Mutation G805R in the transmembrane domain of the LDL receptor gene causes familial hypercholesterolemia by inducing ectodomain cleavage of the LDL receptor in the endoplasmic reticulum.
Mutation G805R in the transmembrane domain of the LDL receptor gene causes familial hypercholesterolemia by inducing ectodomain cleavage of the LDL receptor in the endoplasmic reticulum.
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DOI：
10.1016/j.fob.2014.03.007
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发表时间：
2014
期刊：
影响因子：
2.6
通讯作者：
Leren, Trond P.
中科院分区：
文献类型：
--
作者：
Strom, Thea Bismo;Tveten, Kristian;Laerdahl, Jon K.;Leren, Trond P.
关键词：
突变 G805R 位于 LDLR 的跨膜结构域中。跨膜结构域中的极性残基诱导金属蛋白酶裂解。突变 G805R 导致前体 LDLR 数量减少。前体 LDLR 量的减少导致成熟 LDLR 量的减少。突变 G805R 阻止了跨膜域内的 γ-分泌酶裂解。低密度脂蛋白受体 (LDLR) 基因中超过 1700 个突变已被发现可导致家族性高胆固醇血症 (FH)。根据它们对 LDLR 结构和功能的影响，它们通常分为五类。然而，人们对 LDLR 基因跨膜结构域突变导致 FH 的机制知之甚少。我们研究了跨膜突变 G805R 如何影响 LDLR 的功能。根据转染 HepG2 细胞的蛋白质印迹分析，突变 G805R 减少了内质网中 120 kDa 前体 LDLR 的量。这导致细胞表面成熟的 160 kDa LDLR 数量减少。然而，在培养基中观察到大量分泌的 140 kDa G805R-LDLR 胞外域片段。用金属蛋白酶抑制剂巴马司他处理细胞很大程度上恢复了细胞裂解物中 120 和 160 kDa 形式的量，并阻止了 140 kDa 胞外域片段的分泌。总之，这些数据表明金属蛋白酶裂解内质网中 120 kDa 前体 G805R-LDLR 的胞外域。正是极性 Arg805 的存在而不是 Gly805 的缺乏导致了胞外域裂解。 Arg805 还阻止跨膜域内的 γ-分泌酶裂解。可以想象，在疏水膜脂质双层内引入带电残基，会导致 120 kDa G805R-LDLR 在内质网膜中的掺入效率较低，并使其成为金属蛋白酶裂解的底物。
Mutation G805R is in the transmembrane domain of the LDLR. A polar residue in the transmembrane domain induced metalloproteinase cleavage. Mutation G805R caused reduced amounts of the precursor LDLR. Reduced amounts of precursor LDLR led to reduced amounts of the mature LDLR. Mutation G805R prevented γ-secretase cleavage within the transmembrane domain. More than 1700 mutations in the low density lipoprotein receptor (LDLR) gene have been found to cause familial hypercholesterolemia (FH). These are commonly divided into five classes based upon their effects on the structure and function of the LDLR. However, little is known about the mechanism by which mutations in the transmembrane domain of the LDLR gene cause FH. We have studied how the transmembrane mutation G805R affects the function of the LDLR. Based upon Western blot analyses of transfected HepG2 cells, mutation G805R reduced the amounts of the 120 kDa precursor LDLR in the endoplasmic reticulum. This led to reduced amounts of the mature 160 kDa LDLR at the cell surface. However, significant amounts of a secreted 140 kDa G805R-LDLR ectodomain fragment was observed in the culture media. Treatment of the cells with the metalloproteinase inhibitor batimastat largely restored the amounts of the 120 and 160 kDa forms in cell lysates, and prevented secretion of the 140 kDa ectodomain fragment. Together, these data indicate that a metalloproteinase cleaved the ectodomain of the 120 kDa precursor G805R-LDLR in the endoplasmic reticulum. It was the presence of the polar Arg805 and not the lack of Gly805 which led to ectodomain cleavage. Arg805 also prevented γ-secretase cleavage within the transmembrane domain. It is conceivable that introducing a charged residue within the hydrophobic membrane lipid bilayer, results in less efficient incorporation of the 120 kDa G805R-LDLR in the endoplasmic reticulum membrane and makes it a substrate for metalloproteinase cleavage.
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影响因子：
64.5
作者：
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通讯作者：
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影响因子：
15
作者：
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通讯作者：
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影响因子：
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影响因子：
5.4
作者：
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通讯作者：
Kulseth, Mari A.