CD81
Encyclopedia
CD81 molecule, also known as CD81 (Cluster of Differentiation 81), is a protein
which in humans is encoded by the CD81 gene
. It is also known as 26 kDa cell surface protein, Target of the antiproliferative antibody 1 (TAPA-1) and Tetraspanin-28 (Tspan-28).
s (predicted molecular weight 25.809 kDa
).
The protein does not appear to be post translationally modified and has four transmembrane domains. Both the N-terminus and C-terminus lie on the intracellular side of the membrane.
The gene is expressed in hemopoietic, endothelial and epithelial cells. It is absent from erythrocytes, platelet
s and neutrophils.
family. Most of these members are cell-surface proteins that are characterized by the presence of four hydrophobic domain
s. The proteins mediate signal transduction
events that play a role in the regulation of cell development, activation, growth and motility. This encoded protein is a cell surface glycoprotein
that is known to complex with integrins. This protein appears to promote muscle cell fusion and support myotube maintenance. Also it may be involved in signal transduction. This gene is localized in the tumor-suppressor gene region and thus it is a candidate gene for malignancies.
The tetraspanin family includes CD9
, CD37
, CD53
, CD63
, CD81 (this protein), CD82 and CD151
.
CD81 interacts directly with immunoglobulin superfamily member 8 (IGSF8
, CD316) and CD36
. It forms a signal transduction complex with CD19
, CD21 and Leu-13 (CD225
) on the surface of the B cell
. On T cell
s CD81 associates with CD4
and CD8
and provides a costimulatory signal with CD3
.
attachment and/or cell entry by interacting with virus' E1/E2 glycoproteins heterodimer.
It also appears to play a role in liver
invasion by Plasmodium
species.
The HIV
Gag proteins bind this protein on the cell surface.
with TSPAN4
, CD19
, CD9
, PTGFRN
, CD117
and CD29
.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
which in humans is encoded by the CD81 gene
Gene
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...
. It is also known as 26 kDa cell surface protein, Target of the antiproliferative antibody 1 (TAPA-1) and Tetraspanin-28 (Tspan-28).
Molecular biology
The gene is located Watson (plus) strand of the short arm of chromosome 11 (11p15.5). It is 20,103 bases in length and encodes a protein of 236 amino acidAmino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s (predicted molecular weight 25.809 kDa
DA
DA, da, or dA may refer to:* Da , a Tony-winning play by Hugh Leonard* Da , a movie adaptation of the play by Hugh Leonard* Adi Da, a spiritual leader once known as Da Free John, and Da Love-Ananda...
).
The protein does not appear to be post translationally modified and has four transmembrane domains. Both the N-terminus and C-terminus lie on the intracellular side of the membrane.
The gene is expressed in hemopoietic, endothelial and epithelial cells. It is absent from erythrocytes, 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...
s and neutrophils.
Biochemistry
The protein encoded by this gene is a member of the transmembrane 4 superfamily, also known as the tetraspaninTetraspanin
Tetraspanins are a family of membrane proteins found in all multicellular eukaryotes.Tetraspanins, also called tetraspans or the transmembrane 4 superfamily , have four transmembrane domains, intracellular N- and C-termini and two extracellular domains, one short and one longer, typically 100...
family. Most of these members are cell-surface proteins that are characterized by the presence of four hydrophobic domain
Protein domain
A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...
s. The proteins mediate signal transduction
Signal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
events that play a role in the regulation of cell development, activation, growth and motility. This encoded protein is a cell surface glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
that is known to complex with integrins. This protein appears to promote muscle cell fusion and support myotube maintenance. Also it may be involved in signal transduction. This gene is localized in the tumor-suppressor gene region and thus it is a candidate gene for malignancies.
The tetraspanin family includes CD9
CD9
CD9 antigen is a protein that in humans is encoded by the CD9 gene.-Interactions:CD9 has been shown to interact with TSPAN4, PTGFRN, CD81, CD117, CD46, CD29 and CD49c.-Further reading:...
, CD37
CD37
Leukocyte antigen CD37 is a protein that in humans is encoded by the CD37 gene.-External links:...
, CD53
CD53
Leukocyte surface antigen CD53 is a protein that in humans is encoded by the CD53 gene.-External links:...
, CD63
CD63
CD63 antigen is a protein that in humans is encoded by the CD63 gene.CD63 is a good marker for flow cytometric quantification of in vitro activated basophils for diagnosis of IgE-mediated allergy. The test is commonly designated as basophil activation test -Interactions:CD63 has been shown to...
, CD81 (this protein), CD82 and CD151
CD151
CD151 molecule , also known as CD151 , is a human gene.-Further reading:...
.
CD81 interacts directly with immunoglobulin superfamily member 8 (IGSF8
IGSF8
Immunoglobulin superfamily member 8 is a protein that in humans is encoded by the IGSF8 gene.IGSF8 has also been designated as CD316 ....
, CD316) and CD36
CD36
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 and glycoprotein IIIb . CD36 is a member of the class B scavenger receptor family of cell surface proteins...
. It forms a signal transduction complex with CD19
CD19
B-lymphocyte antigen CD19 also known as CD19 , is a protein that in humans is encoded by the CD19 gene.- Function :...
, CD21 and Leu-13 (CD225
IFITM1
Interferon-induced transmembrane protein 1 is a protein that in humans is encoded by the IFITM1 gene. IFITM1 has also recently been designated CD225 ....
) on the surface of the B cell
B cell
B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...
. On T cell
T cell
T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...
s CD81 associates with CD4
CD4
CD4 is a glycoprotein expressed on the surface of T helper cells, monocytes, macrophages, and dendritic cells. It was discovered in the late 1970s and was originally known as leu-3 and T4 before being named CD4 in 1984...
and CD8
CD8
CD8 is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor . Like the TCR, CD8 binds to a major histocompatibility complex molecule, but is specific for the class I MHC protein. There are two isoforms of the protein, alpha and beta, each encoded by a different gene...
and provides a costimulatory signal with CD3
CD3
CD3 or CD-3 may be:* CD3 , an antigen, cluster of differentiation protein , part of the T cell receptor complex on a mature T lymphocyte* Ford CD3 platform* MediaMax CD-3, copy protection scheme* MiniCD, a 3-inch CD...
.
Clinical
This protein plays a critical role in Hepatitis CHepatitis C
Hepatitis C is an infectious disease primarily affecting the liver, caused by the hepatitis C virus . The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years...
attachment and/or cell entry by interacting with virus' E1/E2 glycoproteins heterodimer.
It also appears to play a role in liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
invasion by Plasmodium
Plasmodium
Plasmodium is a genus of parasitic protists. Infection by these organisms is known as malaria. The genus Plasmodium was described in 1885 by Ettore Marchiafava and Angelo Celli. Currently over 200 species of this genus are recognized and new species continue to be described.Of the over 200 known...
species.
The HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
Gag proteins bind this protein on the cell surface.
Interactions
CD81 has been shown to interactProtein-protein interaction
Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...
with TSPAN4
TSPAN4
Tetraspanin-4 is a protein that in humans is encoded by the TSPAN4 gene.-Interactions:TSPAN4 has been shown to interact with CD9, ITGA6, CD29, CD49c and CD81.-Further reading:...
, CD19
CD19
B-lymphocyte antigen CD19 also known as CD19 , is a protein that in humans is encoded by the CD19 gene.- Function :...
, CD9
CD9
CD9 antigen is a protein that in humans is encoded by the CD9 gene.-Interactions:CD9 has been shown to interact with TSPAN4, PTGFRN, CD81, CD117, CD46, CD29 and CD49c.-Further reading:...
, PTGFRN
PTGFRN
Prostaglandin F2 receptor negative regulator is a protein that in humans is encoded by the PTGFRN gene. PTGFRN has also been designated as CD315 .-Interactions:PTGFRN has been shown to interact with CD9 and CD81....
, CD117
CD117
Mast/stem cell growth factor receptor also known as proto-oncogene c-Kit or tyrosine-protein kinase Kit or CD117 is a protein that in humans is encoded by the KIT gene...
and CD29
CD29
Integrin beta-1 is a protein that in humans is encoded by the ITGB1 gene. CD29 is an integrin unit associated with very late antigen receptors. It is known to conjoin with alpha-3 subunit to create α3β1 complex that reacts to such molecules as netrin-1 and reelin.Integrins are heterodimeric...
.