Posttranslational processing of secretory component in the rat jejunum by a brush border metalloprotease.
Posttranslational processing of secretory component in the rat jejunum by a brush border metalloprotease.
复制标题
刷状缘金属蛋白酶对大鼠空肠分泌成分的翻译后加工。
DOI：
10.1172/jci112510
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Kloppel,TM
中科院分区：
文献类型：
--
作者：
Ahnen,DJ;Singleton,JR;Hoops,TC;Kloppel,TM
分泌成分（SC）是一种糖蛋白，介导聚合免疫球蛋白进入外部分泌物的跨细胞转运。SC作为一种跨膜蛋白被合成并插入上皮细胞和肝细胞的质膜中，作为聚合免疫球蛋白的受体。SC在分泌到外部液体之前被翻译后裂解成可溶性蛋白。在大鼠空肠中，我们观察到SC的主要膜和可溶性形式的分子量都比肝脏形式的糖蛋白小10,000-20,000。因此，我们着手确定这两种组织之间SC大小差异的原因。空肠SC较小的大小不是由于胰腺蛋白酶的作用或不同的糖基化，而是由于空肠刷状边缘蛋白酶的蛋白质水解。该蛋白酶具有金属蛋白酶的特征，其最适pH约为5。它作为一个完整的膜成分存在于空肠、回肠和肾小管刷边界。当蛋白酶在体内被抑制时，部分阻止了空肠分泌成分向较小尺寸的转化。因此，在大鼠空肠中，SC经历了两个翻译后蛋白水解事件：膜分泌成分转化为可溶性形式，可溶性SC通过先前描述的刷状边界蛋白酶转化为更小的尺寸。图片
Secretory component (SC) is a glycoprotein that mediates the transcellular transport of polymeric immunoglobulins into external secretions. SC is synthesized and inserted into the plasma membrane of epithelial cells and hepatocytes as a transmembrane protein, where it serves as a receptor for polymeric immunoglobulins. SC is posttranslationally cleaved to a soluble protein before secretion into external fluids. In the rat jejunum, we observed that the molecular weights of both the major membrane and soluble forms of SC were 10,000-20,000 smaller than the comparable hepatic forms of the glycoprotein. We therefore set out to determine the reason for the differences in size of SC between these two tissues. The smaller size of jejunal SC was not due to the action of pancreatic proteases or differential glycosylation but was due to proteolysis by a jejunal brush border protease. The protease was characterized as a metalloprotease, with a pH optimum of approximately 5. It is present in jejunal, ileal, and renal tubular brush borders as an integral membrane constituent. When the protease was inhibited in vivo, conversion of jejunal secretory component to the smaller size was partially prevented. Thus, in the rat jejunum, SC undergoes two posttranslational proteolytic events: conversion of membrane secretory component to the soluble form and conversion of soluble SC to a smaller size by a previously undescribed brush border protease.Images