N-terminal processing is essential for release of epithin, a mouse type II membrane serine protease
N-terminal processing is essential for release of epithin, a mouse type II membrane serine protease
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DOI：
10.1074/jbc.m107059200
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发表时间：
2001-11-30
影响因子：
4.8
通讯作者：
Park, D
中科院分区：
文献类型：
--
作者：
Cho, EG;Kim, MG;Park, D
Epithin最初被鉴定为小鼠II型膜丝氨酸蛋白酶。据报道，其人同源膜型丝氨酸蛋白酶1 (MT-SP1)/基质酶定位于质膜上。此外，从人母乳和乳腺癌细胞条件培养基中分离出可溶性基质酶。在本文中，我们报告了一种似乎是需要的卵磷脂释放的加工机制。CHO-K1或COS7细胞转染单个全长上皮磷脂cDNA后，在细胞裂解物中产生两种不同大小的蛋白，分别为110和92 kDa。92-kDa是110-kDa的n端截断形式，是培养基中唯一检测到的形式。在细胞表面也发现了92kda的上皮蛋白，它被n端片段锚定。体内细胞标记实验结果表明，110-kDa的上皮蛋白可快速加工成92-kDa的上皮蛋白。通过定点诱变实验，我们确定了磷脂中GSVIA序列的Gly（149）是蛋白质加工和释放所必需的。这些结果表明，磷脂在Gly149的n端加工是蛋白质释放的必要前提步骤。
Epithin was originally identified as a mouse type II membrane serine protease. Its human orthologue membrane type-serine protease 1 (MT-SP1)/matriptase has been reported to be localized on the plasma membrane. In addition, soluble forms of matriptase were isolated from human breast milk and breast cancer cell-conditioned medium. In this paper, we report a processing mechanism that appears to be required for the release of epithin. CHO-K1 or COS7 cells transfected with single full-length epithin cDNA generated two different-sized proteins in cell lysates, 110 and 92 kDa. The 92-kDa epithin was found to be an N-terminally truncated form of the 110-kDa epithin, and it was the only form detected in the culture medium. The 92-kDa epithin was also found on the cell surface, where it was anchored by the N-terminal fragment. The results of in vivo cell labeling experiments indicate that the 110-kDa epithin is rapidly processed to the 92-kDa epithin. Using site-directed mutagenesis experiments, we identified Gly(149) of the GSVIA sequence in epithin as required for the processing and release of the protein. These results suggest that N-terminal processing of epithin at Gly149 is a necessary prerequisite step for release of the protein.