Brown D, Breton S
Renal Unit and Program in Membrane Biology, Massachusetts General Hospital, Department of Pathology, Harvard Medical School, Boston, MA 02129, USA.
J Exp Biol. 2000 Jan;203(Pt 1):137-45. doi: 10.1242/jeb.203.1.137.
Many vertebrate transporting epithelia contain characteristic 'mitochondria-rich' cells that express high levels of a vacuolar proton-pumping ATPase (H(+)V-ATPase) on their plasma membrane and on intracellular vesicles. In the kidney cortex, A-cells and B-cells are involved in proton secretion and bicarbonate secretion, respectively, in the distal nephron and collecting duct. A-cells have an H(+)V-ATPase on their apical plasma membrane and on intracellular vesicles, whereas the cellular location of the H(+)V-ATPase can be apical, basolateral, bipolar or diffuse in B-cells. The rat epididymis and vas deferens also contain a distinct population of H(+)V-ATPase-rich epithelial cells. These cells are involved in generating a low luminal pH, which is involved in sperm maturation and in maintaining sperm in an immotile state during their passage through the epididymis and vas deferens. In both kidney and reproductive tract, H(+)V-ATPase-rich cells have a high rate of apical membrane recycling. H(+)V-ATPase molecules are transported between the cell surface and the cytoplasm in vesicles that have a well-defined 'coat' structure formed of the peripheral V(1) subunits of the H(+)V-ATPase. In addition, we propose that B-type intercalated cells have a transcytotic pathway that enables them to shuttle H(+)V-ATPase molecules from apical to basolateral plasma membrane domains. This hypothesis is supported by data showing that A-cells and B-cells have different intracellular trafficking pathways for LGP120, a lysosomal glycoprotein. LGP120 was found both on the basolateral plasma membrane and in lysosomes in B-cells, whereas no LGP120 was detectable in the plasma membrane of A-cells. We propose that the 'polarity reversal' of the H(+)V-ATPase in B-intercalated cells is mediated by a physiologically regulated transcytotic pathway that may be similar to that existing in some other cell types.
许多脊椎动物的转运上皮细胞含有特征性的“富含线粒体”细胞，这些细胞在其质膜和细胞内囊泡上高水平表达一种液泡质子泵ATP酶（H(+)V-ATP酶）。在肾皮质中，A细胞和B细胞分别参与远端肾单位和集合管中的质子分泌和碳酸氢盐分泌。A细胞在其顶端质膜和细胞内囊泡上有H(+)V-ATP酶，而H(+)V-ATP酶在B细胞中的细胞定位可以是顶端、基底外侧、双极或弥散性的。大鼠附睾和输精管也含有一群独特的富含H(+)V-ATP酶的上皮细胞。这些细胞参与产生低管腔pH值，这与精子成熟以及精子在通过附睾和输精管过程中维持静止状态有关。在肾脏和生殖道中，富含H(+)V-ATP酶的细胞具有较高的顶端膜循环率。H(+)V-ATP酶分子在细胞表面和细胞质之间通过由H(+)V-ATP酶的外周V(1)亚基形成的具有明确“衣被”结构的囊泡进行转运。此外，我们提出B型闰细胞有一条转胞吞途径，使它们能够将H(+)V-ATP酶分子从顶端质膜结构域穿梭到基底外侧质膜结构域。这一假说得到了数据支持，这些数据表明A细胞和B细胞对溶酶体糖蛋白LGP120有不同的细胞内运输途径。在B细胞的基底外侧质膜和溶酶体中都发现了LGP120，而在A细胞的质膜中未检测到LGP120。我们提出B型闰细胞中H(+)V-ATP酶的“极性反转”是由一种生理调节的转胞吞途径介导的，该途径可能与其他一些细胞类型中存在的途径相似。
