Cholesterol transport through the peroxisome-ER membrane contacts tethered by PI(4,5)P2 and extended synaptotagmins
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Most mammalian cells take up cholesterol from low-density lipoproteins (LDLs) via receptor-mediated endocytosis. After reaching lysosomes, LDL-derived cholesterol continues to transport to downstream organelles including the ER for specific structural and functional needs. Peroxisomes are recently found to receive cholesterol from lysosomes through lysosome-peroxisome membrane contacts. However, whether and how cholesterol is conveyed from peroxisomes to the ER remain unknown. Here, by combining high-resolution microscopic analyses and in vitro reconstitution of highly purified organelles or artificial liposomes, we demonstrate that peroxisomes form membrane contacts with the ER through the interaction between peroxisomal PI(4,5)P2 and ER-resident extended synaptotagmin-1, 2 and 3 (E-Syts). Depletion of peroxisomal PI(4,5)P2 or E-Syts markedly decreases peroxisome-ER membrane contacts and induces cholesterol accumulation in lysosomes. Furthermore, we show that cholesterol is delivered from 3H-labeled peroxisomes or PI(4,5)P2-containing liposomes to the ER in vitro, and that the presence of peroxisomes augments cholesterol transfer from lysosomes to the ER. Together, our study reveals a new cholesterol transport pathway along the lysosome-peroxisome-ER membrane contacts in the cell.
We thank Dr. Wei Qi for helpful discussion and critical reading of the manuscript. We thank the center for Biological Imaging, Institute of Biophysics, Chinese Academy of Science for 3D TEM experiments, and Xin-Tong Niu and Yun Feng for their help with 3D TEM images. We thank Dr. Ming-Liang Tang for his help with SR-SIM images. This work was supported by the National Natural Science Foundation of China (91754102, 31771568, 31690102, 31600651 and 31701030), National Key Research and Development Project of the Ministry of Science and Technology of China (2016YFA0500100), Shenzhen City Technology Basic Research Program (JCYJ20170818144026198), Science and Technology Department of Hubei Province (2017CFB617) and the 111 Project of Ministry of Education of China (B16036).
Compliance and ethics The authors declare that they have no conflict of interests.
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