title: Smad ubiquitination regulatory factor-2 controls gap junction intercellular communication by modulating endocytosis and degradation of connexin43.
abstract: Gap junctions consist of arrays of intercellular channels that enable adjacent cells to communicate both electrically and metabolically. Gap junction channels are made of a family of integral membrane proteins called connexins, of which the best-studied member is connexin43. Gap junctions are dynamic plasma membrane domains, and connexin43 has a high turnover rate in most tissue types. However, the mechanisms involved in the regulation of connexin43 endocytosis and transport to lysosomes are still poorly understood. Here, we demonstrate by live-cell imaging analysis that treatment of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) induces endocytosis of subdomains of connexin43 gap junctions. The internalized, connexin43-enriched vesicles were found to fuse with early endosomes, which was followed by transport of connexin43 to the lumen of early endosomes. The HECT E3 ubiquitin ligase smad ubiquitination regulatory factor-2 (Smurf2) was found to be recruited to connexin43 gap junctions in response to TPA treatment. Depletion of Smurf2 by small interfering RNA resulted in enhanced levels of connexin43 gap junctions between adjacent cells and increased gap junction intercellular communication. Smurf2 depletion also counteracted the TPA-induced endocytosis and degradation of connexin43. Collectively, these data identify Smurf2 as a novel regulator of connexin43 gap junctions.
authors.affiliation: Department of Cancer Prevention, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0310 Oslo, and Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: Tone Aase
authors.initials: TA
authors.lastname: Fykerud
authors.forename: Ane
authors.initials: A
authors.lastname: Kjenseth
authors.forename: Kay Oliver
authors.initials: KO
authors.lastname: Schink
authors.forename: Solveig
authors.initials: S
authors.lastname: Sirnes
authors.forename: Jarle
authors.initials: J
authors.lastname: Bruun
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Omori
authors.forename: Andreas
authors.initials: A
authors.lastname: Brech
authors.forename: Edgar
authors.initials: E
authors.lastname: Rivedal
authors.forename: Edward
authors.initials: E
authors.lastname: Leithe
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018031:Connexin 43; D003513:Cycloheximide / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D018031:Connexin 43; D003513:Cycloheximide; C526200:Smurf2 protein, rat; D044767:Ubiquitin-Protein Ligases; D013755:Tetradecanoylphorbol Acetate