Lysosomal regulation of cholesterol homeostasis in tuberous sclerosis complex is mediated via NPC1 and LDL-R

// Harilaos Filippakis 1 , Nicola Alesi 1 , Barbara Ogorek 1 , Julie Nijmeh 1 , Damir Khabibullin 1 , Catherine Gutierrez 1 , Alexander J. Valvezan 2 , James Cunningham 3 , Carmen Priolo 1 and Elizabeth P. Henske 1 1 Division of Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA 2 Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts, USA 3 Department of Medicine, Division of Hematology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA Correspondence to: Elizabeth P. Henske, email: // Keywords : TSC, mTORC1, chloroquine, cholesterol, lysosome Received : February 25, 2017 Accepted : April 15, 2017 Published : April 27, 2017 Abstract Tuberous sclerosis complex (TSC) is a multisystem disease associated with hyperactive mTORC1. The impact of TSC1/2 deficiency on lysosome-mediated processes is not fully understood. We report here that inhibition of lysosomal function using chloroquine (CQ) upregulates cholesterol homeostasis genes in TSC2-deficient cells. This TSC2-dependent transcriptional signature is associated with increased accumulation and intracellular levels of both total cholesterol and cholesterol esters. Unexpectedly, engaging this CQ-induced cholesterol uptake pathway together with inhibition of de novo cholesterol synthesis allows survival of TSC2-deficient, but not TSC2-expressing cells. The underlying mechanism of TSC2-deficient cell survival is dependent on exogenous cholesterol uptake via LDL-R, and endosomal trafficking mediated by Vps34. Simultaneous inhibition of lysosomal and endosomal trafficking inhibits uptake of esterified cholesterol and cell growth in TSC2-deficient, but not TSC2-expressing cells, highlighting the TSC-dependent lysosome-mediated regulation of cholesterol homeostasis and pointing toward the translational potential of these pathways for the therapy of TSC.