Chemical biology of intracellular cholesterol transport

Cholesterol transport proteins (CTPs) regulate cellular metabolism, hormone biosynthesis, and organelle contacts, with profound consequences for human health and disease. Despite this, almost no small molecule CTP modulators have been reported, and no methods for determining selectivity across the broader protein class exist. Selective CTP inhibition is conceptually challenging as all CTPs are structurally similar and bind cholesterol. Furthermore, due to redundancy among several CTPs, deciphering the biological roles of their individual cholesterol transport activity has been difficult. ChemBioChol aims to unravel the functions of individual CTPs by developing selective small molecule modulators. Based on seminal work from my lab, I propose employing a sterol-inspired compound design strategy consisting of a primary sterol fragment as “anchor” for CTP binding, fused to secondary natural product fragments to engineer selectivity of the compounds for individual CTPs. My group will develop bio-physical and -chemical tools to determine lipid selectivity of CTPs and optimise selective molecules against them. Preliminary data on the Aster CTP family provides a proof-of-principle that selective and potent chemical tools are attainable, and that the concept is applicable to further CTP families. To determine cellular selectivity of CTP inhibitors against all cholesterol-binding proteins, I will also develop a mass spectrometry-based chemical proteomic approach with a universal cholesterol probe. Optimised CTP inhibitors will be used to determine how CTPs mediate lipid metabolism and trafficking, and their effect on sterol-mediated processes including mTOR signaling and autophagy, with potential applications in neurodegenerative disorders and cancer. A general approach for selectively modulating CTPs is ground-breaking and will have impact beyond this set of proteins by providing a blueprint for studying and targeting other families of lipid-binding proteins in the future.