SPTLC1 binds ABCA1 to negatively regulate trafficking and cholesterol efflux activity of the transporter.
SPTLC1 binds ABCA1 to negatively regulate trafficking and cholesterol efflux activity of the transporter.
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SPTLC1 与 ABCA1 结合，负向调节转运蛋白的运输和胆固醇流出活性。
DOI：
10.1021/bi800182t
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发表时间：
2008
期刊：
影响因子：
2.9
通讯作者：
Fitzgerald,MichaelL
中科院分区：
文献类型：
--
作者：
Tamehiro,Norimasa;Zhou,Suiping;Okuhira,Keiichiro;Benita,Yair;Brown,CariE;Zhuang,DebbieZ;Latz,Eicke;Hornemann,Thorsten;vonEckardstein,Arnold;Xavier,RamnikJ;Freeman,MasonW;Fitzgerald,MichaelL
ABCA 1将胆固醇和磷脂转运至新生HDL颗粒在脂蛋白代谢和巨噬细胞胆固醇稳态中起着重要作用。ABCA 1活性在转录水平和翻译后水平都受到调节。为了探索转运蛋白的翻译后调节机制，我们使用亲和纯化和质谱法来鉴定结合ABCA 1并影响其活性的蛋白质。以前，我们证明了β1-syntrophin刺激ABCA 1活性之间的相互作用，至少部分减缓了转运蛋白的降解。这项工作表明，丝氨酸棕榈酰转移酶的一个亚基，SPTLC 1，但不是亚基2（SPTLC 2），与ABCA 1共纯化，并负调控其功能。在人类THP-I巨噬细胞和小鼠肝脏中，通过免疫共沉淀检测到ABCA 1 − SPTLC 1复合物，表明相互作用发生在ABCA 1活性对HDL生成至关重要的细胞环境中。用多球壳菌素对SPTLC 1的药理学抑制导致SPTLC 1 − ABCA 1复合物的破坏，以及SPTLC 1表达的siRNA敲低都刺激ABCA 1流出近60%（p< 0.05）。相反，SPTLC 1的显性阴性突变体抑制ABCA 1外排，表明鞘磷脂合成水平降低不能解释多球壳菌素对ABCA 1活性的影响。在293细胞中，SPTLC 1对ABCA 1活性的抑制导致ABCA 1从内质网退出的阻断。相比之下，巨噬细胞的多球菌素处理增加了细胞表面ABCA 1的水平。在复合物中，这些结果表明ABCA 1和SPTLC 1的物理相互作用导致ABCA 1活性降低，并且这种相互作用的抑制产生增强的胆固醇流出。
ABCA1 transport of cholesterol and phospholipids to nascent HDL particles plays a central role in lipoprotein metabolism and macrophage cholesterol homeostasis. ABCA1 activity is regulated both at the transcriptional level and at the post-translational level. To explore mechanisms involved in the post-translational regulation of the transporter, we have used affinity purification and mass spectrometry to identify proteins that bind ABCA1 and influence its activity. Previously, we demonstrated that an interaction between β1-syntrophin stimulated ABCA1 activity, at least in part, be slowing the degradation of the transporter. This work demonstrates that one subunit of the serine palmitoyltransferase enzyme, SPTLC1, but not subunit 2 (SPTLC2), is copurified with ABCA1 and negatively regulates its function. In human THP-I macrophages and in mouse liver, the ABCA1−SPTLC1 complex was detected by co-immunoprecipitation, demonstrating that the interaction occurs in cellular settings where ABCA1 activity is critical for HDL genesis. Pharmacologic inhibition of SPTLC1 with myriocin, which resulted in the disruption of the SPTLC1−ABCA1 complex, and siRNA knockdown of SPTLC1 expression both stimulated ABCA1 efflux by nearly 60% (p< 0.05). In contrast, dominant-negative mutants of SPTLC1 inhibited ABCA1 efflux, indicating that a reduced level of sphingomyelin synthesis could not explain the effect of myriocin on ABCA1 activity. In 293 cells, the SPTLC1 inhibition of ABCA1 activity led to the blockade of the exit of ABCA1 from the endoplasmic reticulum. In contrast, myriocin treatment of macrophages increased the level of cell surface ABCA1. In composite, these results indicate that the physical interaction of ABCA1 and SPTLC1 results in reduction of ABCA1 activity and that inhibition of this interaction produces enhanced cholesterol efflux.
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DOI：
--
发表时间：
2004
期刊：
J Biol Chem 279
影响因子：
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作者：
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