Constitutive and accelerated shedding of murine syndecan-1 is mediated by cleavage of its core protein at a specific juxtamembrane site.
Constitutive and accelerated shedding of murine syndecan-1 is mediated by cleavage of its core protein at a specific juxtamembrane site.
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DOI：
10.1021/bi050620i
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发表时间：
2005-09
期刊：
影响因子：
2.9
通讯作者：
Zihua Wang;M. Götte;M. Bernfield;O. Reizes
中科院分区：
文献类型：
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作者：
Zihua Wang;M. Götte;M. Bernfield;O. Reizes
Syndecan-1是一种发育调节的细胞表面硫酸乙酰肝素蛋白聚糖（HSPG）。它作为多种可溶性和不溶性配体的辅助受体发挥作用，并参与几种生物学过程，包括分化、细胞迁移、形态发生和最近的摄食行为。多配体蛋白聚糖-1的胞外结构域在被称为脱落的过程中响应于多种生理刺激物和应激而在质膜位点被金属蛋白酶-3（TIMP-3）敏感性金属蛋白酶的组织抑制剂蛋白水解切割。脱落将syndecan-1从膜结合的辅助受体转化为能够结合相同配体的可溶性效应物。我们发现用人CD 4氨基酸残基替换多配体蛋白聚糖-1胞膜氨基酸残基A243-S-Q-S-L247可以完全阻断PMA诱导的多配体蛋白聚糖-1胞外域脱落。此外，使用液相色谱-电喷雾电离质谱（LC-ESI-MS），我们确定了syndecan-1的蛋白水解切割位点的氨基酸A243和S244，产生的组成性和PMA诱导的脱落从小鼠NMuMG细胞。最后，我们表明，syndecan-1的基础裂解利用相同的在体内的网站在体外网站。事实上，正如所预测的，表达syndecan-1/CD 4 cDNA的转基因小鼠在体内不脱落syndecan-1胞外域。这些结果表明，相同的切割位点用于在体外从NMuMG和CHO细胞以及在体内的基础多配体蛋白聚糖-1胞外域脱落。
Syndecan-1 is a developmentally regulated cell surface heparan sulfate proteoglycan (HSPG). It functions as a coreceptor for a variety of soluble and insoluble ligands and is implicated in several biological processes, including differentiation, cell migration, morphogenesis, and recently feeding behavior. The extracellular domain of syndecan-1 is proteolytically cleaved at a juxtamembrane site by tissue inhibitor of metalloprotease-3 (TIMP-3)-sensitive metalloproteinases in response to a variety of physiological stimulators and stress in a process known as shedding. Shedding converts syndecan-1 from a membrane-bound coreceptor into a soluble effector capable of binding the same ligands. We found that replacing syndecan-1 juxtamembrane amino acid residues A243-S-Q-S-L247 with human CD4 amino acid residues can completely block PMA-induced syndecan-1 ectodomain shedding. Furthermore, using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS), we identified the proteolytic cleavage site of syndecan-1 as amino acids A243 and S244, generated by constitutive and PMA-induced shedding from murine NMuMG cells. Finally, we show that basal cleavage of syndecan-1 utilizes the same in vivo site as the in vitro site. Indeed, as predicted, transgenic mice expressing the syndecan-1/CD4 cDNA do not shed the syndecan-1 ectodomain in vivo. These results suggest that the same cleavage site is utilized for basal syndecan-1 ectodomain shedding both in vitro from NMuMG and CHO cells and in vivo.