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Beschreibung

Scavenger receptor class B member 1 (UniProt: Q61009, also known as SRB1, SR-BI) is encoded by the Scarb1 (also known as Srb1) gene (Gene ID: 20778) in murine species. SR-BI (SCARB1) is a widely expressed, multi-pass membrane glycoprotein with two cytoplasmic domains (aa 1-11 and 462-509), one extracellular domain (aa 33-440) and two transmembrane domains (aa 12-32 and 441-461). It serves as a receptor for several different ligands such as phospholipids, cholesterol ester, lipoproteins, and phosphatidylserine. It is a key component in the reverse cholesterol transport pathway and thus plays an important role in lipid metabolism. It may also contribute to variations in plasma lipid levels during fasting. Two isoforms of SR-BI have been described that are produced by alternative splicing and both isoforms can serve as a receptor for HDL and mediate selective uptake of cholesteryl ether and HDL-dependent cholesterol efflux. It is reported to facilitate the flux of free and esterified cholesterol between the cell surface and ApoB-containing lipoproteins and modified lipoproteins, although less efficiently than HDL. SR-BI is also involved in phagocytosis of apoptotic cells, via its phosphatidylserine binding activity. Elevated expression of SR-BI has been reported in a wide variety of malignant cell lines such as breast, prostate, ovarian, pancreatic, nasopharyngeal, and colorectal cancers. In hepatocytes, it is reported to act as a receptor for hepatitis C virus and facilitates virus entry into cells. SR-B1 is also described as a silica receptor that through an extracellular -helix specifically recognizes amorphous and crystalline silica. However, it does not recognize titanium dioxide nanoparticles, latex nanoparticles, or monosodium urate crystals. It is involved in silica-induced pulmonary inflammation in murine models. Clone AOB-1 is shown to specifically bind to murine SR-BI on Jurkat.EcoR cells and blocks silica binding to these cells in a dose-dependent manner. (Ref.: Tsugita, M., et al. (2017). Cell Rep. 18, 1298-1311, Mooberry, LK., et al. (2016). Front. Pharmacol. 7, 466). Webb, NR., et al. (1998). J. Biol. Chem. 273(24), 15241-15248).