Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans
Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans
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DOI：
10.1152/ajpcell.00284.2009
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发表时间：
2009-11-01
影响因子：
5.5
通讯作者：
Nehrke, Keith
中科院分区：
文献类型：
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作者：
Allman, Erik;Johnson, David;Nehrke, Keith
Allman E，Johnson D，Nehrke K.丢失顶端V-ATPase a亚单位VHA-6可防止线虫在节律行为中肠腔的酸化。Am J Physiol Cell Physiol 297：C1071-C1081,2009。2009年9月9日首次出版；doi：10.1152/ajpcell.00284.2009。-在秀丽线虫中，肠道pH的波动有助于有节奏的排便行为，但促进质子运动的酸碱运输机制尚不清楚。在这里，我们证明了VHA-6，一个肠道特异的H+-K+-ATPase复合体(V-ATPase)的α亚基，位于肠上皮细胞的顶膜上，是肠腔酸化所必需的。VHA-6基因的破坏导致早期发育停滞；这种停滞表型可以通过表达荧光标记的VHA-6转基因来补充。为了研究VHA-6在幼虫pH动态平衡中的作用，我们使用了胚胎后单代RNA干扰来部分降低功能。我们证明，无法完全酸化肠腔与肠道上皮细胞的pH恢复缺陷相一致，这表明VHA-6对于排便后的质子泵是必不可少的。此外，肠道二肽积累和脂肪储存因VHA-6的丢失而受到影响，这表明管腔酸化促进了蠕虫和哺乳动物的营养吸收。由于VHA-6突变体和对照之间不能区分酸化的细胞内小泡和自发荧光储存颗粒，营养限制表型可能是由于质膜V-ATPase活性的特异性丧失所致。这些数据为质子泵驱动的酸化建立了一个简单的成因模型。由于蠕虫的排便时间间隔为45-S，该模型提供了一个在短时间尺度上研究V-ATPase活性的急性调节的机会，并可能对酸消化性疾病的替代治疗方法的研究有用。
Allman E, Johnson D, Nehrke K. Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans. Am J Physiol Cell Physiol 297: C1071-C1081, 2009. First published September 9, 2009; doi:10.1152/ajpcell.00284.2009.-In Caenorhabditis elegans, oscillations of intestinal pH contribute to the rhythmic defecation behavior, but the acid-base transport mechanisms that facilitate proton movement are not well understood. Here, we demonstrate that VHA-6, an intestine-specific a-subunit of the H+-K+-ATPase complex (V-ATPase), resides in the apical membrane of the intestinal epithelial cells and is required for luminal acidification. Disruption of the vha-6 gene led to early developmental arrest; the arrest phenotype could be complemented by expression of a fluorescently labeled vha-6 transgene. To study the contribution of vha-6 to pH homeostasis in larval worms, we used a partial reduction of function through postembryonic single-generation RNA interference. We demonstrate that the inability to fully acidify the intestinal lumen coincides with a defect in pH recovery of the intestinal epithelial cells, suggesting that VHA-6 is essential for proton pumping following defecation. Moreover, intestinal dipeptide accumulation and fat storage are compromised by the loss of VHA-6, suggesting that luminal acidification promotes nutrient uptake in worms, as well as in mammals. Since acidified intracellular vesicles and autofluorescent storage granules are indistinguishable between the vha-6 mutant and controls, it is likely that the nutrient-restricted phenotype is due to a loss of plasma membrane V-ATPase activity specifically. These data establish a simple genetic model for proton pump-driven acidification. Since defecation occurs at 45-s intervals in worms, this model represents an opportunity to study acute regulation of V-ATPase activity on a short time scale and may be useful in the study of alternative treatments for acid-peptic disorders.