Scavenger receptor class A and Scavenger receptor class B member 1 (SR-A/SR-B1)

Scavenger receptor class A (SR-A, MSR1) and scavenger receptor class B member 1 (SR-B1, SCARB1) are key membrane glycoproteins expressed on macrophages that play critical, yet distinct, roles in lipid metabolism and innate immunity [1, 6, 7]. SR-A is primarily responsible for the endocytic uptake of modified low-density lipoproteins (LDL), such as oxidized or acetylated LDL, which contributes to the formation of lipid-laden foam cells in atherosclerotic plaques [7]. In contrast, SR-B1 serves as a high-affinity receptor for high-density lipoprotein (HDL), mediating the selective uptake of cholesteryl esters and facilitating the efflux of free cholesterol, thereby supporting reverse cholesterol transport and exerting atheroprotective effects [1, 4, 6]. Beyond lipid trafficking, both receptors participate in the immune response; SR-A recognizes a wide array of polyanionic ligands including bacterial components, while SR-B1 is involved in the phagocytosis of apoptotic cells (efferocytosis) and serves as a co-receptor for certain viruses like Hepatitis C [1, 4, 7, 8]. Therapeutic targeting of these receptors is being explored for cardiovascular disease, where SR-B1 activation or SR-A inhibition might reduce plaque progression, and in oncology, where SR-B1 overexpression in certain tumors is leveraged for targeted drug delivery using reconstituted HDL nanoparticles [5, 10, 12]. However, pharmacological modulation faces challenges, such as the potential for SR-B1 inhibition to impair steroidogenesis in the adrenal glands or SR-A deficiency to compromise host defense against infections [1, 4, 7].

Other names

Macrophage scavenger receptor 1MSR1CD204SCARA1Scavenger receptor class B member 1SCARB1CD36L1CLA-1HDL receptor

SR-B1 mediates the selective uptake of cholesteryl esters from HDL and bidirectional flux of free cholesterol between cells and lipoproteins [1, 4], while SR-A mediates the endocytosis of modified low-density lipoproteins (LDL) and the recognition of various polyanionic ligands including bacterial components [7].