Brown D, Sabolic I, Gluck S
Renal Unit, Massachusetts General Hospital.
J Exp Biol. 1992 Nov;172:231-43. doi: 10.1242/jeb.172.1.231.
The membrane-associated V-ATPase that plays an important role in the regulation of acid-base balance by the kidney is a multisubunit enzyme that is densely packed into specialized membrane domains in intercalated cells. Intercalated cells can be separated into at least two subtypes, A-cells and B-cells, based on their morphological features, the distribution of V-ATPase, and the presence or absence of a basolateral chloride/bicarbonate anion exchanger (AE1) exclusively in B-cells. A-cells secrete protons into the tubule lumen, whereas B-cells secrete bicarbonate. The relative amounts of V-ATPase and AE1 in the plasma membranes of A- and B-cells are modulated under different acid-base conditions and provide a sensitive means by which urinary acidification can be controlled. The mechanisms governing the movement of acid-base transporting proteins between intracellular vesicles and the plasma membrane are under investigation. The microtubular apparatus of the cell is involved in maintaining both apical and basolateral polarity of the enzyme, and different isoforms of V-ATPase subunits may also be involved in the selective targeting of V-ATPase to different membrane domains.
膜相关V-ATP酶在肾脏酸碱平衡调节中起重要作用，它是一种多亚基酶，密集地包装在闰细胞的特殊膜结构域中。根据形态特征、V-ATP酶的分布以及仅在B细胞中存在的基底外侧氯/碳酸氢根阴离子交换体（AE1）的有无，闰细胞可分为至少两种亚型，即A型细胞和B型细胞。A型细胞向肾小管管腔分泌质子，而B型细胞分泌碳酸氢根。在不同的酸碱条件下，A型和B型细胞质膜中V-ATP酶和AE1的相对含量会发生调节，这提供了一种控制尿液酸化的敏感方式。细胞内囊泡与质膜之间酸碱转运蛋白的移动机制正在研究中。细胞的微管装置参与维持该酶的顶端和基底外侧极性，V-ATP酶亚基的不同同工型也可能参与V-ATP酶向不同膜结构域的选择性靶向。
