MAL mediates apical transport of secretory proteins in polarized epithelial Madin-Darby canine kidney cells
MAL mediates apical transport of secretory proteins in polarized epithelial Madin-Darby canine kidney cells
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DOI：
10.1074/jbc.m106882200
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发表时间：
2001-12-28
影响因子：
4.8
通讯作者：
Alonso, MA
中科院分区：
文献类型：
--
作者：
Martín-Belmonte, F;Arvan, P;Alonso, MA
Mal蛋白脂是一种完整的膜蛋白，被认为是Madin-Darby犬肾(MDCK)细胞膜蛋白顶端分选的RAFT机械的组成部分。以前的研究表明，脂筏参与了外源性甲状腺球蛋白(TG)的运输，外源性甲状腺球蛋白(TG)是甲状腺上皮细胞的主要分泌蛋白，在MDCK细胞的顶面。我们检测了重组Tg和gp80/Clusterin的分泌，这是一种在Triton X-100不溶性木筏中未检测到的主要内源性分泌蛋白，以探讨MAL参与MDCK细胞结构性顶端分泌途径的作用。我们发现MAL耗竭损害了顶端TG的分泌，并导致其在高尔基体内积聚。胆固醇隔离，阻断了甘油三酯的顶端分泌，并没有改变木筏中ALAL的水平，但在甘油三酯进入木筏的近端形成了一个阻塞。内源性NUL的消除也抑制了gp80/Clusterin的顶端分泌。我们的结果表明，MAL在MDCK细胞内源性和外源性表达的顶端分泌蛋白的运输中都发挥了作用。
The MAL proteolipid is an integral membrane protein identified as a component of the raft machinery for apical sorting of membrane proteins in Madin-Darby canine kidney (MDCK) cells. Previous studies have implicated lipid rafts in the transport of exogenous thyroglobulin (Tg), the predominant secretory protein of thyroid epithelial cells, to the apical surface in MDCK cells. We have examined the secretion of recombinant Tg and gp80/clusterin, a major endogenous secretory protein not detected in Triton X-100 insoluble rafts, for the investigation of the involvement of MAL in the constitutive apical secretory pathway of MDCK cells. We show that MAL depletion impairs apical secretion of Tg and causes its accumulation in the Golgi. Cholesterol sequestration, which blocks apical secretion of Tg, did not alter the levels of ALAL in rafts but created a block proximal to Tg entrance into rafts. Apical secretion of gp80/ clusterin was also inhibited by elimination of endogenous NUL. Our results suggest a role for MAL in the transport of both endogenously and exogenously expressed apical secretory proteins in MDCK cells.