CD81, also named as TAPA-1, is a member of the tetraspanin superfamily of cell surface proteins. Tetraspanins are embedded in the plasma membrane by four transmembrane domains that flank short amino and carboxyl cytoplasmic termini and a small and a large extracellular loop. CD81 is composed of a stalk of two longer α helices and a novel mushroom-like head structure folded with the help of two disulfide bridges. CD81 plays an important role in the regulation of lymphoma cell growth and interacts with a 16-kDa Leu-13 protein to form a complex possibly involved in signal transduction. CD81 may act as the viral receptor for HCV.
|Basic Information of CD81|
|Organism||Homo sapiens (Human)|
CD81 is a broadly expressed protein and is associated with a wide variety of different biological responses, including cell adhesion, morphology, motility, metastasis, proliferation, differentiation, cell activation, and signal transduction. It does so by interacting with a variety of signaling molecules. CD81 is a ligand for HCV in hepatocytes and in T, B, and dendritic cells (DCs), and CD81 and CD9 can modulate HIV-1 membrane fusion and viral clustering at the viral synapse. CD81 is also required for hepatocyte infection by Plasmodium. CD81 plays important roles in adaptive immunity. Researches have confirmed CD81 forms a B cell co-receptor complex with CD19, CD21, Iga, and Igb, and enhances B cell signaling during the process of B cell activation. CD81 could promote IL-4 secretion and antibody production, and also control the organization of the immune synapse (IS) and T cell activation. In addition, the CD19/CD21/CD81 molecular complex bridges the adaptive and innate immune systems.
Fig.1 Cartoon of Claudin-1 and CD81 illustrating their basic topologies. (Bonander, 2011)
This article shows CD81 expressed on T cells as a facilitator of cognate B–T cell interactions, which, in turn, augments intracellular interactions leading to Th2 polarization.
This article suggests that CD81/TfR2 complex regulates hepcidin expression differently from the predicted BMP/SMAD and ERK1/2 signaling pathways.
This article suggests that CD81 plays a regulatory role during systemic Listeria infection by controlling different aspects of immune cell invasion through the modulation of downstream signaling pathways and the regulation of the presentation activity of DCs.
This article reveals that CD81 enhances the effects of the DNA vaccine and could be used as a potential genetic adjuvant for other DNA vaccines.
This article suggests that no sequence variation is found in any of the patients studied by either method, including gene sections encoding the residues most important for CD81-HCV E2 binding.
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