Jacobsen Nicole L, Pontifex Tasha K, Langlais Paul R, Burt Janis M
Department of Physiology, University of Arizona, Tucson, AZ 85724, USA.
Department of Medicine, University of Arizona, Tucson, AZ 85724, USA.
Cancers (Basel). 2019 Feb 6;11(2):188. doi: 10.3390/cancers11020188.
Differential phosphorylation of the carboxyl-terminus of connexin 37 (Cx37-CT) regulates phenotypic switching between cell growth phenotypes (cell death, cell cycle arrest, proliferation). The specific phosphorylation events in the Cx37-CT that are necessary for these growth regulatory effects are currently unknown. Through the combined use of deletion and site specific (de)phospho-mimetic Cx37-CT mutants, our data suggest a phosphorylation-dependent interaction between the mid-tail (aa 273⁻317) and end-tail (aa 318⁻333) portions of the Cx37-CT that regulates cell survival. As detected by mass spectrometry, Cx37 was phosphorylated at serines 275, 321, and 328; phosphomimetic mutations of these sites resulted in cell death when expressed in rat insulinoma cells. Alanine substitution at S328, but not at S275 or S321, also triggered cell death. Cx37-S275D uniquely induced the death of only low density, non-contact forming cells, but neither hemichannel open probability nor channel conductance distinguished death-inducing mutants. As channel function is necessary for cell death, together the data suggest that the phosphorylation state of the Cx37-CT controls an intra-domain interaction within the CT that modifies channel function and induces cell death.
连接蛋白37（Cx37）羧基末端的差异磷酸化调节细胞生长表型（细胞死亡、细胞周期停滞、增殖）之间的表型转换。目前尚不清楚Cx37羧基末端中这些生长调节作用所必需的特定磷酸化事件。通过联合使用缺失型和位点特异性（去）磷酸化模拟Cx37羧基末端突变体，我们的数据表明Cx37羧基末端的中尾（氨基酸273⁻317）和尾端（氨基酸318⁻333）部分之间存在磷酸化依赖性相互作用，这种相互作用调节细胞存活。通过质谱检测，Cx37在丝氨酸275、321和328处发生磷酸化；这些位点的磷酸化模拟突变在大鼠胰岛素瘤细胞中表达时导致细胞死亡。S328处的丙氨酸取代而非S275或S321处的取代也引发细胞死亡。Cx37-S275D仅特异性诱导低密度、非接触形成细胞的死亡，但半通道开放概率和通道电导均无法区分诱导死亡的突变体。由于通道功能对于细胞死亡是必需的，这些数据共同表明Cx37羧基末端的磷酸化状态控制着羧基末端内的域内相互作用，这种相互作用改变通道功能并诱导细胞死亡。
