Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, the Institute for Advanced Studies, Wuhan University, Wuhan 430072, China.
Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, the Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
J Lipid Res. 2018 Mar;59(3):507-514. doi: 10.1194/jlr.M082149. Epub 2018 Jan 20.
The transport of LDL-derived cholesterol from lysosomes to peroxisomes is facilitated by membrane contacts formed between the lysosomal protein synaptotagmin VII and the peroxisomal lipid phosphatidylinositol 4, 5-bisphosphate [PI(4,5)P]. Here, we used RNA interference to search for regulators of PI(4,5)P and to study the effects of altered PI(4,5)P homeostasis on cholesterol transport. We found that knockdown of phosphatidylinositol 5-phosphate 4-kinase type-2 α (PIP4K2A) reduced peroxisomal PI(4,5)P levels, decreased lysosome-peroxisome membrane contacts, and increased accumulation of lysosomal cholesterol in human SV-589 fibroblasts. Forced expression of peroxisome-localized, kinase-active PIP4K2A in the knockdown cells reduced cholesterol accumulation, and in vitro addition of recombinant PIP4K2A restored membrane contacts. These results suggest that PIP4K2A plays a critical role in intracellular cholesterol transport by upregulating PI(4,5)P levels in the peroxisomal membrane. Further research into PIP4K2A activity may inform future therapeutic interventions for managing lysosomal storage disorders.
LDL 衍生胆固醇从溶酶体向过氧化物酶体的转运是由溶酶体蛋白突触结合蛋白 VII 与过氧化物体脂磷脂酰肌醇 4,5-二磷酸 [PI(4,5)P] 之间形成的膜接触促进的。在这里，我们使用 RNA 干扰来寻找 PI(4,5)P 的调节剂，并研究改变 PI(4,5)P 动态平衡对胆固醇转运的影响。我们发现，磷酸肌醇 5-磷酸 4-激酶 2A（PIP4K2A）的敲低降低了过氧化物体的 PI(4,5)P 水平，减少了溶酶体-过氧化物体膜接触，并增加了人 SV-589 成纤维细胞中溶酶体胆固醇的积累。在敲低细胞中过表达定位于过氧化物体的激酶活性 PIP4K2A 减少了胆固醇的积累，并且体外添加重组 PIP4K2A 恢复了膜接触。这些结果表明，PIP4K2A 通过上调过氧化物体膜中的 PI(4,5)P 水平在细胞内胆固醇转运中发挥关键作用。进一步研究 PIP4K2A 的活性可能为管理溶酶体贮积症的未来治疗干预提供信息。
