post-Translational; D051381:Rats; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism; D058207:Sumoylation; D014162:Transfection
chemical_list: D018031:Connexin 43; D025842:SUMO-1 Protein; C529669:SUMO2 protein, rat; C529670:SUMO3 protein, rat; D025841:Small Ubiquitin-Related Modifier Proteins; D008239:Lysine