SELECTIVELY AMPLIFIED EXPRESSION OF AN ISOFORM OF THE VACUOLAR H+-ATPASE 56-KILODALTON SUBUNIT IN RENAL INTERCALATED CELLS
SELECTIVELY AMPLIFIED EXPRESSION OF AN ISOFORM OF THE VACUOLAR H+-ATPASE 56-KILODALTON SUBUNIT IN RENAL INTERCALATED CELLS
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DOI：
10.1073/pnas.89.8.3541
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发表时间：
1992-04-15
影响因子：
11.1
通讯作者：
GLUCK, S
中科院分区：
文献类型：
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作者：
NELSON, RD;GUO, XL;GLUCK, S
肾集合管的闰细胞专门用于生理调节的质子转运。在这些细胞中，液泡H+-ATP酶在质膜上以极化分布的巨大水平表达，使其能够在跨上皮H+转运中发挥作用。相比之下，在大多数真核细胞中，液泡H+-ATP酶主要存在于细胞内区室中以影响液泡酸化。为了研究闰细胞中质子泵选择性扩增的基础，我们分离并测序了H+-ATP酶的几乎等于56 kDa亚基的两种亚型的cDNA克隆，并研究了它们在各种组织中的表达。预测的氨基酸序列的异构体是高度保守的内部区域，但分歧的氨基和羧基末端。仅在肾皮质和髓质中检测到与一种亚型（“肾”亚型）的cDNA探针的mRNA杂交，而在肾和其他组织中发现与几乎等于56-kDa亚基的另一种亚型和与H+-ATP酶31-kDa亚基的mRNA杂交。用肾脏亚型特异性抗体对大鼠肾脏进行免疫细胞化学分析，发现仅在闰细胞中有强烈染色。近端小管和粗的升支无染色，其中H +-ATP酶用H+-ATP酶31-kDa亚基的单克隆抗体检测。限制于特定细胞类型的液泡H+-ATP酶的一个亚基的同种型的特异性扩增的这个例子表明，几乎等于56-kDa亚基的肾同种型的选择性表达可以赋予肾闰细胞中的液泡H+-ATP酶的扩增能力和其他专门功能。
The intercalated cells of the kidney collecting duct are specialized for physiologically regulated proton transport. In these cells, a vacuolar H+-ATPase is expressed at enormous levels in a polarized distribution on the plasma membrane, enabling it to serve in transepithelial H+ transport. In contrast, in most eukaryotic cells, vacuolar H+-ATPases reside principally in intracellular compartments to effect vacuolar acidification. To investigate the basis for the selective amplification of the proton pump in intercalated cells, we isolated and sequenced cDNA clones for two isoforms of the almost-equal-to 56-kDa subunit of the H+-ATPase and examined their expression in various tissues. The predicted amino acid sequence of the isoforms was highly conserved in the internal region but diverged in the amino and carboxyl termini. mRNA hybridization to a cDNA probe for one isoform (the "kidney" isoform) was detected only in kidney cortex and medulla, whereas mRNA hybridization to the other isoform of the almost-equal-to 56-kDa subunit and to the H+-ATPase 31-kDa subunit was found in the kidney and other tissues. Immunocytochemistry of rat kidney with an antibody specific to the kidney isoform revealed intense staining only in the intercalated cells. Staining was absent from proximal tubule and thick ascending limb, where H+-ATPase was detected with a monoclonal antibody to the 31-kDa subunit of the H+-ATPase. This example of specific amplification of an isoform of one subunit of the vacuolar H+-ATPase being limited to a specific cell type suggests that the selective expression of the kidney isoform of the almost-equal-to 56-kDa subunit may confer the capacity for amplification and other specialized functions of the vacuolar H+-ATPase in the renal intercalated cell.