COPI–TRAPPII activates Rab18 and regulates its lipid droplet association |
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Authors: | Chunman Li Xiaomin Luo Shan Zhao Gavin KY Siu Yongheng Liang Hsiao Chang Chan Ayano Satoh Sidney SB Yu |
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Affiliation: | 1. Department of Anatomy, Histology and Developmental Biology, School of Basic Medical Sciences, Health Science Centre, Shenzhen University, Shenzhen, China;2. School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China;3. Key Laboratory of Agricultural Environmental Microbiology of MOA, College of Life Sciences, Nanjing Agricultural University, Nanjing, China;4. Epithelial Cell Biology Research Centre, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China;5. The Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan |
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Abstract: | The transport protein particle (TRAPP) was initially identified as a vesicle tethering factor in yeast and as a guanine nucleotide exchange factor (GEF) for Ypt1/Rab1. In mammals, structures and functions of various TRAPP complexes are beginning to be understood. We found that mammalian TRAPPII was a GEF for both Rab18 and Rab1. Inactivation of TRAPPII‐specific subunits by various methods including siRNA depletion and CRISPR–Cas9‐mediated deletion reduced lipolysis and resulted in aberrantly large lipid droplets. Recruitment of Rab18 onto lipid droplet (LD) surface was defective in TRAPPII‐deleted cells, but the localization of Rab1 on Golgi was not affected. COPI regulates LD homeostasis. We found that the previously documented interaction between TRAPPII and COPI was also required for the recruitment of Rab18 to the LD. We hypothesize that the interaction between COPI and TRAPPII helps bring TRAPPII onto LD surface, and TRAPPII, in turn, activates Rab18 and recruits it on the LD surface to facilitate its functions in LD homeostasis. |
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Keywords: |
COPI
lipid droplets Rab18 TRAPPC10 TRAPPC9
TRAPPII
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