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Structural insights into human TM6SF2-mediated cholesterol coordination in apoB-100 interactions

This article is a preprint and has not been certified by peer review.

Authors

    Xiaoxiao Jia,  
    Xiaoxiao Jia
    • MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Interdisciplinary Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
    Qiaoyue Chen,  
    Qiaoyue Chen
    • MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Interdisciplinary Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
    Zhihua Wang,  
    Zhihua Wang
    • Anhui Provincial Laboratory of Inflammatory and Immunity Disease, Anhui Institute of Innovative Drugs, School of Pharmaceutical Sciences, Anhui Medical University, Hefei, 230032, China
    Linlin Zheng,  
    Linlin Zheng
    • MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Interdisciplinary Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
    Chunping Sun,  
    Chunping Sun
    • Department of Endocrinology, The Third Affiliated Hospital of Anhui Medical University (The First People’s Hospital of Hefei), Anhui Medical University, Hefei 230001, China
    Suowen Xu,  
    Suowen Xu
    • Department of Endocrinology and Metabolism, the First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, 230026, Hefei, China
    Mengchan Liu,  
    Mengchan Liu
    • MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Interdisciplinary Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
    Hongwu Qian
    Hongwu Qian
    • 中国科学技术大学生命科学与医学部
Categories
Biochemistry & Biophysics
Keywords
MASLD; TM6SF2; EXPERA; VLDL lipidation; apoB-100

Abstract

Transmembrane 6 superfamily member 2 (TM6SF2) is a liver- and intestine-enriched ER membrane protein that promotes VLDL lipidation/secretion and protects against hepatic lipid accumulation. The common E167K mutation of TM6SF2 impairs protein stability and VLDL secretion while showing a paradoxical protective lipid/cardiovascular profile. However, it remains elusive how TM6SF2 contributes to lipoprotein maturation. Here, we first determined the cryo-EM structure of human TM6SF2 using HEK293F-expressed proteins. TM6SF2 forms a dimer, with each protomer comprising 10 transmembrane helices (TMs) that can be divided into an N-terminal domain (NTD, TM1-2) and two EXPERA domains—EXPERA-N (TM3-6) and EXPERA-C (TM7-10). Further analysis revealed that an endogenous cholesterol molecule was coordinated by the NTD and EXPEART-N domains. Disruption of cholesterol coordination compromised the TM6SF2-apoB-100 interaction in pull-down assays. When the structure was determined using proteins expressed under cholesterol-depleted conditions, the cholesterol densities disappeared, accompanied by more flexible conformations of the NTD and EXPEART-N domains. Molecular dynamics simulations suggested that the luminal loop between TM5 and TM6 of the EXPEART-N domain (TM5-6 linker) becomes more flexible under cholesterol-free conditions. The TM5-6 linker is essential for apoB-100 interaction, as supported by the AlphaFold3-predicted structure and pull-down assays. The common E167K mutation is located on the TM5-6 linker and weakens its direct interaction with apoB-100. Together, these observations suggest that cholesterol contributes to the TM6SF2-apoB-100 interaction by maintaining a stable conformation of the TM5-6 linker.

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https://doi.org/10.65215/LTSpreprints.2026.10.15.000363

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2026-10-16

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Jia, X., Chen, Q., Wang, Z., Zheng, L., Sun, C., Xu, S., Liu, M., & Qian, H. (2026). Structural insights into human TM6SF2-mediated cholesterol coordination in apoB-100 interactions. LangTaoSha Preprint Server. https://doi.org/10.65215/LTSpreprints.2026.10.15.000363

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