MAL decreases the internalization of the aquaporin-2 water channel
MAL decreases the internalization of the aquaporin-2 water channel
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DOI：
10.1073/pnas.0708023104
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发表时间：
2007-10-16
影响因子：
11.1
通讯作者：
Caplan, Michael J.
中科院分区：
文献类型：
--
作者：
Kamsteeg, Erik-Jan;Duffield, Amy S.;Caplan, Michael J.
体内水分的稳态主要依赖于肾脏集合管上皮细胞水通道蛋白2（AQP 2）的运输。几种类型的翻译后修饰显然参与控制细胞内囊泡和顶端质膜之间的AQP 2的分布。然而，很少有人知道，关于蛋白质的相互作用，这些细胞器之间的AQP 2的运输管理。MAL是一种抗洗涤剂的膜相关蛋白，与顶端分选事件有关。因此，我们想知道MAL是否在胞内囊泡和顶端表面之间的AQP 2调节运输中起作用。我们发现，AQP 2和MAL共表达于肾集合管上皮细胞。这两种蛋白质相互作用，无论是在天然肾脏中，还是在培养细胞中通过转染表达。AQP 2的S256-磷酸化形式似乎比在此丝氨酸处未磷酸化的水通道蛋白更广泛地与MAL相互作用。我们发现MAL不参与LLC-PK 1肾上皮细胞的耐洗涤剂膜缔合或AQP 2的顶端递送。相反，MAL增加了S256磷酸化和AQP 2的顶端表面表达。此外，内化实验表明，MAL诱导AQP 2的表面表达减弱其内化。因此，MAL参与顶端膜蛋白的细胞表面保留可能在调节转运上皮细胞的吸收和分泌中发挥重要作用。
Body water homeostasis depends critically on the hormonally regulated trafficking of aquaporin-2 (AQP2) water channels in renal collecting duct epithelial cells. Several types of posttranslational modifications are clearly involved in controlling the distribution of AQP2 between intracellular vesicles and the apical plasma membrane. Little is known, however, about the protein interactions that govern the trafficking of AQP2 between these organelles. MAL is a detergent-resistant membrane-associated protein implicated in apical sorting events. We wondered, therefore, whether MAL plays a role in the regulated trafficking of AQP2 between intracellular vesicles and the apical surface. We find that AQP2 and MAL are coexpressed in epithelial cells of the kidney collecting duct. These two proteins interact, both in the native kidney and when expressed by transfection in cultured cells. The S256-phosphorylated form of AQP2 appears to interact more extensively with MAL than does the water channel protein not phosphorylated at this serine. We find that MAL is not involved in detergent-resistant membrane association or apical delivery of AQP2 in LLC-PK1 renal epithelial cells. Instead, MAL increases the S256 phosphorylation and apical surface expression of AQP2. Furthermore, internalization experiments show that MAL induces surface expression of AQP2 by attenuating its internalization. Thus, the involvement of MAL in the cell surface retention of apical membrane proteins could play an important role in regulated absorption and secretion in transporting epithelia.