Sar1-dependent trafficking of the human calcium receptor to the cell surface.
Sar1-dependent trafficking of the human calcium receptor to the cell surface.
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DOI：
10.1016/j.bbrc.2010.05.014
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发表时间：
2010-06-11
影响因子：
3.1
通讯作者：
Ray, Kausik
中科院分区：
文献类型：
--
作者：
Zhuang, Xiaolei;Chowdhury, Shoaib;Northup, John K.;Ray, Kausik
人钙受体(HCAR)离开内质网(ER)进行细胞表面转运的分子机制尚不清楚。我们研究了Sar1小GTP结合蛋白在Hcar细胞表面转运中的作用。用组成活性的Sar1H79G突变体破坏内源性Sar1的功能，或者使用小干扰RNA耗尽Sar1H79G，减弱HCAR的细胞表面表达。受体羧基尾端的几个推测的双酸性ER输出基序的突变显示，细胞表面表达没有明显的缺陷。缺少大部分羧基末端序列或所有胞内结构域的截短突变体在稳定状态下也没有表现出细胞表面表达的损害。只含有大的氨基末端细胞外配体结合域(ECD)的截短受体被分泌到培养基中，Sar1H79G抑制这种分泌。分子间二硫键二聚所必需的半胱氨酸突变为丝氨酸或N-糖基化的四个天冬酰胺突变为丙氨酸的ECD受体变异体也干扰了分泌，表明正确的ECD构象对该受体的前向运输至关重要。
The molecular mechanisms underlying the exit from the endoplasmic reticulum (ER) for cell surface trafficking of the human calcium receptor (hCaR) remain poorly understood. We investigated the role of the Sar1 small GTP-binding protein in cell surface transport of the hCaR. Disruptions of endogenous Sar1 function with the constitutively active Sar1H79G mutant or depletion using small interfering RNA, attenuates cell surface expression of the hCaR. Mutation of several putative di-acidic ER export motifs in the carboxyl-tail of the receptor revealed no apparent defect in cell surface expression. Truncated mutants lacking most of the carboxyl-terminal sequences or all intracellular domains also showed no impairment in cell surface expression at steady state. A truncated receptor containing only the large amino-terminal extracellular ligand binding domain (ECD) is secreted into the culture medium and Sar1H79G inhibits this secretion. ECD receptor variants with the cysteines essential for intermolecular disulfide-linked dimerization mutated to serine or four of the asparagine sites for N-glycosylation mutated to alanine also disrupt secretion, indicting proper ECD conformation is critical for forward transport of this receptor.
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