Mammalian class E Vps proteins, SBP1 and mVps2/CHMP2A, interact with and regulate the function of an AAA-ATPase SKD1/Nps4B
Mammalian class E Vps proteins, SBP1 and mVps2/CHMP2A, interact with and regulate the function of an AAA-ATPase SKD1/Nps4B
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DOI：
10.1242/jcs.01170
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发表时间：
2004-06-15
影响因子：
4
通讯作者：
Himeno, M
中科院分区：
文献类型：
--
作者：
Fujita, H;Umezuki, Y;Himeno, M
SKD1属于aaa - atp酶家族，是哺乳动物E类Vps（液泡蛋白分选）蛋白之一。先前我们已经报道过atp酶活性缺乏形式的SKD1（钾转运生长缺陷抑制因子）SKD1（E235Q）的过表达导致通过内体的膜转运的扰动；然而，SKD1作用背后的分子机制尚不清楚。通过酵母双杂交筛选，我们鉴定出两个skd1结合蛋白SBP1和mVps2，并将它们归类为哺乳动物E类Vps蛋白。SBP1与酿酒酵母（Saccharomyces cerevisiae）的Vta1p同源性为22.5%，后者最近被鉴定为与Vps4p结合的新型E类Vps蛋白。事实上，SBP1通过其c端区直接与SKD1结合（198-309）。内生的;SBP1只定位于细胞质，但它在表达SKD1（E235Q）的细胞中被重定向到异常的内体结构E235Q区。SKD1的atp酶活性调节含有SBP1的大型异聚寡聚蛋白复合物的膜结合和组装，SBP1可能参与通过核内体和溶酶体的膜运输。人SBP1的n端一半（1-157）与溶酶相互作用蛋白5相同，有趣的是，SKD1 atp酶活性显著影响溶酶蛋白的膜结合。SKD1-SBP1复合体与溶酶蛋白可能在内体膜运输中起作用。人类CHMP2A/BC-2的小鼠同源物mVps2的初级序列与酿酒酵母的Vps2p/Did4p/Chm2p的同源性为44.4%。mVps2也与SKD1相互作用，定位于E235Q区室。有趣的是，mVps2的n端线圈区域是E235Q区形成所必需的，但不是与SKD1结合所必需的。我们认为SBP1和mVps2都能调节哺乳动物细胞中SKD1的功能。
SKD1 belongs to the AAA-ATPase family and is one of the mammalian class E Vps (vacuolar protein sorting) proteins. Previously we have reported that the overexpression of an ATPase activity-deficient form of SKD1 (suppressor of potassium transport growth defect), SKD1(E235Q), leads the perturbation of membrane transport through endosomes; and lysosomes, however, the molecular mechanism behind the action of SKD1 is poorly understood. We have identified two SKD1-binding proteins, SBP1 and mVps2, by yeast two-hybrid screening and we assign them as mammalian class E Vps proteins. The primary sequence of SBP1 indicates 22.5% identity with that of Vta1p from Saccharomyces cerevisiae, which was recently identified as a novel class E Vps protein binding to Vps4p. In fact, SBP1 binds directly to SKD1 through its C-terminal region (198-309). Endogenous; SBP1 is exclusively localized to cytosol, however it is redirected to an aberrant endosomal structure, the E235Q compartment, in the cells expressing SKD1(E235Q). The ATPase activity of SKD1 regulates both the membrane association of, and assembly of, a large hetero-oligomer protein complex, containing SBP1, which is potentially involved in membrane transport through endosomes and lysosomes. The N-terminal half (1-157) of human SBP1 is identical to lyst-interacting protein 5 and intriguingly, SKD1 ATPase activity significantly influences the membrane association of lyst protein. The SKD1-SBP1 complex, together with lyst protein, may function in endosomal membrane transport. A primary sequence of mVps2, a mouse homologue of human CHMP2A/BC-2, indicates 44.4% identity with Vps2p/Did4p/Chm2p from Saccharomyces cerevisiae. mVps2 also interacts with SKD1 and is localized to the E235Q compartment. Intriguingly, the N-terminal coiled-coil region of mVps2 is required for the formation of the E235Q compartment but not for binding to SKD1. We propose that both SBP1 and mVps2 regulate SKD1 function in mammalian cells.