Download MendeleyStructure and function of TM6SF1 reveals role in mTORC1 signaling.
Hong, S., Jia, L., Wang, R., Elghobashi-Meinhardt, N., Hobbs, H.H., Li, X.(2026) Proc Natl Acad Sci U S A 123: e2622424123-e2622424123
- PubMed: 42735304 Search on PubMed
- DOI: https://doi.org/10.1073/pnas.2622424123
- Primary Citation Related Structures:
10UP, 11BR - PubMed Abstract:
The transmembrane 6 superfamily (TM6SF) comprises two members: TM6SF1, a ubiquitously expressed lysosomal membrane protein of unknown function, and TM6SF2, an endoplasmic reticulum protein required for bulk lipidation of Apolipoprotein B-containing lipoproteins. Here, we used cryo-electron microscopy (cryo-EM) to determine the structure of human TM6SF1 at 2.9-Å resolution. TM6SF1 forms a polytopic homodimer, with each protomer comprising 10 transmembrane helices (TMs). TMs 1-6 form a pocket that accommodates a cholesterol molecule. Cell-based assays revealed that loss of TM6SF1 perturbs mTORC1 signaling, resulting in reduced phosphorylation of S6 kinase 1 and 4E-BP1 and constitutive activation of transcription factor EB (TFEB), and that cholesterol is required for these effects. Biochemical analyses support the model that TM6SF1 directly engages LAMTOR1, a component of Ragulator complex, in a cholesterol-dependent manner. Together, these findings identify TM6SF1 as a lysosomal cholesterol binding protein involved in regulating mTORC1 signaling.
- The Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390.
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