Abstract
Cholesterol is an essential structural component of cellular membranes and serves as a precursor for several classes of signaling molecules. Cholesterol exerts its effects and is, itself, regulated in large part by engagement in specific interactions with proteins. The full complement of sterol-binding proteins that exist in mammalian cells, however, remains unknown. Here we describe a chemoproteomic strategy that uses clickable, photoreactive sterol probes in combination with quantitative mass spectrometry to globally map cholesterol-protein interactions directly in living cells. We identified over 250 cholesterol-binding proteins, including receptors, channels and enzymes involved in many established and previously unreported interactions. Prominent among the newly identified interacting proteins were enzymes that regulate sugars, glycerolipids and cholesterol itself as well as proteins involved in vesicular transport and protein glycosylation and degradation, pointing to key nodes in biochemical pathways that may couple sterol concentrations to the control of other metabolites and protein localization and modification.