The tumor-suppressive function of Connexin43 in keratinocytes is mediated in part via interaction with caveolin-1.
Connexin43 (Cx43) is known to have tumor-suppressive effects, but the underlying mechanisms are still poorly understood. In keratinocytes, we previously showed that the COOH-terminal domain of Cx43 directly interacts with the tumor suppressor Cav-1. We now show that rat epidermal keratinocytes (REK) that are reduced in Cx43 present features of epithelial-to-mesenchymal transition and are more invasive than their control counterparts, whereas overexpression of Cx43 inhibited the 12-O-tetradecanoyl-phorbol-13-acetate (TPA)- and epidermal growth factor (EGF)-induced invasive properties. Carbenoxolone did not alter the inhibitory effect of Cx43 against TPA- and EGF-induced cell invasion, indicating the involvement of a gap junctional intercellular communication-independent mechanism. Interestingly, the association of Cx43 with Cav-1 was found to be reduced after TPA and EGF treatment. Accordingly, the colocalization of Cx43 with Cav-1 was diminished in cells from a human epidermal squamous cell carcinoma, as well as in sections from human keratinocyte tumors, suggesting that Cx43/Cav-1 interaction plays a protective role against keratinocyte transformation. As opposed to cells that overexpress Cx43-GFP, invasion could be induced in rat epidermal keratinocytes that overexpressed a GFP-tagged truncated mutant of Cx43 (Delta244-GFP) that we previously showed not to interact with Cav-1, as well as in cells that overexpressed Cx43-GFP but were reduced in Cav-1. Our data show that Cx43 possesses tumor-suppressive properties in keratinocytes and provide the first evidence that the Cx43/Cav-1 interaction is altered in keratinocyte transformation processes, as well as in human keratinocyte tumors, and that this association might play a role in Cx43-mediated tumor suppression.
Langlois
Stéphanie
S
Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada.
Cowan
Kyle N
KN
Shao
Qing
Q
Cowan
Bryce J
BJ
Laird
Dale W
DW
D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D015153:Blotting, Western; D002229:Carbenoxolone / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication; D049109:Cell Proliferation / Q000187:drug effects; D018031:Connexin 43 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions; D049452:Green Fluorescent Proteins; D006801:Humans; D047468:Immunoprecipitation; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009361:Neoplasm Invasiveness; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D000897:Anti-Ulcer Agents; D002273:Carcinogens; D051242:Caveolin 1; D018031:Connexin 43; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; D049452:Green Fluorescent Proteins; D004815:Epidermal Growth Factor; D002229:Carbenoxolone; D013755:Tetradecanoylphorbol Acetate