Sirnes Solveig, Kjenseth Ane, Leithe Edward, Rivedal Edgar
Department of Cancer Prevention, Institute for Cancer Research, Norwegian Radium Hospital, Montebello, Oslo, Norway.
Biochem Biophys Res Commun. 2009 Apr 24;382(1):41-5. doi: 10.1016/j.bbrc.2009.02.141. Epub 2009 Mar 1.
Gap junction channels are made of a family proteins called connexins. The best-studied type of connexin, Connexin43 (Cx43), is phosphorylated at several sites in its C-terminus. The tumor-promoting phorbol ester TPA strongly inhibits Cx43 gap junction channels. In this study we have investigated mechanisms involved in TPA-induced phosphorylation of Cx43 and inhibition of gap junction channels. The data show that TPA-induced inhibition of gap junction intercellular communication (GJIC) is dependent on both PKC and the MAP kinase pathway. The data suggest that PKC-induced activation of MAP kinase partly involves Src-independent trans-activation of the EGF receptor, and that TPA-induced shift in SDS-PAGE gel mobility of Cx43 is caused by MAP kinase phosphorylation, whereas phosphorylation of S368 by PKC does not alter gel migration of Cx43. We also show that TPA, in addition to phosphorylation of S368, also induces phosphorylation of S255 and S262, in a MAP kinase-dependent manner. The data add to our understanding of the molecular mechanisms involved in the interplay between signaling pathways in regulation of GJIC.
间隙连接通道由一类名为连接蛋白的蛋白质组成。研究最为深入的连接蛋白类型，即连接蛋白43（Cx43），在其C末端的多个位点发生磷酸化。促肿瘤的佛波酯TPA强烈抑制Cx43间隙连接通道。在本研究中，我们探究了TPA诱导Cx43磷酸化及抑制间隙连接通道所涉及的机制。数据表明，TPA诱导的间隙连接细胞间通讯（GJIC）抑制依赖于蛋白激酶C（PKC）和丝裂原活化蛋白激酶（MAP激酶）途径。数据提示，PKC诱导的MAP激酶活化部分涉及表皮生长因子（EGF）受体非Src依赖性的反式激活，并且TPA诱导的Cx43在十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）中的迁移率变化是由MAP激酶磷酸化引起的，而PKC对S368的磷酸化不会改变Cx43的凝胶迁移率。我们还表明，TPA除了使S368磷酸化外，还以MAP激酶依赖性方式诱导S255和S262磷酸化。这些数据增进了我们对GJIC调节中信号通路相互作用所涉及分子机制的理解。
