LXR Agonism Upregulates the Macrophage ABCA1/Syntrophin Protein Complex That Can Bind ApoA-I and Stabilized ABCA1 Protein, but Complex Loss Does Not Inhibit Lipid Efflux.
LXR Agonism Upregulates the Macrophage ABCA1/Syntrophin Protein Complex That Can Bind ApoA-I and Stabilized ABCA1 Protein, but Complex Loss Does Not Inhibit Lipid Efflux.
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DOI：
10.1021/acs.biochem.5b00894
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发表时间：
2015-11-24
期刊：
影响因子：
2.9
通讯作者：
Fitzgerald ML
中科院分区：
文献类型：
--
作者：
Tamehiro N;Park MH;Hawxhurst V;Nagpal K;Adams ME;Zannis VI;Golenbock DT;Fitzgerald ML
巨噬细胞ABCA1排出脂质，具有抗炎活性。合成营养素是胞质PDZ蛋白的支架因子，可以与ABCA1结合并调节其活性。然而，许多或“许多”评估ABCA1-合并素相互作用的功能的数据是基于非巨噬细胞中的过度表达。为了评估巨噬细胞的内源性复合体功能，我们从ABCA1+/+和ABCA1−/−小鼠中分离出永生化的巨噬细胞，并展示了它们的表型概括了原代巨噬细胞。ABCA1+/+细胞表达CD11b和F4/80巨噬细胞标志物，并显著上调LXR核激素激动剂对胆固醇的外流。相比之下，永生化的ABCA1−/−巨噬细胞对apoA-I没有外流。作为对内毒素的反应，ABCA1CD14巨噬细胞表现出促炎变化，包括细胞表面−/−表达水平增加，IL-6和IL-12mRNA水平增加11-26倍。根据表型的概括，我们用这些株系证明了ABCA1-合成素蛋白复合体被LXR激动剂上调，并能与apoA-I结合。此外，在永生化巨噬细胞中，α1/β2合体营养素丢失调节了ABCA1细胞表面的水平并诱导了促炎基因的表达。然而，已知的与ABCA1结合的所有三种合体营养素亚型的丢失并不损害永生化或原代巨噬细胞的脂质外流。因此，ABCA1-Syntroin蛋白复合体不是ABCA1巨噬细胞脂质外流所必需的，但确实与apoA-I直接相互作用，并可以调节由apoA-I稳定的细胞表面ABCA1池。
Macrophage ABCA1 effluxes lipid and has anti-inflammatory activity. The syntrophins, which are cytoplasmic PDZ protein scaffolding factors, can bind ABCA1 and modulate its activity. However, many or “much” of the data assessing the function of the ABCA1–syntrophin interaction are based on overexpression in nonmacrophage cells. To assess endogenous complex function in macrophages, we derived immortalized macrophages from Abca1+/+ and Abca1−/− mice and show their phenotype recapitulates primary macrophages. Abca1+/+ lines express the CD11B and F4/80 macrophage markers and markedly upregulate cholesterol efflux in response to LXR nuclear hormone agonists. In contrast, immortalized Abca1−/− macrophages show no efflux to apoA-I. In response to LPS, Abca1−/− macrophages display pro-inflammatory changes, including an increased level of expression of cell surface CD14, and 11–26-fold higher levels of IL-6 and IL-12 mRNA. Given recapitulation of phenotype, we show with these lines that the ABCA1–syntrophin protein complex is upregulated by LXR agonists and can bind apoA-I. Moreover, in immortalized macrophages, combined α1/β2-syntrophin loss modulated ABCA1 cell surface levels and induced pro-inflammatory gene expression. However, loss of all three syntrophin isoforms known to bind ABCA1 did not impair lipid efflux in immortalized or primary macrophages. Thus, the ABCA1–syntrophin protein complex is not essential for ABCA1 macrophage lipid efflux but does directly interact with apoA-I and can modulate the pool of cell surface ABCA1 stabilized by apoA-I.