title: Cholesterol trafficking is required for mTOR activation in endothelial cells.
abstract: Mammalian target of rapamycin (mTOR) constitutes a nodal point of a signaling network that regulates cell growth and proliferation in response to various environmental cues ranging from growth factor stimulation to nutrients to stress. Whether mTOR is also affected by cholesterol homeostasis, however, has remained unknown. We report that blockade of cholesterol trafficking through lysosome by a newly identified inhibitor of angiogenesis, itraconazole, leads to inhibition of mTOR activity in endothelial cells. Inhibition of mTOR by itraconazole but not rapamycin can be partially restored by extracellular cholesterol delivered by cyclodextrin. Moreover, other known inhibitors of endosomal/lysosomal cholesterol trafficking as well as siRNA knockdown of Niemann-Pick disease type C (NPC) 1 and NPC2 also cause inhibition of mTOR in endothelial cells. In addition, both the accumulation of cholesterol in the lysosome and inhibition of mTOR caused by itraconazole can be reversed by thapsigarin. These observations suggest that mTOR is likely to be involved in sensing membrane sterol concentrations in endothelial cells, and the cholesterol trafficking pathway is a promising target for the discovery of inhibitors of angiogenesis.
authors.affiliation: Department of Pharmacology and Oncology, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Dang
authors.forename: Yunzhao R
authors.initials: YR
authors.lastname: Ren
authors.forename: Jun O
authors.initials: JO
authors.lastname: Liu
mesh_terms: D000736:Androstenes / Q000494:pharmacology; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D003505:Cyclodextrins / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007099:Imipramine / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D017964:Itraconazole / Q000494:pharmacology; D000076222:Mechanistic Target of Rapamycin Complex 1; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes; D000077296:Niemann-Pick C1 Protein; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins; D034622:RNA Interference; D058570:TOR Serine-Threonine Kinases; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D000736:Androstenes; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D003505:Cyclodextrins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D011506:Proteins; D014157:Transcription Factors; D050760:Cyclin-Dependent Kinase Inhibitor p27; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D017964:Itraconazole; D019284:Thapsigargin; D002784:Cholesterol; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D007099:Imipramine