Regulation of autophagosome biogenesis and mitochondrial bioenergetics by the cholesterol transport protein GRAMD1C

ABSTRACTAutophagosomes are crucial components of the cellular recycling machinery that form at endoplasmic reticulum (ER)-associated sites. As the autophagosome membrane is largely devoid of transmembrane proteins, autophagosome biogenesis is thought to be largely regulated by lipid transfer and lipid modifications, as well as membrane-associated proteins. While the membrane origin of autophagosomes and their lipid composition are still incompletely understood, previous studies have found the autophagosome membrane to be enriched in unsaturated fatty acids and have little cholesterol, suggesting that cholesterol removal is an integral step during autophagosome biogenesis. In our study, we demonstrate that short term cholesterol depletion leads to a rapid induction of autophagy and identify the ER-localized cholesterol transport protein GRAMD1C as a negative regulator of starvation-induced macroautophagy/autophagy. Abbreviations: ATG: autophagy related; ccRCC: clear cell renal cell carcinoma; ER: endoplasmic reticulum; GRAM: glucosyltransferases, RAB-like GTPase activators and myotubularins; GRAMD: GRAM domain containing; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCBD: methyl-cyclodextrin; MTOR: mechanistic target of rapamycin kinase; VASt: VAD1 analog of StAR-related lipid transfer.KEYWORDS: AsterautophagyccRCCcholesterolGRAMD1CVASt AcknowledgmentsWe would like to thank the other co-authors who contributed to the original manuscript; Ana Lapao, Sakshi Singh, Laura Trachsel-Moncho, Sebastian W. Schultz, Sigve Nakken and Michael J. Munson. This work was funded by the Research Council of Norway through its Centres of Excellence funding scheme (Project: 262652) and FRIPRO grants (Project: 249753 and 314684) and by the Norwegian Cancer Society (Project: 171318).Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by the Research Council of Norway [262652, 249753 and 314684]; Norwegian Cancer Society [171318].