Connexin 37 Regulation of Cell Proliferation Through Binding Interactions with Connexin 43 and 14-3-3σ

Abstract

Whereas Cx43 expression has no effect on proliferation of Rin cells, Cx37 exerts a potent growth suppressive effect on these cells. To determine how Cx37 suppresses growth and whether coexpression of Cx43 altered the suppressive effects of Cx37, two cell lines were created. 43tet/37 C4 cells constitutively express Cx43 and the tet-on transcription factor, which supports tetractycline inducible Cx37 expression in these cells. i43/i37 D6 cells constitutively express the tet-on transcription factor, which supports inducible expression of both connexins. The 43tet/37 C4 cells exhibit high Cx43:Cx37 expression ratio, whereas the i43/i37 D6 cells have a low Cx43:Cx37 expression ratio. In both cell lines, Cx37 and Cx43 appear (by reciprocal coimmunoprecipitation experiments) to form heteromeric channels. The proliferative properties of the co-expressing cell lines show that Cx37 growth suppression in Rin cells is relieved in a dose dependent manner by the presence of Cx43. In contrast, we demonstrate that 14-3-3σ may play a role in the growth suppressive mechanism of Cx37 in Rin cells as it is upregulated in cells expressing Cx37 and has the capability of binding to Cx37, presumably at the consensus binding motif in the C-terminus.