Regulation of connexin-43-mediated growth inhibition by a phosphorylatable amino-acid is independent of gap junction-forming ability.
The ability of the gap junction phosphoprotein connexin-43 (Cx43) to inhibit DNA synthesis in primary cardiomyocytes is regulated by serine (S) 262, a protein kinase C phosphorylation site that also affects metabolic coupling. We have now examined if the S262-regulated growth suppression is operating in transformed cells and if so whether it depends on gap junction channel forming ability. Serine 262 became phosphorylated in response to protein kinase C stimulation in HEK293 cells transiently expressing either Cx43 or the non-channel-forming carboxy-terminal tail of Cx43 (Cx43CT). Expression of either wild type Cx43 or Cx43CT inhibited DNA synthesis, as did their mutated versions simulating lack of phosphorylation by carrying an S262-to-alanine substitution. The ability to inhibit DNA synthesis was eliminated when expressing mutated versions of either Cx43 or Cx43CT simulating constitutive phosphorylation by carrying an S262-to-aspartate substitution. We conclude that S262 phosphorylation cancels growth inhibition by Cx43 independently of channel-forming ability.
Dang
Xitong
X
Department of Human Anatomy and Cell Sciences and Physiology, University of Manitoba, Winnipeg, R2H 2A6, Canada.
Jeyaraman
Madhumathy
M
Kardami
Elissavet
E
D049109:Cell Proliferation; D002478:Cells, Cultured; D018031:Connexin 43 / Q000737:chemistry / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis; D017629:Gap Junctions / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism*
D018031:Connexin 43; D010768:Phosphoserine; D004247:DNA