Scavenger receptor class A member 1 (MSR1) (SR-A1)

Scavenger receptor class A member 1 (SR-A1), also known as MSR1 or CD204, is a homotrimeric type II transmembrane glycoprotein primarily expressed on the surface of macrophages and dendritic cells (UniProt P21757). It serves as a major pattern recognition receptor (PRR) that identifies and internalizes a diverse range of polyanionic ligands, including oxidized low-density lipoproteins (oxLDL), bacterial surface components, and apoptotic cell debris (PubMed: 25631234). In the context of cardiovascular disease, SR-A1 is a central mediator of atherosclerosis, as its unregulated uptake of oxLDL leads to the formation of lipid-laden foam cells within the arterial wall (PubMed: 12490658). Beyond lipid metabolism, SR-A1 plays a complex role in the immune system by facilitating pathogen clearance and modulating inflammatory cytokine production. In oncology, high expression of SR-A1 is a hallmark of M2-polarized tumor-associated macrophages (TAMs), which promote an immunosuppressive microenvironment and support tumor growth and metastasis (PubMed: 28652333). While no FDA-approved drugs currently target SR-A1, it is being actively investigated as a target for nanoparticle-based drug delivery and as a potential checkpoint for reprogramming the immune response in chronic inflammatory diseases and cancer.

Other names

Macrophage scavenger receptor 1CD204SCARA1SR-AMacrophage scavenger receptor types I and IIMSR

Binding and internalization of polyanionic ligands through receptor-mediated endocytosis, leading to the clearance of modified lipids, pathogens, or cellular debris, and the subsequent modulation of intracellular signaling pathways such as TLR4 and NF-kappaB.