TAPA-1/CD81 Extracellular Domain (human, recombinant; His-tagged)

CD81, also known as target of antiproliferative antibody 1 (TAPA-1), is a member of the tetraspanin protein family with roles in B cell biology and T cell activation and as a virus host factor.^1,2 It is composed of four transmembrane segments, which are packed as two pairs of helices, and an extracellular loop at the outer membrane leaflet that, unlike other tetraspanin proteins, is non-glycosylated and subject to post-translational acylation.^2,3 On the surface of B cells, CD81 associates with CD19 and CD21 to facilitate adhesion and reduce the threshold for B cell receptor activation, as well as with MHC class II molecules as a component of the B cell surface receptor complex.^3,4,5 On T cells, CD81 interacts with CD4 and CD8 and functions as a co-stimulator of naïve T cell activation in conjunction with CD3 and CD28.^1,6 CD81 also acts as a virus host factor, and neutralization of CD81 with anti-CD81 antibodies reduces HIV-1 replication and inhibits influenza A virus uncoating and viral budding, as well as inhibits coronavirus (CoV) and hepatitis C virus (HCV) cell entry.⁷ CD81 levels are increased in several lymphoma cell lines, and antibody-driven neutralization of CD81 induces complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and cytotoxicity in these cells.⁵ Cayman’s TAPA-1/CD81 Extracellular Domain (human, recombinant; His-tagged) protein consists of 108 amino acids and has a calculated molecular weight of 12.1 kDa.

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1. Sagi, Y., Landrigan, A., Levy, R., et al. Complementary costimulation of human T-cell subpopulations by cluster of differentiation 28 (CD28) and CD81. Proc. Natl. Acad. Sci. USA 109(5), 1613-1618 (2012).

2. Zimmerman, B., Kelly, B., McMillan, B.J., et al. Crystal structure of a full-length human tetraspanin reveals a cholesterol-binding pocket. Cell 167(4), 1041-1051 (2016).

3. Levy, S., Todd, S.C., and Maecker, H.T. CD81 (TAPA-1): A molecule involved in signal transduction and cell adhesion in the immune system. Annu. Rev. Immunol. 16, 89-109 (1998).

4. Szöllósi, J., Horejsí, V., Bene, L., et al. Supramolecular complexes of MHC class I, MHC class II, CD20, and tetraspan molecules (CD53, CD81, and CD82) at the surface of a B cell line JY. J. Immunol. 157(7), 2939-2946 (1996).

5. Küppers, R. CD81 as target for B cell lymphomas. J. Exp. Med. 216(7), 1469-1470 (2019).

6. Schultz, L.M., Czerwinski, D.K., Levy, R., et al. CD81 costimulation skews CAR transduction toward naive T cells. Proc. Natl. Acad. Sci. USA 119(5), e1910844119 (2022).

7. New, C., Lee, Z.-Y., Tan, K.S., et al. Tetraspanins: Host factors in viral infections. Int. J. Mol. Sci. 22(21), 11609 (2021).