Janus kinase 2 modulates the lipid-removing but not protein-stabilizing interactions of amphipathic helices with ABCA1
Janus kinase 2 modulates the lipid-removing but not protein-stabilizing interactions of amphipathic helices with ABCA1
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DOI：
10.1194/jlr.m500240-jlr200
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发表时间：
2006-01-01
影响因子：
6.5
通讯作者：
Oram, JF
中科院分区：
文献类型：
--
作者：
Tang, CR;Vaughan, AM;Oram, JF
ABCA 1介导细胞胆固醇和磷脂向HDL载脂蛋白的转运。载脂蛋白A-I（apoA-I）与ABCA 1表达细胞的相互作用引发了几种反应，包括清除细胞脂质，稳定ABCA 1蛋白和激活Janus激酶2（JAK 2）。在这里，我们使用合成的载脂蛋白模拟肽来表征这些反应之间的关系。含有一个L-或D-氨基酸的两亲性螺旋的肽（2F、D-2F或4F）和含有两个螺旋的肽（37 pA）都促进ABCA 1依赖性胆固醇流出，竞争apoA-I与ABCA 1表达细胞的结合，阻断apoA-I与ABCA 1的共价交联，并抑制ABCA 1降解。37 pA与ABCA 1交联，证实了两亲性螺旋与ABCA 1的直接结合。2F、4F、37 pA和D-37 pA均能刺激JAK 2的自磷酸化。JAK 2的抑制大大减少了肽介导的胆固醇流出，肽结合ABCA 1表达细胞，肽交联ABCA 1，表明这些过程需要一个活跃的JAK 2。相反，apoA-I和肽稳定ABCA 1蛋白，即使在没有活性JAK 2的情况下，这意味着这个过程是独立的JAK 2和脂质流出促进结合的两亲性螺旋ABCA 1。这些发现表明，两亲性螺旋通过几种不同的机制协调ABCA 1的活性，这些机制可能涉及不同的细胞表面结合位点。
ABCA1 mediates the transport of cellular cholesterol and phospholipids to HDL apolipoproteins. Apolipoprotein A-I (apoA-I) interactions with ABCA1-expressing cells elicit several responses, including removing cellular lipids, stabilizing ABCA1 protein, and activating Janus kinase 2 (JAK2). Here, we used synthetic apolipoprotein-mimetic peptides to characterize the relationship between these responses. Peptides containing one amphipathic helix of L- or D-amino acids (2F, D-2F, or 4F) and a peptide containing two helices (37pA) all promoted ABCA1-dependent cholesterol efflux, competed for apoA-I binding to ABCA1-expressing cells, blocked covalent cross-linking of apoA-I to ABCA1, and inhibited ABCA1 degradation. 37pA was crosslinked to ABCA1, confirming the direct binding of amphipathic helices to ABCA1. 2F, 4F, 37pA, and D-37pA all stimulated JAK2 autophosphorylation. Inhibition of JAK2 greatly reduced peptide-mediated cholesterol efflux, peptide binding to ABCA1-expressing cells, and peptide crosslinking to ABCA1, indicating that these processes require an active JAK2. In contrast, apoA-I and peptides stabilized ABCA1 protein even in the absence of an active JAK2, implying that this process is independent of JAK2 and lipid efflux-promoting binding of amphipathic helices to ABCA1. These findings show that amphipathic helices coordinate the activity of ABCA1 by several distinct mechanisms that are likely to involve different cell surface binding sites.