@article{a2b430aeaa404436a686ef5244a422b2,
title = "Scap structures highlight key role for rotation of intertwined luminal loops in cholesterol sensing",
abstract = "The cholesterol-sensing protein Scap induces cholesterol synthesis by transporting membrane-bound transcription factors called sterol regulatory element-binding proteins (SREBPs) from the endoplasmic reticulum (ER) to the Golgi apparatus for proteolytic activation. Transport requires interaction between Scap's two ER luminal loops (L1 and L7), which flank an intramembrane sterol-sensing domain (SSD). Cholesterol inhibits Scap transport by binding to L1, which triggers Scap's binding to Insig, an ER retention protein. Here we used cryoelectron microscopy (cryo-EM) to elucidate two structures of full-length chicken Scap: (1) a wild-type free of Insigs and (2) mutant Scap bound to chicken Insig without cholesterol. Strikingly, L1 and L7 intertwine tightly to form a globular domain that acts as a luminal platform connecting the SSD to the rest of Scap. In the presence of Insig, this platform undergoes a large rotation accompanied by rearrangement of Scap's transmembrane helices. We postulate that this conformational change halts Scap transport of SREBPs and inhibits cholesterol synthesis.",
keywords = "Golgi apparatus, Insig, SREBP, Scap, cholesterol, cryo-electron microscopy, endoplasmic reticulum, lipid metabolism, membrane homeostasis",
author = "Kober, {Daniel L.} and Arun Radhakrishnan and Goldstein, {Joseph L.} and Brown, {Michael S.} and Clark, {Lindsay D.} and Bai, {Xiao chen} and Rosenbaum, {Daniel M.}",
note = "Funding Information: We are grateful to Linda Donnelly and Angela Carroll for antibody production; Lisa Beatty, Karen Chapman, Ije Dukes, Bilkish Bajaj, and Camille Harry for assistance with cell culture and baculovirus production; Yinxin Zhang and Kwang-min Lee for characterization of the disulfide bond in Scap; and Shimeng Xu for assistance with transfection experiments. This project was supported by the National Institutes of Health (R35GM136387 to D.M.R.; P01HL20948 to A.R. M.S.B. and J.L.G.; and R01GM136976 to X.-c.B.), the Welch Foundation (I-1770 to D.M.R. I-1793 to A.R. and I-1944 to X.-c.B.), a Mallinckrodt Foundation scholar award (to D.M.R.), Fondation Leducq (19CVD04 to A.R.), and CPRIT (RR160082 to X.-c.B.). D.L.K. is a recipient of a postdoctoral fellowship from the American Heart Association (18POST34080141). Cryo-EM data were collected at the University of Texas Southwestern Medical Center Cryo-EM Facility, which is funded by CPRIT core facility support award RP170644. D.L.K. A.R. J.L.G. M.S.B. L.D.C. X.-c.B. and D.M.R. designed the research. D.L.K. A.R. L.D.C. X.-c.B. and D.M.R. performed the research. D.L.K. A.R. J.L.G. M.S.B. L.D.C. X.-c.B. and D.M.R. analyzed the data. D.L.K. A.R. J.L.G. M.S.B. X.-c.B. and D.M.R. wrote the paper. The authors declare no competing interests. Funding Information: We are grateful to Linda Donnelly and Angela Carroll for antibody production; Lisa Beatty, Karen Chapman, Ije Dukes, Bilkish Bajaj, and Camille Harry for assistance with cell culture and baculovirus production; Yinxin Zhang and Kwang-min Lee for characterization of the disulfide bond in Scap; and Shimeng Xu for assistance with transfection experiments. This project was supported by the National Institutes of Health ( R35GM136387 to D.M.R.; P01HL20948 to A.R., M.S.B., and J.L.G.; and R01GM136976 to X.-c.B.), the Welch Foundation ( I-1770 to D.M.R., I-1793 to A.R., and I-1944 to X.-c.B.), a Mallinckrodt Foundation scholar award (to D.M.R.), Fondation Leducq ( 19CVD04 to A.R.), and CPRIT ( RR160082 to X.-c.B.). D.L.K. is a recipient of a postdoctoral fellowship from the American Heart Association ( 18POST34080141 ). Cryo-EM data were collected at the University of Texas Southwestern Medical Center Cryo-EM Facility, which is funded by CPRIT core facility support award RP170644 . Publisher Copyright: {\textcopyright} 2021 Elsevier Inc.",
year = "2021",
month = jul,
day = "8",
doi = "10.1016/j.cell.2021.05.019",
language = "English (US)",
volume = "184",
pages = "3689--3701.e22",
journal = "Cell",
issn = "0092-8674",
publisher = "Cell Press",
number = "14",
}