CD36 (also known as platelet glycoprotein 4) is a recognition receptor that binds polyanionic ligands of both pathogen and self-origin, and is implicated in the pathogenesis of atherosclerosis and Alzheimer's disease [, ]. CD36 plays an important role in innate immunity and in the phagocytic uptake of multiple pathogens including malaria []. It has also been implicated in several aspects related to fatty acid metabolism [].Mutations in the CD36 gene cause platelet glycoprotein IV deficiency (PG4D), a disorder characterised by macrothrombocytopenia without notable hemostatic problems and bleeding tendency [, ].
This entry includes CD36 and CD36-like proteins, including SCARB1/2 from vertebrates and SNMP1/2 from flies. CD36 is a transmembrane, highly glycosylated, 88kDa glycoprotein expressed by monocytes, macrophages, platelets, microvascular endothelial cells and adipose tissues. Platelet glycoprotein IV (GP IV)(GPIIIb) (CD36 antigen) is also called GPIV, OKM5-antigen or PASIV. CD36 recognises oxidized low density lipoprotein, long chain fatty acids, anionic phospholipids, collagen types I, IV and V, thrombospondin (TSP) and Plasmodium falciparum infected erythrocytes. The recognition of apoptotic neutrophils is in co-operation with TSP and avb3. Other ligands may still be unknown.CD36 is a scavenger receptor for oxidized LDL and shed photoreceptor outer segments and in recognition and phagocytosis of apoptotic cells and is the cell adhesion molecule in platelet adhesion and aggregation, platelet-monocyte and platelet-tumor cell interaction [].
This entry includes platelet glycoprotein 4 (CD36) and scavenger receptor class B member 1 (SCARB1, also known as CD36 antigen-like 1) from humans, and sensory neuron membrane protein 1 (SNMP1) from flies. CD36 is a a scavenger receptor important for lipoprotein binding and uptake of cholesterol and lipids in vertebrates []. SCARB1 plays an important role in the uptake of HDL cholesteryl ester []. It acts as a receptor for hepatitis C virus in hepatocytes [].SNMP1 is a homologue of CD36. SNMP1 has a role in detection and signal transduction of the fatty-acid-derived male pheromone 11-cis vaccenyl acetate (cVA) [].
Lysosome membrane protein II (LIMP II) is a 478-residue glycoproteinexpressed in the membrane of lysosomes and secretory granules with lysosomalproperties []. The N-terminal segment (residues ~4-26) constitutes an uncleavable signal peptide []. LIMP II possesses an additional C-terminalhydrophobic region that, together with the signal peptide, may anchor theprotein to the membrane []. The major portion of the protein resides ontheluminal side and contains 11 potential N-glycosylation sites and 5 cysteineresidues. The N- and C-terminal ends of the protein constitute short cytoplasmic tails. LIMP II is a subgroup of a larger family of the cell surface protein CD36 involved in cell adhesion.
Thrombospondin 1 (TSP-1) is a member of the thrombospondin (TSP) family, which consists of five extracellular calcium-binding multifunctional proteins: TSP-1, TSP-2, TSP-3, TSP-4, and TSP-5. TSP-1 is involved in angiogenesis, cancer, and inflammation. It is a major activator of transforming growth factor (TGFbeta1), which mediates wound healing, cell proliferation, extracellular matrix formation, and the immune response [].TSP-1 is a large, homotrimeric molecule. Each monomer consists of an N-terminal globular domain that binds heparin, type I, type II, and type III repeats, and a C-terminal globular domain. All five members of the TSP family have the repeat domains type II and III, but only TSP-1 and TSP-2 contain the type I repeats []. TSP-1-specific domains bind to proteoglycans, membrane proteins such as integrins, and other matrix proteins expressed by a variety of cells [, ]. Type I repeats, also called thrombospondin structural homology repeats (TSRs), inhibit angiogenesis by activating CD36 and inducing apoptosis in endothelial cells [].
