Editing CD81

'''CD81''' is a [[protein]] that in humans is encoded by the ''CD81'' [[gene]]. It is also known as '''TAPA-1''' (Target of the Antiproliferative Antibody 1) and '''TSPAN28''' (Tetraspanin-28). CD81 is a member of the [[tetraspanin]] family, which are integral membrane proteins involved in several important biological processes.

== Structure ==
CD81 is a cell surface protein that spans the membrane four times, hence the name tetraspanin. It has a small and a large extracellular loop, with the large loop being the primary site for [[antibody]] binding. The protein is 236 [[amino acids]] long and has a molecular weight of approximately 26 kDa.

== Function ==
CD81 plays a crucial role in several cellular processes, including [[cell adhesion]], [[cell motility]], and [[cell proliferation]]. It is also involved in the regulation of [[B cell]] and [[T cell]] activation. CD81 interacts with other proteins, such as [[CD19]], [[CD21]], and [[MHC class II]] molecules, to form the B cell co-receptor complex, which plays a critical role in B cell activation and [[antibody production]].

In addition to its role in immune cell function, CD81 is also a receptor for [[Hepatitis C virus]] (HCV). The virus binds to CD81 on the surface of [[hepatocytes]], facilitating its entry into the cell.

== Clinical significance ==
Given its role in HCV entry, CD81 is a potential target for antiviral therapies. Inhibiting the interaction between HCV and CD81 can prevent the virus from entering hepatocytes, thereby preventing infection.

Furthermore, alterations in CD81 expression have been associated with various diseases, including [[cancer]]. Overexpression of CD81 has been observed in several types of cancer, including [[breast cancer]] and [[melanoma]], and is associated with increased cell motility and invasiveness.

== See also ==
* [[Tetraspanin]]
* [[Hepatitis C virus]]
* [[B cell]]
* [[T cell]]
* [[Cancer]]

== References ==
<references />

[[Category:Proteins]]
[[Category:Genes]]
[[Category:Immunology]]
[[Category:Virology]]
[[Category:Oncology]]

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