SCARB1
Description
The SCARB1 (scavenger receptor class B member 1) is a protein-coding gene located on chromosome 12.
SCARB1, also known as SR-BI, is a protein encoded by the SCARB1 gene in humans. It serves as a receptor for high-density lipoprotein (HDL). SCARB1 is an integral membrane protein found in numerous cell types/tissues, including enterocytes, the liver and adrenal gland. It is primarily known for its role in facilitating the uptake of cholesteryl esters from HDL in the liver. This process drives the movement of cholesterol from peripheral tissues towards the liver, where it can either be secreted via the bile duct or used to synthesize steroid hormones. This movement of cholesterol is known as reverse cholesterol transport and is a protective mechanism against the development of atherosclerosis, the primary cause of heart disease and stroke. SCARB1 is crucial in carotenoid and vitamin E uptake in the small intestine. It is upregulated during vitamin A deficiency and downregulated when vitamin A levels are normal. In melanocytic cells, SCARB1 gene expression may be regulated by MITF. SR-BI has also been identified in the livers of non-mammalian species (turtle, goldfish, shark, chicken, frog, and skate), suggesting its emergence early in vertebrate evolutionary history. Turtles also seem to upregulate SR-BI during egg development, indicating that cholesterol efflux may be at peak levels during developmental stages.
SCARB1 is a receptor for various ligands including phospholipids, cholesterol esters, lipoproteins, phosphatidylserine, and apoptotic cells. It acts as a receptor for HDL, facilitating selective uptake of cholesteryl ether and HDL-dependent cholesterol efflux. It also facilitates the flux of free and esterified cholesterol between the cell surface and apoB-containing lipoproteins and modified lipoproteins, though less efficiently than HDL. SCARB1 might be involved in the phagocytosis of apoptotic cells through its phosphatidylserine binding activity.
SCARB1 is also known as CD36L1, CLA-1, CLA1, HDLCQ6, HDLQTL6, SR-BI, SRB1.
