Ubiquitination Is Associated with Lysosomal Degradation of Cell Surface-Resident ATP-Binding Cassette Transporter A1 (ABCA1) Through the Endosomal Sorting Complex Required for Transport (ESCRT) Pathway
Ubiquitination Is Associated with Lysosomal Degradation of Cell Surface-Resident ATP-Binding Cassette Transporter A1 (ABCA1) Through the Endosomal Sorting Complex Required for Transport (ESCRT) Pathway
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DOI：
10.1002/hep.24387
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发表时间：
2011-08-01
期刊：
影响因子：
13.5
通讯作者：
Sugiyama, Yuichi
中科院分区：
文献类型：
--
作者：
Mizuno, Tadahaya;Hayashi, Hisamitsu;Sugiyama, Yuichi
ATP结合盒转运体A1（ABCA 1）在肝脏高密度脂蛋白的生物合成中起重要作用，并通过介导细胞内胆固醇和磷脂向载脂蛋白A-I（apoA-I）的外排来防止巨噬细胞内泡沫细胞的形成。我们目前的研究探讨了细胞表面驻留ABCA 1的降解机制，重点是泛素化。免疫共沉淀研究表明，泛素化ABCA 1存在于人肝癌细胞系HuH-7、小鼠肝脏细胞和从人急性单核细胞白血病细胞系THP-1分化的巨噬细胞（THP-1巨噬细胞）的质膜中。在HuH-7细胞中，细胞表面驻留的ABCA 1的降解被泛素的显性负性形式的过表达抑制。此外，通过敲低肝细胞生长因子调节的酪氨酸激酶底物（HRS），破坏转运所需的内体分选复合物（ESCRT）途径，这是遍在化介导的溶酶体降解的主要机制，显着延迟了细胞表面的降解驻留ABCA 1。这伴随着ABCA 1表达以及apoA-I介导的[（3）H]-胆固醇流出功能的增加。在钙蛋白酶抑制剂处理后也观察到HRS敲低的作用，据报道这延缓了ABCA 1降解。在THP-1巨噬细胞中证实了通过HRS敲低诱导ABCA 1。结论：结合溶酶体抑制剂处理增加HuH-7和THP-1巨噬细胞中ABCA 1表达的事实，这些结果表明泛素化通过ESCRT途径介导细胞表面驻留ABCA 1的溶酶体降解，从而控制ABCA 1的表达和胆固醇流出功能。这种机制似乎独立于钙蛋白酶参与的途径介导ABCA 1降解。因此，ABCA 1泛素化的调节可能成为抗动脉粥样硬化药物的潜在新治疗靶点。（肝脏学2011;54：631-643）
ATP-binding cassette transporter A1 (ABCA1) plays an essential role in the biogenesis of high-density lipoprotein in liver and in the prevention of foam cell formation in macrophages by mediating the efflux of cellular cholesterol and phospholipids to apolipoprotein A-I (apoA-I). Our current study investigated the mechanism of degradation of cell surface-resident ABCA1, focusing on ubiquitination. A coimmunoprecipitation study indicated the presence of ubiquitinated ABCA1 in the plasma membrane of the human hepatoma cell line, HuH-7, of cells from mouse liver, and of macrophages differentiated from the human acute monocytic leukemia cell line, THP-1 (THP-1 macrophages). In HuH-7 cells, degradation of cell surface-resident ABCA1 was inhibited by the overexpression of a dominant-negative form of ubiquitin. Moreover, the disruption of the endosomal sorting complex required for transport (ESCRT) pathway, a dominant mechanism for ubiquitination-mediated lysosomal degradation, by the knockdown of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), significantly delayed the degradation of cell surface-resident ABCA1. This was accompanied by an increase in ABCA1 expression as well as in apoA-I-mediated [(3)H]-cholesterol efflux function. The effect of HRS knockdown was also observed after calpain inhibitor treatment, which is reported to retard ABCA1 degradation. The induction of ABCA1 by HRS knockdown was confirmed in THP-1 macrophages. Conclusion: Together with the fact that lysosomal inhibitor treatments increased ABCA1 expression in HuH-7 and THP-1 macrophages, these results suggest that ubiquitination mediates the lysosomal degradation of cell surface-resident ABCA1 through the ESCRT pathway, and thereby controls the expression and cholesterol efflux function of ABCA1. This mechanism seems to mediate ABCA1 degradation independently of the calpain-involving pathway. The modulation of ABCA1 ubiquitination could thus be a potential new therapeutic target for antiatherogenic drugs. (HEPATOLOGY 2011;54:631-643)