Multimerization of Glycosylphosphatidylinositol-anchored High Density Lipoprotein-binding Protein 1 (GPIHBP1) and Familial Chylomicronemia from a Serine-to-Cysteine Substitution in GPIHBP1 Ly6 Domain
Multimerization of Glycosylphosphatidylinositol-anchored High Density Lipoprotein-binding Protein 1 (GPIHBP1) and Familial Chylomicronemia from a Serine-to-Cysteine Substitution in GPIHBP1 Ly6 Domain
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DOI：
10.1074/jbc.m114.558528
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发表时间：
2014-07-11
影响因子：
4.8
通讯作者：
Beigneux, Anne P.
中科院分区：
文献类型：
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作者：
Plengpanich, Wanee;Young, Stephen G.;Beigneux, Anne P.
GPIHBP 1是微血管内皮细胞的糖基磷脂酰肌醇锚定的糖蛋白，在间质空间内结合脂蛋白脂肪酶（LPL）并将其穿过内皮细胞转运至毛细血管腔。GPIHBP 1结合LPL的能力取决于Ly 6结构域，Ly 6结构域是一个含有10个半胱氨酸的三指结构和二硫键形成的保守模式。在这里，我们报告了一个严重的高脂血症患者谁是纯合子的GPIHBP 1点突变，转换成丝氨酸在GPIHBP 1的Ly 6域（Ser-107）的半胱氨酸。两个高胆红素血症的兄弟姐妹是相同突变的纯合子。所有三个纯合子在肝素前血浆中LPL水平非常低。我们怀疑GPIHBP 1-S107 C中额外的半胱氨酸可能会阻止蛋白质运输到细胞表面，但事实并非如此。然而，细胞表面上几乎所有的GPIHBP 1-S107 C都是二硫键连接的二聚体和多聚体的形式，而野生型GPIHBP 1主要是单体。昆虫细胞GPIHBP 1表达系统证实了GPIHBP 1-S107 C形成二硫键连接的二聚体和形成多聚体的倾向。功能研究表明，只有GPIHBP 1单体结合LPL。与该发现一致，在基于细胞的或无细胞的结合测定中，LPL与GPIHBP 1-S107 C没有结合。我们的结论是，在GPIHBP 1的Ly 6基序中的一个额外的半胱氨酸导致GPIHBP 1的多聚化，LPL结合缺陷，和严重的高脂血症。
GPIHBP1, a glycosylphosphatidylinositol-anchored glycoprotein of microvascular endothelial cells, binds lipoprotein lipase (LPL) within the interstitial spaces and transports it across endothelial cells to the capillary lumen. The ability of GPIHBP1 to bind LPL depends on the Ly6 domain, a three-fingered structure containing 10 cysteines and a conserved pattern of disulfide bond formation. Here, we report a patient with severe hypertriglyceridemia who was homozygous for a GPIHBP1 point mutation that converted a serine in the GPIHBP1 Ly6 domain (Ser-107) to a cysteine. Two hypertriglyceridemic siblings were homozygous for the same mutation. All three homozygotes had very low levels of LPL in the preheparin plasma. We suspected that the extra cysteine in GPIHBP1-S107C might prevent the trafficking of the protein to the cell surface, but this was not the case. However, nearly all of the GPIHBP1-S107C on the cell surface was in the form of disulfide-linked dimers and multimers, whereas wild-type GPIHBP1 was predominantly monomeric. An insect cell GPIHBP1 expression system confirmed the propensity of GPIHBP1-S107C to form disulfide-linked dimers and to form multimers. Functional studies showed that only GPIHBP1 monomers bind LPL. In keeping with that finding, there was no binding of LPL to GPIHBP1-S107C in either cell-based or cell-free binding assays. We conclude that an extra cysteine in the GPIHBP1 Ly6 motif results in multimerization of GPIHBP1, defective LPL binding, and severe hypertriglyceridemia.