Chandrasekhar Kshama D, Bas Tuba, Kobertz William R
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
J Biol Chem. 2006 Dec 29;281(52):40015-23. doi: 10.1074/jbc.M604398200. Epub 2006 Oct 24.
KCNE peptides are a class of type I transmembrane beta subunits that assemble with and modulate the gating and ion conducting properties of a variety of voltage-gated K(+) channels. Accordingly, mutations that disrupt the assembly and trafficking of KCNE-K(+) channel complexes give rise to disease. The cellular mechanisms responsible for ensuring that KCNE peptides assemble with voltage-gated K(+) channels have yet to be elucidated. Using enzymatic deglycosylation, immunofluorescence, and quantitative cell surface labeling experiments, we show that KCNE1 peptides are retained in the early stages of the secretory pathway until they co-assemble with specific K(+) channel subunits; co-assembly mediates KCNE1 progression through the secretory pathway and results in cell surface expression. We also address an apparent discrepancy between our results and a previous study in human embryonic kidney cells, which showed wild type KCNE1 peptides can reach the plasma membrane without exogenously expressed K(+) channel subunits. By comparing KCNE1 trafficking in three cell lines, our data suggest that the errant KCNE1 trafficking observed in human embryonic kidney cells may be due, in part, to the presence of endogenous voltage-gated K(+) channels in these cells.
KCNE 肽是一类 I 型跨膜β亚基，它们与多种电压门控 K(+) 通道组装在一起，并调节其门控和离子传导特性。因此，破坏 KCNE-K(+) 通道复合物组装和运输的突变会导致疾病。负责确保 KCNE 肽与电压门控 K(+) 通道组装的细胞机制尚未阐明。通过酶促去糖基化、免疫荧光和定量细胞表面标记实验，我们表明 KCNE1 肽在分泌途径的早期阶段被保留，直到它们与特定的 K(+) 通道亚基共同组装；共同组装介导 KCNE1 通过分泌途径的进程并导致细胞表面表达。我们还解决了我们的结果与先前在人胚肾细胞中的一项研究之间的明显差异，该研究表明野生型 KCNE1 肽可以在没有外源表达的 K(+) 通道亚基的情况下到达质膜。通过比较三种细胞系中 KCNE1 的运输，我们的数据表明，在人胚肾细胞中观察到的错误的 KCNE1 运输可能部分归因于这些细胞中内源性电压门控 K(+) 通道的存在。
