Stable reduction of STARD4 alters cholesterol regulation and lipid homeostasis
Stable reduction of STARD4 alters cholesterol regulation and lipid homeostasis
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DOI：
10.1016/j.bbalip.2020.158609
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发表时间：
2020-04-01
影响因子：
4.8
通讯作者：
Maxfield, Frederick R.
中科院分区：
文献类型：
--
作者：
Iaea, David B.;Spahr, Zachary R.;Maxfield, Frederick R.
STARD 4是进化上保守的START基因家族的成员，是一种可溶性固醇转运蛋白，参与胆固醇传感和维持细胞内稳态。STARD 4广泛表达，并已显示在脂质体以及细胞器之间转移固醇。然而，STARD 4基因敲除小鼠缺乏明显的表型，因此STARD 4的整体作用尚不清楚。为了模拟细胞中STARD 4的长期消耗，我们使用短发夹RNA技术来稳定地降低人U2 OS骨肉瘤细胞（STARD 4-KD）中的STARD 4表达。我们发现，STARD 4-KD细胞显示增加的总胆固醇，细胞膜和内吞再循环室之间的胆固醇运输较慢，和增加的质膜流动性。这些作用都可以通过短发夹RNA抗性STARD 4构建体的瞬时表达来挽救。一些胆固醇增加是由于晚期内体或溶酶体中的过量储存。为了理解减少的STARD 4的作用，我们进行了对照和STARD 4-KD细胞的转录和脂质组学分析。STARD 4的减少激活了改变膜组成和脂质稳态的代偿机制。基于这些观察结果，我们提出STARD 4作为一个关键的甾醇转运蛋白参与甾醇传感和维持脂质稳态。
STARD4, a member of the evolutionarily conserved START gene family, is a soluble sterol transport protein implicated in cholesterol sensing and maintenance of cellular homeostasis. STARD4 is widely expressed and has been shown to transfer sterol between liposomes as well as organelles in cells. However, STARD4 knockout mice lack an obvious phenotype, so the overall role of STARD4 is unclear. To model long term depletion of STARD4 in cells, we use short hairpin RNA technology to stably decrease STARD4 expression in human U2OS osteosarcoma cells (STARD4-KD). We show that STARD4-KD cells display increased total cholesterol, slower cholesterol trafficking between the plasma membrane and the endocytic recycling compartment, and increased plasma membrane fluidity. These effects can all be rescued by transient expression of a short hairpin RNA-resistant STARD4 construct. Some of the cholesterol increase was due to excess storage in late endosomes or lysosomes. To understand the effects of reduced STARD4, we carried out transcriptional and lipidomic profiling of control and STARD4-KD cells. Reduction of STARD4 activates compensatory mechanisms that alter membrane composition and lipid homeostasis. Based on these observations, we propose that STARD4 functions as a critical sterol transport protein involved in sterol sensing and maintaining lipid homeostasis.