Department of Biochemistry and Molecular Biology.
Department of Biochemistry and Molecular Biology; Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198.
J Biol Chem. 2019 Jan 4;294(1):341-350. doi: 10.1074/jbc.RA118.003883. Epub 2018 Nov 6.
Gap junctions are intercellular conduits that permit the passage of ions, small metabolites, and signaling molecules between cells. Connexin32 (Cx32) is a major gap junction protein in the liver and brain. Phosphorylation is integral to regulating connexin assembly, degradation, and electrical and metabolic coupling, as well as to interactions with molecular partners. Cx32 contains two intracellular tyrosine residues, and tyrosine phosphorylation of Cx32 has been detected after activation of the epidermal growth factor receptor; however, the specific tyrosine residue and the functional implication of this phosphorylation remain unknown. To address the limited available information on Cx32 regulation by tyrosine kinases, here we used the Cx32 C-terminal (CT) domain in an kinase-screening assay, which identified ephrin (Eph) receptor family members as tyrosine kinases that phosphorylate Cx32. We found that EphB1 and EphA1 phosphorylate the Cx32CT domain residue Tyr Unlike for Cx43, the tyrosine phosphorylation of the Cx32CT increased gap junction intercellular communication. We also demonstrated that T-cell protein-tyrosine phosphatase dephosphorylates pTyr The data presented above along with additional examples throughout the literature of gap junction regulation by kinases, indicate that one cannot extrapolate the effect of a kinase on one connexin to another.
缝隙连接是细胞间的通道，允许离子、小分子代谢物和信号分子在细胞间传递。连接蛋白 32（Cx32）是肝脏和大脑中主要的缝隙连接蛋白。磷酸化是调节连接蛋白组装、降解以及电和代谢偶联的重要因素，也是与分子伴侣相互作用的重要因素。Cx32 含有两个细胞内酪氨酸残基，表皮生长因子受体激活后检测到 Cx32 的酪氨酸磷酸化；然而，这种磷酸化的特定酪氨酸残基和功能意义仍然未知。为了研究酪氨酸激酶对 Cx32 调节的有限信息，我们在这里使用了连接蛋白 32 C 端（CT）结构域进行激酶筛选分析，该分析鉴定出 Ephrin（Eph）受体家族成员为磷酸化 Cx32 的酪氨酸激酶。我们发现 EphB1 和 EphA1 磷酸化 Cx32CT 结构域残基 Tyr 与 Cx43 不同，Cx32CT 的酪氨酸磷酸化增加了缝隙连接细胞间通讯。我们还证明了 T 细胞蛋白酪氨酸磷酸酶去磷酸化 pTyr 以上数据以及文献中关于激酶调节缝隙连接的其他例子表明，不能将一种激酶对一种连接蛋白的影响推断到另一种连接蛋白上。
