Regulation of vacuolar proton-translocating ATPase activity and assembly by extracellular pH.
Regulation of vacuolar proton-translocating ATPase activity and assembly by extracellular pH.
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DOI：
10.1074/jbc.m110.110122
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发表时间：
2010-07-30
期刊：
影响因子：
--
通讯作者：
Kane, Patricia M
中科院分区：
文献类型：
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作者：
Diakov, Theodore T;Kane, Patricia M
极性质子转运ATP酶（V-ATP酶）负责所有真核细胞中的细胞器酸化。已知响应于葡萄糖剥夺通过可逆分解调节的酵母V-ATP酶，最近报道也通过细胞外pH调节（Padilla-Lopez，S.，和皮尔斯，D. A.（2006）J.Biol.Chem.281，10273-10280）。与这些结果相一致，我们发现高57%的V-ATP酶活性在细胞生长后分离的液泡在胞外pH值为7比生长后在pH值为5的基本培养基。值得注意的是，在这些条件下，V-ATP酶也变得对可逆分解很不敏感，在葡萄糖剥夺期间维持低液泡pH和高水平的V（1）亚基组装、ATP酶活性和质子泵送。在这些条件下，细胞溶质的pH值是恒定的，表明缺乏可逆的拆卸是不是改变细胞溶质pH值的反应。我们建议，当空泡酸化的替代机制不可用时，保持V-ATP酶活性成为一个优先事项，和泵不下调响应能量限制。这些结果还表明，综合pH值和代谢输入决定的最终组装状态和活性的V-ATP酶。
Vacuolar proton-translocating ATPases (V-ATPases) are responsible for organelle acidification in all eukaryotic cells. The yeast V-ATPase, known to be regulated by reversible disassembly in response to glucose deprivation, was recently reported to be regulated by extracellular pH as well (Padilla-Lopez, S., and Pearce, D. A. (2006) J. Biol. Chem. 281, 10273-10280). Consistent with those results, we find 57% higher V-ATPase activity in vacuoles isolated after cell growth at extracellular pH of 7 than after growth at pH 5 in minimal medium. Remarkably, under these conditions, the V-ATPase also becomes largely insensitive to reversible disassembly, maintaining a low vacuolar pH and high levels of V(1) subunit assembly, ATPase activity, and proton pumping during glucose deprivation. Cytosolic pH is constant under these conditions, indicating that the lack of reversible disassembly is not a response to altered cytosolic pH. We propose that when alternative mechanisms of vacuolar acidification are not available, maintaining V-ATPase activity becomes a priority, and the pump is not down-regulated in response to energy limitation. These results also suggest that integrated pH and metabolic inputs determine the final assembly state and activity of the V-ATPase.