Regulatory mechanisms of CIC chloride channels by protein-protein interaction

(1)ClC-2通道的C末端被M期特异性细胞周期蛋白依赖性蛋白激酶p34；/cdc2/Cyclin B直接磷酸化，并被蛋白磷酸酶1去磷酸化，蛋白-蛋白相互作用在其中起着关键作用。在非洲爪哇卵母细胞中表达的ClC-2通道被磷酸化抑制，被去磷酸化激活。(2)Western印迹分析和免疫细胞化学显示，ClC-2通道蛋白在M期分裂的细胞中表达，并在细胞分裂后迅速消失。PEST序列是通过泛素化的短寿命蛋白的标志，并且在CLC-2的C末端存在多个PEST序列。P34；lt；cdc2&gt；/Cyclin B使ClC-2的丝氨酸磷酸化，触发ClC-2通道泛素化，这突显了M期特异性泛素化和ClC-2通道蛋白的降解。(3)ClC-3B是一种氯通道，主要在上皮细胞表达，定位于其微绒毛。ClC-3B与上皮特异性PDZ蛋白EBP50相互作用，从而与囊性纤维化基因产物囊性纤维化跨膜电导调节因子(CFTR)相互作用。CLC-3B氯通道是在CFTR存在的情况下被蛋白激酶A激活的，在跨上皮细胞的离子转运中起着重要的作用。

(1) The C-terminus of ClC-2 channel is directly phosphorylated by M phase-specific cyclin-dependent kinase, p34^<cdc2>/cyclin B, and de-phosphorylated by protein phosphatase 1, for which protein-protein interaction plays a crucial role. ClC-2 channel expressed in Xenopus oocytes is inhibited by phosphorylation and activated by dephosphorylation.(2) Western blot analysis and immunocytochemistry revealed that ClC-2 channel protein is expressed in dividing cells of the M phase of cell cycle, and promptly disappears after cell division. The PEST sequence is a signature of short-lived proteins via ubiquitination, and multiple PEST sequences are present in the C-terminus of ClC-2. Phosphorylation of ^<632>Ser of ClC-2 by p34^<cdc2>/cyclin B triggers ClC-2 channel ubiquitination, which underlines M phase-specific ubiquitination and degradation of ClC-2 channel protein.(3) ClC-3B is a chloride channel expressed predominantly in epithelial cells and is localized in its microvilli. ClC-3B interacts With EBP50, an epithelia-specific PDZ-containing protein, and thereby interacts with cystic fibrosis transmembrane conductance regulator (CFTR), a product of cystic fibrosis gene. ClC-3B chloride channel is activated by protein kinase A in the presence of CFTR, and is important in ionic transport across the epithelia.