Macrophage scavenger receptor 1 (MSR1)

Macrophage scavenger receptor 1 (MSR1), also known as scavenger receptor class A type I (SR-AI) or CD204, is a trimeric integral membrane glycoprotein primarily expressed on the surface of macrophages and dendritic cells [1, 3, 4]. It functions as a pattern recognition receptor with broad ligand specificity, binding polyanionic molecules such as modified low-density lipoproteins (oxLDL and acLDL), bacterial surface components (LPS and LTA), and apoptotic cells [1, 2, 8]. MSR1 plays a critical role in lipid homeostasis by mediating the uptake of modified cholesterol, which can lead to the formation of foam cells in atherosclerotic plaques [1, 8]. Beyond its role in cardiovascular disease, MSR1 is involved in innate immunity, the clearance of amyloid-beta in Alzheimer's disease, and the modulation of the tumor microenvironment through its expression on tumor-associated macrophages [3, 4, 11]. The receptor also influences macrophage polarization, promoting an anti-inflammatory M2-like phenotype that supports tissue repair and tumor progression [1, 15]. Therapeutic strategies targeting MSR1 include its use as a biomarker for M2-like macrophages and the development of ligands for targeted drug delivery or the modulation of inflammatory responses [12, 13, 15]. Research has explored MSR1 as a target for treating atherosclerosis, sepsis, and various cancers, although its dichotomous roles in different diseases present significant therapeutic challenges [3, 11, 13].

Other names

Scavenger receptor class A member 1SR-AICD204SCARA1Macrophage acetylated LDL receptorSRAScvr

MSR1 mediates the binding, internalization, and lysosomal degradation of polyanionic ligands, including modified lipoproteins and pathogens [1, 4, 8]. It also modulates intracellular signaling pathways such as NF-κB and PI3K/AKT, often acting as a co-receptor or negative regulator of Toll-like receptor 4 (TLR4) to influence inflammatory responses and macrophage polarization [1, 11, 15].