The Scavenger Receptor Class B Type I: An HDL Receptor Involved in Lipid Transport and HDL Dependent Signaling

This chapter discusses the significance of the Scavenger Receptor Class B Type I (SR-BI) in high density lipoprotein (HDL) metabolism, atherosclerosis, and coronary heart disease. It also discusses the cellular biology of SR-BI, its activities in lipid transfer between HDL and cells, its role in mediating the activation of cellular signaling pathways by HDL in various cell types, and their possible contribution to atheroprotection. The SR-BI is a palmitylated cell surface glycoprotein that binds HDL and low density lipoproteins (LDL) with high affinity. It was the first molecularly well-defined HDL receptor that was shown to mediate the selective uptake of HDL lipids and HDL-dependent cholesterol efflux from cells. Studies from genetically engineered mice shed light on the role of SR-BI in reverse cholesterol transport, in the protection against atherosclerosis and coronary heart disease. The molecular mechanisms of HDL/SR-BI induced signaling revealed the involvement of numerous pathways that mediate the atheroprotective actions of HDL in cells relevant to atherogenesis such as macrophages, endothelial cells, and vascular smooth muscle cells.