Taylor Samantha-Su Z, Jacobsen Nicole L, Pontifex Tasha K, Langlais Paul, Burt Janis M
College of Medicine, University of Arizona, Phoenix, AZ 85004, USA.
Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65211, USA.
J Cell Sci. 2020 Jun 18;133(12):jcs240721. doi: 10.1242/jcs.240721.
Connexin 37 (Cx37; protein product of ) 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.
连接蛋白37（Cx37； 的蛋白质产物）的表达以一种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，显著抑制大鼠胰岛素瘤（Rin）细胞的增殖。在Rin细胞中，诱导Cx37表达后生长会停滞，丝氨酸319（S319）经常发生磷酸化。在这里，我们表明，阻止该位点的磷酸化（丙氨酸替代；S319A）可消除Cx37的生长抑制作用，而模拟该位点的磷酸化（天冬氨酸替代；S319D）则增强了Cx37的生长抑制特性。与野生型Cx37（Cx37-WT）一样，Cx37-S319D的GJChs和半通道（HChs）更喜欢关闭状态，很少完全打开，且门控缓慢。相比之下，Cx37-S319A通道更喜欢开放状态，能完全打开且门控迅速。这些数据表明，Cx37蛋白中磷酸化依赖性的构象差异和通道功能是Cx37诱导的生长停滞与生长允许表型的基础。Cx37-WT和Cx37-S319D的GJChs和HChs的关闭状态有利于生长停滞，这表明导致细胞周期停滞的并非特定的通透分子，而是关闭的构象支持Cx37与导致生长停滞的生长调节蛋白相互作用。
