Low Density Lipoprotein Receptor Variants in the Beta-Propeller Subdomain and Their Functional Impact
Low Density Lipoprotein Receptor Variants in the Beta-Propeller Subdomain and Their Functional Impact
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DOI：
10.3389/fgene.2020.00691
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发表时间：
2020-06-30
影响因子：
3.7
通讯作者：
Fajkusova, Lenka
中科院分区：
文献类型：
--
作者：
Duskova, Lucie;Nohelova, Lucie;Fajkusova, Lenka
背景：低密度脂蛋白受体基因的致病性变异与家族性高胆固醇血症有关。这些变体中的一些可能导致LDLR蛋白的不正确折叠，然后在细胞内积累，并且不能实现其内化LDL颗粒的功能。我们分析了定位于表皮生长因子前体同源结构域β-螺旋桨的10种LDLR变体的功能影响。方法：以转染人LDLR基因的中国仓鼠卵巢细胞为研究对象，采用活细胞成像显微镜、流式细胞仪和qRT-PCR技术，对LDLR蛋白变异体进行结构分析。(1)埋在3D蛋白质结构内的变体表达在内质网（ER）中积累的蛋白质，没有或减少质膜定位和LDL颗粒内化，并且与ER驻留伴侣的基因表达增加相关。(2)这些变异体定位于3D蛋白结构的表面，LDLR质膜定位和LDL颗粒内化略有减少，并且与ER驻留分子伴侣的mRNA水平没有增加相关。(3)这些变异体定位于蛋白质三维结构的表面，但表达的蛋白质具有与第1组相似的细胞反应。结论：所有分析的LDLR变异体均被评估为致病性的，但对蛋白质定位和功能以及ER应激相关基因表达的影响不同。
Background: Pathogenic variants in the low density lipoprotein receptor gene are associated with familial hypercholesterolemia. Some of these variants can result in incorrect folding of the LDLR protein, which is then accumulated inside the cell and cannot fulfill its function to internalize LDL particles. We analyzed the functional impact of 10 LDLR variants localized in the beta-propeller of epidermal growth factor precursor homology domain. The experimental part of the work was complemented by a structural analysis on the basis of 3D LDLR protein structure.Methods: T-Rex Chinese hamster ovary cells transfected with the human LDLR gene were used for live cell imaging microscopy, flow cytometry, and qRT-PCR analysis.Results: Our results showed that the analyzed LDLR protein variants can be divided into three groups. (1) The variants buried inside the 3D protein structure expressing proteins accumulated in the endoplasmic reticulum (ER) with no or reduced plasma membrane localization and LDL particle internalization, and associated with an increased gene expression of ER-resident chaperones. (2) The variants localized on the surface of 3D protein structure with slightly reduced LDLR plasma membrane localization and LDL particle internalization, and associated with no increased mRNA level of ER-resident chaperones. (3) The variants localized on the surface of the 3D protein structure but expressing proteins with cell responses similar to the group 1.Conclusion: All analyzed LDLR variants have been evaluated as pathogenic but with different effects on protein localization and function, and expression of genes associated with ER stress.