Connexin 37 (Cx37; protein product of GJA4) expression profoundly suppresses proliferation of rat insulinoma (Rin) cells in a manner dependent on gap junction channel (GJCh) functionality and the presence and phosphorylation status of its C-terminus (CT). In Rin cells, growth is arrested upon induced Cx37 expression and serine 319 (S319) is frequently phosphorylated. Here, we show that preventing phosphorylation at this site (alanine substitution; S319A) relieved Cx37 of its growth-suppressive effect whereas mimicking phosphorylation at this site (aspartate substitution; S319D) enhanced the growth-suppressive properties of Cx37. Like wild-type Cx37 (Cx37-WT), Cx37-S319D GJChs and hemichannels (HChs) preferred the closed state, rarely opening fully, and gated slowly. In contrast, Cx37-S319A channels preferred open states, opened fully and gated rapidly. These data indicate that phosphorylation-dependent conformational differences in Cx37 protein and channel function underlie Cx37-induced growth arrest versus growth-permissive phenotypes. That the closed state of Cx37-WT and Cx37-S319D GJChs and HChs favors growth arrest suggests that rather than specific permeants mediating cell cycle arrest, the closed conformation instead supports interaction of Cx37 with growth regulatory proteins that result in growth arrest.

Connexin 37（Cx37； GJA4的蛋白质产物）表达以依赖于间隙连接通道（GJCh）功能及其 C 末端（CT）的存在和磷酸化状态的方式深刻抑制大鼠胰岛素瘤（Rin）细胞的增殖。在 Rin 细胞中，诱导的 Cx37 表达导致生长停滞，并且丝氨酸 319 (S319) 经常被磷酸化。在这里，我们表明，阻止该位点的磷酸化（丙氨酸取代；S319A）可以减轻 Cx37 的生长抑制作用，而模拟该位点的磷酸化（天冬氨酸取代；S319D）则增强了 Cx37 的生长抑制特性。与野生型 Cx37 (Cx37-WT) 一样，Cx37-S319D GJCh 和半通道 (HCh) 更喜欢关闭状态，很少完全打开，并且门控缓慢。相比之下，Cx37-S319A 通道首选开放状态，完全开放并快速门控。这些数据表明，Cx37 蛋白和通道功能中磷酸化依赖性构象差异是 Cx37 诱导的生长停滞与生长允许表型的基础。Cx37-WT 和 Cx37-S319D GJChs 和 HChs 的闭合状态有利于生长停滞，这表明闭合构象不是介导细胞周期停滞的特定渗透物，而是支持 Cx37 与生长调节蛋白的相互作用，从而导致生长停滞。