CD81: A Crucial Tetraspanin Protein in Cell Signalling and Disease

Structure and Molecular Characteristics

CD81 is also referred to as TAPA‐1 (Target of Anti-proliferative Antibody 1) and it falls under the tetraspanin superfamily of proteins with a molecular weight of 26 kDa. The protein is made up of four transmembrane domains that create two loops and internal N‐ and C terminal tails. The substantial external loop (LEL) exhibits distinct structural characteristics; it includes conserved cysteine residues that establish disulfide bonds essential, for protein stability and interaction, with other molecules. The tiny extracellular loop (SEL) though so than others mentioned earlier in the text also plays a role, in the proteins function successfully completed tasks of organizing membrane microdomains, by CD81s structure that are commonly known as tetraspanin enriched microdomains (TEM) aiding in cell functions simultaneously.

Expression Pattern and Distribution

CD81 is widely expressed in cell types and tissues which indicates its role, in cellular functions across the body’s systems like immune cells (B cells and T cells) as well as antigen present cells and other cell types such as hepatocytes, neurons, endothelial cells and epithelial tissues. This shows that CD81 is involved in processes due to its widespread presence in different areas of the body. The levels of CD81 expression can change dynamically based on factors such, as cell activation, stress or disease conditions. The proteins existence, on exosomes and other tiny particles outside cells expands its impact beyond cells by aiding communication, between cells.

Role in Immune System Function

CD81 has been identified to play various roles in its regulation functions. of In the B immune cells system, it as forms well a as complex with CD19 and CD21 to create a co-receptor which makes the threshold for B cell activation through the B cell receptor (BCR) higher but when it is set it is lower than it would otherwise be. This interaction is very the important appropriate for functioning of antibody producing cells and humoral immune responses. In T cells CD81 acts on T cell receptor signalling and thus on cell activation, proliferation as well as on cytokine production. The protein also has an impact on the formation of immune synapse that is critical for the interactions between the immune as cells. the Furthermore, control the of product the of migration this of gene the is immune involved cells in via its processes regulation of antigen adhesion presentation molecules as well as chemokines.

Involvement in Disease Processes

CD81 is involved in many diseases where it plays a role. In the field of infectious diseases, it acts as a co-receptor for the hepatitis C virus thus offering a possible target for anti-viral treatment. In cancer biology it has been shown that CD81 can have both oncogenic and tumor suppressor functions based on the cancer type and cellular microenvironment. In metastasis CD81 regulates cell adhesion and signalling pathways that are involved in cell migration and invasion. CD81 has been identified to regulate platelet function and vascular cell behaviour and thus it is involved in the progression of cardiovascular diseases.

Suitable ELISA Kits

• • CD81 ELISA Kit