scavenger receptor A
Summary
Macrophage surface receptor (SR-A) that binds and internalizes modified (oxidized/acetylated) LDL and a variety of polyanionic ligands. Central to foam cell formation in atherosclerosis and to pattern recognition in innate immunity.
Detail
Unlike the classic LDL receptor, scavenger receptor A is not downregulated by intracellular cholesterol, so macrophages keep ingesting oxidized LDL until they become lipid-laden foam cells, the hallmark of the fatty streak. SR-A also recognizes microbial components (lipoteichoic acid, LPS, bacterial CpG DNA) and apoptotic cells, contributing to innate immune clearance. Expression is induced on macrophages and is shared with related family members (CD36, LOX-1) that have overlapping roles in atherogenesis. High-yield boards link: 'why doesn't cholesterol shut off foam cell formation?' - because uptake is via scavenger receptors, not the regulated LDL receptor.
Sources
- First Aid for USMLE Step 1 2024
- Robbins Basic Pathology 10th ed
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