Cathepsin D, a lysosomal protease, regulates ABCA1-mediated lipid efflux
Cathepsin D, a lysosomal protease, regulates ABCA1-mediated lipid efflux
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DOI：
10.1074/jbc.m605095200
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发表时间：
2006-12-29
影响因子：
4.8
通讯作者：
Marcel, Yves L.
中科院分区：
文献类型：
--
作者：
Haidar, Bassam;Kiss, Robert S.;Marcel, Yves L.
为了确定参与血浆高密度脂蛋白（HDL）胆固醇（HDL- c）水平调节的基因，对低HDL- c患者和年龄和性别匹配的对照组（正常HDL- c）进行了广泛的表征。对来自低HDL受试者的胆固醇负荷单核细胞来源的巨噬细胞进行了比较转录组分析，这些巨噬细胞被分成有或没有胆固醇外排缺陷或ABCA1突变的组。与对照组相比，低HDL组明显存在差异调节基因簇。特别值得注意的是，在低HDL-C受试者的单核细胞源性巨噬细胞中，组织蛋白酶D (CTSD)（一种溶酶体蛋白酶）的表达减少了50%，尤其是那些胆固醇外排缺陷但ABCA1没有突变的人（p < 0.01）。这些结果通过逆转录- pcr得到验证，并在第二个队列中得到重复。我们在这里表明，分别通过胃抑素或CTSD小干扰RNA阻断CTSD的活性或表达，可使巨噬细胞和CHO细胞中ABCA1的表达和蛋白丰度以及载脂蛋白a - i介导的脂质外排减少70%以上。相反，CTSD的表达增加了ABCA1 mRNA的表达和细胞ABCA1蛋白的表达。与其在蛋白酶水解过程中的作用一致，CTSD功能失活导致鞘糖脂和游离胆固醇在晚期内体/溶酶体中积累，这种表型类似于NPC1缺陷。抑制CTSD还会导致ABCA1在溶酶体腔室中的滞留，减少其向质膜的运输。这些研究表明，CTSD在细胞内胆固醇运输和abca1介导的外排中具有新的和潜在的重要作用。因此，CTSD表达降低可能导致血浆HDL-C水平降低。
To identify genes involved in the regulation of plasma high density lipoprotein (HDL) cholesterol (HDL-C) levels, patients with low HDL-C and age- and sex-matched controls (normal HDL-C) were extensively characterized. Comparative transcriptome analysis was carried out in cholesterol-loaded monocyte-derived macrophages from low HDL subjects segregated into groups with or without cholesterol efflux defects or ABCA1 mutations. Clusters of differentially regulated genes were evident in the low HDL groups as compared with controls. Of particular note, expression of cathepsin D (CTSD), a lysosomal proteinase, was reduced by similar to 50% in monocyte-derived macrophages of low HDL-C subjects, most significantly those with cholesterol efflux defects but without mutations in ABCA1 (p < 0.01). These results were verified by reverse transcription-PCR and replicated in a second cohort. We show here that blocking the activity or expression of CTSD, by pepstatin or CTSD small interfering RNA, respectively, reduced ABCA1 expression and protein abundance in both macrophages and CHO cells and apolipoprotein A-I-mediated lipid efflux by more than 70%. Conversely, expression of CTSD increased both ABCA1 mRNA expression and cellular ABCA1 protein. Consistent with its role in the proteolytic processing of prosaposin, inactivation of CTSD function resulted in the accumulation of glycosphingolipid and free cholesterol in late endosomes/lysosomes, a phenotype similar to NPC1 deficiency. Inhibition of CTSD also caused retention of ABCA1 in lysosomal compartments, reducing its trafficking to the plasma membrane. These studies demonstrate a novel and potentially important role for CTSD in intracellular cholesterol trafficking and ABCA1-mediated efflux. Therefore, decreased CTSD expression may contribute to low plasma HDL-C levels.