|Detection of SR‑AI/MSR in RAW 264.7 Mouse Cell Line by Flow Cytometry. RAW 264.7 mouse monocyte/macrophage cell line was stained with Rat Anti-Mouse SR‑AI/MSR Fluorescein‑conjugated Monoclonal Antibody (Catalog # FAB1797F, filled histogram) or isotype control antibody (Catalog # IC013F, open histogram). View our protocol for Staining Membrane-associated Proteins.|
The Scavenger Receptor (SR) family comprises a group of functionally defined membrane receptors that share the common ability to bind and internalize modified forms of Low Density Lipoproteins (mLDL) (1‑3). Family members are classified alphabetically. The A class includes four proteins: the three subtypes of SR-A (AI, AII, and AIII) that are generated by alternative splicing of the same gene, and a structurally similar protein named MARCO (4). All A class SRs are multidomain, trimeric type II trans-membrane proteins. SR-AI has an N-terminal cytoplasmic domain, a transmembrane domain, a spacer domain, an alpha -helical coiled coil, a collagen-like domain and a C-terminal cysteine-rich domain. SR-A is expressed by most tissue macrophages, dendritic cells and Kupffer cells. It is also highly expressed by microglia in neonatal as well as Alzheimer’ Disease brains. SR-AI binds a broad range of polyanionic ligands including modified proteins (e.g. oxidized, acetylated or maleylated LDL, advanced glycation end-product proteins), polyribonucleotides (polyguanosine and polyinosine), polysaccharides (dextran sulfate, fucoidan), phospholipids (phosphatidylserine), bacterial products (lipopolysaccharide and lipoteichoic acid) and selected chemical compounds (silica, crocidolite asbestos). The ligand-binding region has been localized to a positively charged region in the carboxyl end of the collagen-like domain. Based on its ligand binding characteristics, SR-AI is implicated in many physiological and pathophysiological functions. Studies using SR-A knockout mouse have also suggested roles of SR-A in atherogenesis, host defense and innate immunity, acquired immune responses, macrophage adhesion, and phagocytosis of apoptotic cells (1‑3). Over aa 83-458, mouse and human SR-AI share 71% amino acid sequence identity.