CD36
Encyclopedia
CD36 is an integral membrane protein
found on the surface of many cell types in vertebrate animals and is also known as FAT, SCARB3, GP88, glycoprotein IV (gpIV) and glycoprotein IIIb (gpIIIb). CD36 is a member of the class B scavenger receptor
family of cell
surface proteins. CD36 binds many ligands
including collagen
, thrombospondin
, erythrocytes parasitized with Plasmodium falciparum
, oxidized low density lipoprotein
, native lipoproteins, oxidized phospholipids, and long-chain fatty acid
s.
Recent work using genetically modified rodents have identified a clear role for CD36 in fatty acid
and glucose
metabolism, heart disease
, taste, and dietary fat processing in the intestine
. It may be involved in glucose intolerance, atherosclerosis
, arterial hypertension
, diabetes, cardiomyopathy
and Alzheimer's disease
.
. However, CD36 is extensively glycosylated and has an apparent molecular weight of 88,000 Da
as determined by SDS polyacrylamide gel electrophoresis
.
of CD36 predicts a hydrophobic region near each end of the protein large enough to span cellular membrane
s. Based on this notion and the observation that CD36 is found on the surface of cells, CD36 is thought to have a 'hairpin-like' structure with α-helices
at the C- and N- termini projecting through the membrane
and a larger extracellular loop (Fig. 1). This topology
is supported by transfection experiments in cultured cells using deletion mutants of CD36.
Unlike the topology and proposed structure of transmembrane α-helices
, very little is known about the secondary structure
of the extracellular loop. Disulfide linkages between 4 of the 6 cysteine
residues in the extracellular loop are required for efficient intracellular processing and transport of CD36 to the plasma membrane. It is not clear what role these linkages play on the function of the mature CD36 protein on the cell surface.
s have been reported for CD36. CD36 is modified with 4 palmitoyl chains, 2 on each of the two intracellular domains. The function of these lipid modifications is currently unknown but they likely promote the association of CD36 with the membrane and possibly lipid rafts which appear to be important for some CD36 functions.
.
is located on the long arm of chromosome
7 at band 11.2 (7q11.2) and is encoded by 15 exon
s that extend over more than 32 kilobases. Both the 5' and the 3' untranslated regions contain intron
s: the 5' with two and the 3' one. Exons 1, 2 and first 89 nucleotides of exon 3 and as well as exon 15 are non-coding. Exon 3 contains encodes the N-terminal cytoplasmic and transmembrane domains. The C-terminal cytoplasmic and transmembrane regions is encoded by exon 14. The extracellular domain is encoded by the central 11 exons. Alternative splicing of the untranslated regions gives rise to at least two mRNA species.
The transcription
initiation site of the CD36 gene has been mapped to 289 nucleotide
s upstream from the translational start codon and a TATA box
and several putative cis regulatory regions lie further 5'. A binding site for PEBP2/CBF factors has been identified between -158 and -90 and disruption of this site reduces expression. The gene is the transcriptional control of the nuclear
receptor
PPAR/RXR heterodimer (Peroxisome proliferator-activated receptor
– Retinoid X receptor
) and gene expression can be up regulated using synthetic and natural ligands for PPAR and RXR, including the thiazolidinedione
class of anti-diabetic drugs
and the vitamin A
metabolite 9-cis-retinoic acid
respectively.
s, erythrocytes, monocyte
s, differentiated adipocyte
s, mammary epithelial cells, spleen
cells and some skin
microdermal endothelial cells.
family which includes receptor for selective cholesteryl ester uptake, scavenger receptor class B type I
(SR-BI), and lysosomal integral membrane protein II
(LIMP-II). CD36 interacts with a number of ligands, including collagen
types I and IV, thrombospondin
, erythrocytes parasitized with Plasmodium falciparum
, platelet-agglutinating protein p37, oxidized low density lipoprotein
and long-chain fatty acids. On macrophages CD36 forms part of a non opsonic receptor (the scavenger receptor CD36/alphaV beta3 complex) and is involved in phagocytosis. CD36 has also been implicated in hemostasis
, thrombosis
, malaria
, inflammation
, lipid
metabolism
and atherogenesis.
On binding a ligand the protein and ligand are internalized. This internalization is independent of macropinocytosis and occurs by an actin dependent mechanism requiring the activation Src-family kinases, JNK and Rho-family GTPases. Unlike macropinocytosis this process is not affected by inhibitors of phosphatidylinositol 3-kinase or Na+/H+ exchange.
CD36 ligands have also been shown to promote sterile inflammation through assembly of a Toll-like receptor
4 and 6 heterodimer.
Recently, CD36 was linked to store-operated calcium flux, phospholipase A2 activation, and production of prostaglandin E2
are characterized by sequestration of erythrocytes infected with mature forms of the parasite and CD36 has been shown to be a major sequestration receptor on microvascular endothelial cells. Parasitised erythrocytes adhere to endothelium at the trophozoite/schizonts stage simultaneous with the appearance of the var gene product (erythrocyte membrane protein 1) on the erythrocyte surface. The appearance of erythrocyte membrane protein 1 (PfEMP1) on the erythrocyte surface is a temperature
dependent phenomenon which is due to increased protein trafficking to the erythrocyte surface at the raised temperature. PfEMP1 can bind other endothelial receptors - thrombospondin
(TSP) and intercellular adhesion molecule 1 (ICAM-1
) – in addition to CD36 - and genes other than PfEMP1 also bind to CD36: cytoadherence linked protein (clag) and sequestrin. The PfEMP1 binding site on CD36 is known to be located on exon 5.
CD36 on the surface of the platelets has been shown to be involved in adherence but direct adherence to the endothelium by the infected erythrocytes also occurs. Autoaggregation of infected erythrocytes by platelets has been shown to correlate with severe malaria and cerebral malaria in particular and antiplatelet antibodies may offer some protection.
Several lines of evidence suggest that mutations in CD36 are protective against malaria: mutations in the promoters and within introns and in exon 5 reduce the risk of severe malaria. Gene diversity studies suggest there has been positive selection on this gene presumably due to malarial selection pressure. Dissenting reports are also known
suggesting that CD36 is not the sole determinant of severe malaria. In addition a role for CD36 has been found in the clearance of gametocyte
s (stages I and II).
CD36 has been shown to have a role in the innate immune response to malaria in mouse models. Compared with wild type mice CD36 (-/-) mice the cytokine induction response and parasite clearance were impaired. Earlier peak parasitemias, higher parasite densities and higher mortality were noted. It is thought that CD36 is involved in the Plasmodium falciparum
glycophosphatidylinositol
(PfGPI) induced MAPK activation and proinflammatory cytokine secretion. When macrophages were exposed to PfGPI the proteins ERK1/2, JNK, p38, and c-Jun became phosphorylated. All these proteins are involved as secondary messengers in the immune response. These responses were blunted in the CD36 (-/-) mice. Also in the CD36 (-/-) macrophages secreted significantly less TNF-alpha on exposure to PfGPI. Work is ongoing to determine how these exactly how these responses provide protection against malaria.
antigen
. The Naka null phenotype
is found in 0.3% of Caucasians and appears to be asymptomatic. The null phenotype is more common in Africa
n (2.5%), Japan
ese, and other Asia
n populations (5-11%).
Mutations in the human CD36 gene were first identified in a patient who, despite multiple platelet
transfusions, continued to exhibit low platelet levels. This condition is known as refractoriness to platelet transfusion. Subsequent studies have shown that CD36 found on the surface of platelets. This antigen is recognized by the monoclonal antibodies
(MAbs) OKM5 and OKM8. It is bound by the Plasmodium falciparum
protein sequestrin.
Depending on the nature of the mutation in codon 90 CD36 may be absent either on both platelets and monocytes (type 1) or platelets alone (type 2). Type 2 has been divided in to two subtypes - a and b. Deficiency restricted to the platelets alone is known as type 2a; if CD36 is also absent from the erythoblasts the phenotype is classified as type 2b. The molecular basis is known for some cases: T1264G in both Kenya
ns and Gambians; C478T (50%), 539 deletion of AC and 1159 insertion of an A, 1438-1449 deletion and a combined 839-841 deletion GAG and insertion of AAAAC in Japanese.
In a study of 827 apparently healthy Japanese volunteers, type I and II deficiencies were found in 8 (1.0%) and 48 (5.8%) respectively. In 1127 healthy French blood donors (almost all of whom were white Europeans) no CD36 deficiency was found. In a second group only 1 of 301 white test subjects was found to be CD36 deficient. 16 of the 206 sub-Saharan black Africans and 1 of 148 black Caribbeans were found to be CD36 -ve. Three of 13 CD36 -ve persons examined had anti CD36 antibodies. In a group of 250 black American blood donors 6 (2.4%) were found to be Naka antigen negative.
CD36 deficiency may be a cause of post transfusion purpura
.
and CD36 but this needs to be confirmed.
s related to CD36 are SCARB1
and SCARB2
proteins.
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...
found on the surface of many cell types in vertebrate animals and is also known as FAT, SCARB3, GP88, glycoprotein IV (gpIV) and glycoprotein IIIb (gpIIIb). CD36 is a member of the class B scavenger receptor
Scavenger receptor
Scavenger receptors are a group of receptors that recognize modified low-density lipoprotein by oxidation or acetylation. This naming is based on a function of cleaning : Scavenger receptors widely recognize and uptake macromolecules having a negative charge as well as modified LDL.-Function:It is...
family of cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
surface proteins. CD36 binds many ligands
Protein ligands
In biochemistry, a protein ligand is an atom, a molecule or an ion which can bind to a specific site on a protein. Alternative names used to mean a protein ligand are affinity reagents or protein binders...
including collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, thrombospondin
Thrombospondin
Thrombospondins are secreted proteins with antiangiogenic abilities. TSP was discovered by Nancy L. Baenziger.-Types:The thrombospondins are a family of multifunctional proteins...
, erythrocytes parasitized with Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
, oxidized low density lipoprotein
Low density lipoprotein
Low-density lipoprotein is one of the five major groups of lipoproteins, which in order of size, largest to smallest, are chylomicrons, VLDL, IDL, LDL, and HDL, that enable transport of cholesterol within the water-based bloodstream...
, native lipoproteins, oxidized phospholipids, and long-chain fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
s.
Recent work using genetically modified rodents have identified a clear role for CD36 in fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
and glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
metabolism, heart disease
Heart disease
Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
, taste, and dietary fat processing in the intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
. It may be involved in glucose intolerance, atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
, arterial hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, diabetes, cardiomyopathy
Cardiomyopathy
Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...
and Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
.
Primary
In humans, rats and mice, CD36 consists of 472 amino acids with a predicted molecular weight of approximately 53,000 DaAtomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
. However, CD36 is extensively glycosylated and has an apparent molecular weight of 88,000 Da
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
as determined by SDS polyacrylamide gel electrophoresis
SDS-PAGE
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques widely used in biochemistry, forensics, genetics and molecular biology to separate proteins according to their electrophoretic mobility...
.
Tertiary
Using Kyte-Doolittle analysis, the amino acid sequencePeptide sequence
Peptide sequence or amino acid sequence is the order in which amino acid residues, connected by peptide bonds, lie in the chain in peptides and proteins. The sequence is generally reported from the N-terminal end containing free amino group to the C-terminal end containing free carboxyl group...
of CD36 predicts a hydrophobic region near each end of the protein large enough to span cellular membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
s. Based on this notion and the observation that CD36 is found on the surface of cells, CD36 is thought to have a 'hairpin-like' structure with α-helices
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
at the C- and N- termini projecting through the membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
and a larger extracellular loop (Fig. 1). This topology
Membrane topology
In biochemistry, the membrane topology of an transmembrane protein describes which portions of the amino-acid sequence of the protein lie within the plane of the surrounding lipid bilayer and which portions protrude into the watery environment on either side...
is supported by transfection experiments in cultured cells using deletion mutants of CD36.
Unlike the topology and proposed structure of transmembrane α-helices
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
, very little is known about the secondary structure
Secondary structure
In biochemistry and structural biology, secondary structure is the general three-dimensional form of local segments of biopolymers such as proteins and nucleic acids...
of the extracellular loop. Disulfide linkages between 4 of the 6 cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
residues in the extracellular loop are required for efficient intracellular processing and transport of CD36 to the plasma membrane. It is not clear what role these linkages play on the function of the mature CD36 protein on the cell surface.
Posttranslational modification
Besides glycosylation, additional posttranslational modificationPosttranslational modification
Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins....
s have been reported for CD36. CD36 is modified with 4 palmitoyl chains, 2 on each of the two intracellular domains. The function of these lipid modifications is currently unknown but they likely promote the association of CD36 with the membrane and possibly lipid rafts which appear to be important for some CD36 functions.
Protein-protein interactions
In the absence of ligand, membrane bound CD36 exists primarily in a monomeric state. However exposure to the thrombospondin ligand causes CD36 to dimerize. This dimerization has been proposed to play an important role in CD36 signal transductionSignal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
.
Genetics
The geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
is located on the long arm of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
7 at band 11.2 (7q11.2) and is encoded by 15 exon
Exon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
s that extend over more than 32 kilobases. Both the 5' and the 3' untranslated regions contain intron
Intron
An intron is any nucleotide sequence within a gene that is removed by RNA splicing to generate the final mature RNA product of a gene. The term intron refers to both the DNA sequence within a gene, and the corresponding sequence in RNA transcripts. Sequences that are joined together in the final...
s: the 5' with two and the 3' one. Exons 1, 2 and first 89 nucleotides of exon 3 and as well as exon 15 are non-coding. Exon 3 contains encodes the N-terminal cytoplasmic and transmembrane domains. The C-terminal cytoplasmic and transmembrane regions is encoded by exon 14. The extracellular domain is encoded by the central 11 exons. Alternative splicing of the untranslated regions gives rise to at least two mRNA species.
The transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
initiation site of the CD36 gene has been mapped to 289 nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s upstream from the translational start codon and a TATA box
TATA box
The TATA box is a DNA sequence found in the promoter region of genes in archaea and eukaryotes; approximately 24% of human genes contain a TATA box within the core promoter....
and several putative cis regulatory regions lie further 5'. A binding site for PEBP2/CBF factors has been identified between -158 and -90 and disruption of this site reduces expression. The gene is the transcriptional control of the nuclear
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
receptor
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
PPAR/RXR heterodimer (Peroxisome proliferator-activated receptor
Peroxisome proliferator-activated receptor
In the field of molecular biology, the peroxisome proliferator-activated receptors are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes...
– Retinoid X receptor
Retinoid X receptor
The retinoid X receptor is a type of nuclear receptor that is activated by 9-cis retinoic acid. There are three retinoic X receptors : RXR-alpha, RXR-beta, and RXR-gamma, encoded by the , , genes, respectively....
) and gene expression can be up regulated using synthetic and natural ligands for PPAR and RXR, including the thiazolidinedione
Thiazolidinedione
The thiazolidinediones , also known as glitazones, are a class of medications used in the treatment of diabetes mellitus type 2. They were introduced in the late 1990s.- Mechanism of action :...
class of anti-diabetic drugs
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
and the vitamin A
Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
metabolite 9-cis-retinoic acid
Retinoic acid
Retinoic acid is a metabolite of vitamin A that mediates the functions of vitamin A required for growth and development. Retinoic acid is required in chordate animals which includes all higher animals from fishes to humans...
respectively.
Tissue distribution
CD36 is found on plateletPlatelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
s, erythrocytes, monocyte
Monocyte
Monocytes are a type of white blood cell and are part of the innate immune system of vertebrates including all mammals , birds, reptiles, and fish. Monocytes play multiple roles in immune function...
s, differentiated adipocyte
Adipocyte
However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...
s, mammary epithelial cells, spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
cells and some skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
microdermal endothelial cells.
Function
The protein itself belongs to the class B scavenger receptorScavenger receptor
Scavenger receptors are a group of receptors that recognize modified low-density lipoprotein by oxidation or acetylation. This naming is based on a function of cleaning : Scavenger receptors widely recognize and uptake macromolecules having a negative charge as well as modified LDL.-Function:It is...
family which includes receptor for selective cholesteryl ester uptake, scavenger receptor class B type I
SCARB1
Scavenger receptor class B member 1 also known as SR-BI is a protein that in humans is encoded by the SCARB1 gene. SR-BI functions as a receptor for high-density lipoprotein....
(SR-BI), and lysosomal integral membrane protein II
SCARB2
Lysosome membrane protein 2 is a protein that in humans is encoded by the SCARB2 gene.- Clinical significance :SCARB2 is a receptor for two viruses that cause hand, foot, and mouth disease in children, Enterovirus 71 and Coxsackievirus A16....
(LIMP-II). CD36 interacts with a number of ligands, including collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
types I and IV, thrombospondin
Thrombospondin
Thrombospondins are secreted proteins with antiangiogenic abilities. TSP was discovered by Nancy L. Baenziger.-Types:The thrombospondins are a family of multifunctional proteins...
, erythrocytes parasitized with Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
, platelet-agglutinating protein p37, oxidized low density lipoprotein
Low density lipoprotein
Low-density lipoprotein is one of the five major groups of lipoproteins, which in order of size, largest to smallest, are chylomicrons, VLDL, IDL, LDL, and HDL, that enable transport of cholesterol within the water-based bloodstream...
and long-chain fatty acids. On macrophages CD36 forms part of a non opsonic receptor (the scavenger receptor CD36/alphaV beta3 complex) and is involved in phagocytosis. CD36 has also been implicated in hemostasis
Hemostasis
Hemostasis or haemostasis is a process which causes bleeding to stop, meaning to keep blood within a damaged blood vessel . Most of the time this includes blood changing from a liquid to a solid state. Intact blood vessels are central to moderating blood's tendency to clot...
, thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
, malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
, inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
, lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
and atherogenesis.
On binding a ligand the protein and ligand are internalized. This internalization is independent of macropinocytosis and occurs by an actin dependent mechanism requiring the activation Src-family kinases, JNK and Rho-family GTPases. Unlike macropinocytosis this process is not affected by inhibitors of phosphatidylinositol 3-kinase or Na+/H+ exchange.
CD36 ligands have also been shown to promote sterile inflammation through assembly of a Toll-like receptor
Toll-like receptor
Toll-like receptors are a class of proteins that play a key role in the innate immune system. They are single, membrane-spanning, non-catalytic receptors that recognize structurally conserved molecules derived from microbes...
4 and 6 heterodimer.
Recently, CD36 was linked to store-operated calcium flux, phospholipase A2 activation, and production of prostaglandin E2
Malaria
Infections with the human malaria parasite Plasmodium falciparumPlasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
are characterized by sequestration of erythrocytes infected with mature forms of the parasite and CD36 has been shown to be a major sequestration receptor on microvascular endothelial cells. Parasitised erythrocytes adhere to endothelium at the trophozoite/schizonts stage simultaneous with the appearance of the var gene product (erythrocyte membrane protein 1) on the erythrocyte surface. The appearance of erythrocyte membrane protein 1 (PfEMP1) on the erythrocyte surface is a temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
dependent phenomenon which is due to increased protein trafficking to the erythrocyte surface at the raised temperature. PfEMP1 can bind other endothelial receptors - thrombospondin
Thrombospondin
Thrombospondins are secreted proteins with antiangiogenic abilities. TSP was discovered by Nancy L. Baenziger.-Types:The thrombospondins are a family of multifunctional proteins...
(TSP) and intercellular adhesion molecule 1 (ICAM-1
ICAM-1
ICAM-1 also known as CD54 is a protein that in humans is encoded by the ICAM1 gene. This gene encodes a cell surface glycoprotein which is typically expressed on endothelial cells and cells of the immune system...
) – in addition to CD36 - and genes other than PfEMP1 also bind to CD36: cytoadherence linked protein (clag) and sequestrin. The PfEMP1 binding site on CD36 is known to be located on exon 5.
CD36 on the surface of the platelets has been shown to be involved in adherence but direct adherence to the endothelium by the infected erythrocytes also occurs. Autoaggregation of infected erythrocytes by platelets has been shown to correlate with severe malaria and cerebral malaria in particular and antiplatelet antibodies may offer some protection.
Several lines of evidence suggest that mutations in CD36 are protective against malaria: mutations in the promoters and within introns and in exon 5 reduce the risk of severe malaria. Gene diversity studies suggest there has been positive selection on this gene presumably due to malarial selection pressure. Dissenting reports are also known
suggesting that CD36 is not the sole determinant of severe malaria. In addition a role for CD36 has been found in the clearance of gametocyte
Gametocyte
A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called spermatocytes, and female gametocytes are called oocytes....
s (stages I and II).
CD36 has been shown to have a role in the innate immune response to malaria in mouse models. Compared with wild type mice CD36 (-/-) mice the cytokine induction response and parasite clearance were impaired. Earlier peak parasitemias, higher parasite densities and higher mortality were noted. It is thought that CD36 is involved in the Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
glycophosphatidylinositol
Glycophosphatidylinositol
Glycosylphosphatidylinositol is a glycolipid that can be attached to the C-terminus of a protein during posttranslational modification...
(PfGPI) induced MAPK activation and proinflammatory cytokine secretion. When macrophages were exposed to PfGPI the proteins ERK1/2, JNK, p38, and c-Jun became phosphorylated. All these proteins are involved as secondary messengers in the immune response. These responses were blunted in the CD36 (-/-) mice. Also in the CD36 (-/-) macrophages secreted significantly less TNF-alpha on exposure to PfGPI. Work is ongoing to determine how these exactly how these responses provide protection against malaria.
CD36 deficiency and alloimmune thrombocytopenia
CD36 is also known as glycoprotein IV (gpIV) or glycoprotein IIIb (gpIIIb) in platelets and gives rise to the NakaNaka
-Places in Japan:* Naka, Hyōgo, a former town in Hyōgo Prefecture* Naka, Ibaraki, a city in Ibaraki Prefecture* Naka, Tokushima, a town in Tokushima Prefecture* Naka District, Ibaraki, a district in Ibaraki Prefecture...
antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
. The Naka null phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
is found in 0.3% of Caucasians and appears to be asymptomatic. The null phenotype is more common in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n (2.5%), Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese, and other Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
n populations (5-11%).
Mutations in the human CD36 gene were first identified in a patient who, despite multiple platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
transfusions, continued to exhibit low platelet levels. This condition is known as refractoriness to platelet transfusion. Subsequent studies have shown that CD36 found on the surface of platelets. This antigen is recognized by the monoclonal antibodies
Monoclonal antibodies
Monoclonal antibodies are monospecific antibodies that are the same because they are made by identical immune cells that are all clones of a unique parent cell....
(MAbs) OKM5 and OKM8. It is bound by the Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
protein sequestrin.
Depending on the nature of the mutation in codon 90 CD36 may be absent either on both platelets and monocytes (type 1) or platelets alone (type 2). Type 2 has been divided in to two subtypes - a and b. Deficiency restricted to the platelets alone is known as type 2a; if CD36 is also absent from the erythoblasts the phenotype is classified as type 2b. The molecular basis is known for some cases: T1264G in both Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
ns and Gambians; C478T (50%), 539 deletion of AC and 1159 insertion of an A, 1438-1449 deletion and a combined 839-841 deletion GAG and insertion of AAAAC in Japanese.
In a study of 827 apparently healthy Japanese volunteers, type I and II deficiencies were found in 8 (1.0%) and 48 (5.8%) respectively. In 1127 healthy French blood donors (almost all of whom were white Europeans) no CD36 deficiency was found. In a second group only 1 of 301 white test subjects was found to be CD36 deficient. 16 of the 206 sub-Saharan black Africans and 1 of 148 black Caribbeans were found to be CD36 -ve. Three of 13 CD36 -ve persons examined had anti CD36 antibodies. In a group of 250 black American blood donors 6 (2.4%) were found to be Naka antigen negative.
CD36 deficiency may be a cause of post transfusion purpura
Purpura
Purpura is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin...
.
Fatty acid uptake
An association with myocardial fatty acid uptake in humans has been noted. The data suggest a link between hypertrophic cardiomyopathyHypertrophic cardiomyopathy
Hypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...
and CD36 but this needs to be confirmed.
Related proteins
Other human scavenger receptorScavenger receptor
Scavenger receptors are a group of receptors that recognize modified low-density lipoprotein by oxidation or acetylation. This naming is based on a function of cleaning : Scavenger receptors widely recognize and uptake macromolecules having a negative charge as well as modified LDL.-Function:It is...
s related to CD36 are SCARB1
SCARB1
Scavenger receptor class B member 1 also known as SR-BI is a protein that in humans is encoded by the SCARB1 gene. SR-BI functions as a receptor for high-density lipoprotein....
and SCARB2
SCARB2
Lysosome membrane protein 2 is a protein that in humans is encoded by the SCARB2 gene.- Clinical significance :SCARB2 is a receptor for two viruses that cause hand, foot, and mouth disease in children, Enterovirus 71 and Coxsackievirus A16....
proteins.