Charting the fate of the "good cholesterol": identification and characterization of the high-density lipoprotein receptor SR-BI.
Risk for cardiovascular disease due to atherosclerosis increases with increasing concentrations of low-density lipoprotein (LDL) cholesterol and is inversely proportional to the levels of high-density lipoprotein (HDL) cholesterol. The receptor-mediated control of plasma LDL levels has been well understood for over two decades and has been a focus for the pharmacologic treatment of hypercholesterolemia. In contrast, the first identification and characterization of a receptor that mediates cellular metabolism of HDL was only recently reported. This receptor, called scavenger receptor class B type I (SR-BI), is a fatty acylated glycoprotein that can cluster in caveolae-like domains on the surfaces of cultured cells. SR-BI mediates selective lipid uptake from HDL to cells. The mechanism of selective lipid uptake is fundamentally different from that of classic receptor-mediated endocytic uptake via coated pits and vesicles (e.g. the LDL receptor pathway) in that it involves efficient receptor-mediated transfer of the lipids, but not the outer shell proteins, from HDL to cells. In mice, SR-BI plays a key role in determining the levels of plasma HDL cholesterol and in mediating the regulated, selective delivery of HDL-cholesterol to steroidogenic tissues and the liver. Significant alterations in SR-BI expression can result in cardiovascular and reproductive disorders. SR-BI may play a similar role in humans; thus, modulation of its activity may provide the basis of future approaches to the treatment and prevention of atherosclerotic disease.
Krieger
M
M
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA. krieger@mit.edu
D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D011971:Receptors, Immunologic; D011973:Receptors, LDL / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B
D018955:CD36 Antigens; D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D002784:Cholesterol