Role of the Vtc proteins in V-ATPase stability and membrane trafficking
Role of the Vtc proteins in V-ATPase stability and membrane trafficking
复制标题
DOI：
10.1242/jcs.00328
复制
发表时间：
2003-03-15
影响因子：
4
通讯作者：
Mayer, A
中科院分区：
文献类型：
--
作者：
Müller, O;Neumann, H;Mayer, A
Vtc蛋白与液泡H+- atp酶（V-ATPase）具有遗传和物理关系，影响液泡H+摄取，与v - atp酶的V-0区一样，是液泡膜融合的重要因素。vtc1Delta和vtc4Delta突变体液泡的H+摄取活性略有降低。这些缺陷可以从液泡融合中的Vtc功能中分离出来，表明Vtc蛋白在膜融合中具有直接作用。我们分析了它们在其他膜运输步骤和v - atp酶动力学中的作用。VTC基因的缺失并不妨碍内吞向液泡的运输。然而，在Deltavtc3细胞中，内质网到高尔基体运输和进一步运输到液泡被延迟。与此同时，Deltavtc3细胞的生长速度下降。Vtc突变不会干扰V-ATPase的组装和拆卸，但会影响与液泡相关的外周V-1亚基的数量。Deltavtc3液泡携带较多的V-1亚基，而Deltavtc1、Deltavtc2和Deltavtc4液泡携带较少。V-0亚基Vph1p在Deltavtc和野生型细胞体内的蛋白水解敏感性不同，证实了Vtc蛋白与体外观察到的V-ATPase的物理相互作用。我们认为Vtc蛋白影响V-0的构象。它们可能因此影响v - atp酶全酶的稳定性，并支持其V-0区在液泡膜融合中的功能。
Vtc proteins have genetic and physical relations with the vacuolar H+-ATPase (V-ATPase), influence vacuolar H+ uptake and, like the V-ATPase V-0 sectors, are important factors in vacuolar membrane fusion. Vacuoles from vtc1Delta and vtc4Delta mutants had slightly reduced H+-uptake activity. These defects could be separated from Vtc function in vacuole fusion, demonstrating that Vtc proteins have a direct role in membrane fusion. We analyzed their involvement in other membrane trafficking steps and in V-ATPase dynamics. Deletion of VTC genes did not impede endocytic trafficking to the vacuole. However, ER to Golgi trafficking and further transport to the vacuole was delayed in Deltavtc3 cells. In accordance with that, Deltavtc3 cells showed a reduced growth rate. Vtc mutations did not interfere with regulated assembly and disassembly of the V-ATPase, but they affected the number of peripheral V-1 subunits associated with the vacuoles. Deltavtc3 vacuoles carried significantly more V-1 subunits, whereas Deltavtc1, Deltavtc2 and Deltavtc4 had significantly less. The proteolytic sensitivity of the V-0 subunit Vph1p was different in Deltavtc and wild-type cells in vivo, corroborating the physical interaction of Vtc proteins with the V-ATPase observed in vitro. We suggest that Vtc proteins affect the conformation of V-0. They might thereby influence the stability of the V-ATPase holoenzyme and support the function of its V-0 sector in vacuolar membrane fusion.