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Low Density Lipoprotein Receptor
Definition 1
The low density lipoprotein receptor (LDLR) gene family consists of cell surface proteins involved in receptor-mediated endocytosis of specific ligands. Low density lipoprotein (LDL) is normally bound at the cell membrane and taken into the cell ending up in lysosomes where the protein is degraded and the cholesterol is made available for repression of microsomal enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the rate-limiting step in cholesterol synthesis. At the same time, a reciprocal stimulation of cholesterol ester synthesis takes place. Mutations in this gene cause the autosomal dominant disorder, familial hypercholesterolemia. (NCI Thesaurus/LocusLink)
Definition 2
Receptors on the plasma membrane of nonhepatic cells that specifically bind LDL. The receptors are localized in specialized regions called coated pits. Hypercholesteremia is caused by an allelic genetic defect of three types: 1) receptors do not bind to LDL; 2) there is reduced binding of LDL; and 3) there is normal binding but no internalization of LDL. In consequence, entry of cholesterol esters into the cell is impaired and the intracellular feedback by cholesterol on 3-hydroxy-3-methylglutaryl CoA reductase is lacking. (NLM, Medical Subject Headings)
Definition 3
family of receptors; members include low density lipoprotein receptor, alpha 2-macroglobulin receptor, low density lipoprotein receptor related protein, and kidney proximal tubule membrane protein. (NIH CRISP Thesaurus)
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