CD81 antigen (CD81) (CD81)

CD81 antigen (CD81), also known as TAPA-1 or Tetraspanin-28, is a member of the tetraspanin superfamily characterized by four transmembrane domains [5, 12]. It plays a fundamental role in organizing "tetraspanin-enriched microdomains" (TERMs), which act as platforms for receptor clustering, signal transduction, and protein trafficking [11, 12]. CD81 is a critical co-receptor for the hepatitis C virus (HCV) and is involved in the entry of other pathogens like Plasmodium and HIV-1 [1, 5, 10]. In the immune system, it associates with CD19 and CD21 to form the B-cell co-receptor complex, which lowers the threshold for B-cell activation [4, 12, 15]. Beyond its physiological roles in cell adhesion and motility, CD81 is frequently overexpressed in various malignancies, including B-cell lymphomas and triple-negative breast cancer, where it promotes tumor progression and metastasis [1, 3, 13]. Therapeutic strategies targeting CD81 include monoclonal antibodies (such as 5A6) and small molecules designed to block viral entry or inhibit cancer cell migration, although none have yet reached clinical approval [1, 6, 15].

Other names

TAPA-1Tetraspanin-28TSPAN2826 kDa cell surface proteinCVID6S5.7

Inhibition of viral entry by blocking the interaction between CD81 and viral envelope proteins; inhibition of cancer cell migration and invasion through cross-linking and recruitment of partner proteins; modulation of B-cell receptor signaling thresholds.