Cell Biology

Scavenging Cholesterol

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Science  23 Jan 2004:
Vol. 303, Issue 5657, pp. 435
DOI: 10.1126/science.303.5657.435d

The plasma low-and high-density lipoproteins (LDL and HDL) carry cholesterol that cells use for processes such as membrane and steroid synthesis. Cell surface receptors that capture LDL are internalized, and cholesterol is recovered at a late stage in the endocytic pathway. In contrast, the scavenger receptor BI (SR-BI) that binds HDL does not undergo endocytosis, and the traffic of cholesterol from these serum lipoproteins to cells has not been clear.

Peng et al. observed that SR-BI is present in clusters on microvillar extensions of plasma membrane in a variety of cell types; importantly, SR-BI did not localize to caveolae. Moreover, caveolin-1 was not detected in membrane extensions, and the absence of caveolin-1 in some cell types had no effect on receptor localization.

Detergent solublization analysis indicated that SR-BI is not associated with lipid rafts, which are membrane microdomains where cholesterol is tightly packed with saturated phospholipids in a highly ordered state. The authors propose that SR-BI resides in a more fluid microdomain populated by unsaturated phospholipids and that this disposition favors efficient movement of cholesterol between HDL and the cell membrane. — LDC

Mol. Biol. Cell 15, 384 (2004).

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