Transporter associated with antigen processing (TAP)

The Transporter associated with antigen processing (TAP) is a critical heterodimeric protein complex, consisting of TAP1 (ABCB2) and TAP2 (ABCB3) subunits, located in the endoplasmic reticulum (ER) membrane (UniProt P21964, P35670). It belongs to the ATP-binding cassette (ABC) transporter family and plays a central role in the MHC class I antigen presentation pathway by pumping proteasome-generated peptides from the cytosol into the ER lumen (Abele & Tampé, 2004). Once inside the ER, these peptides are loaded onto MHC class I molecules for subsequent display on the cell surface to CD8+ cytotoxic T lymphocytes. Deficiencies or downregulation of TAP are frequently observed in various cancers, allowing tumors to evade immune detection by reducing the presentation of neoantigens (NIH Gene ID: 6890). Conversely, many viruses have evolved specific proteins, such as ICP47 from herpes simplex virus and US6 from cytomegalovirus, to inhibit TAP function and escape the host immune response (Wikipedia). While there are currently no FDA-approved small molecule drugs specifically targeting TAP, it remains a significant area of research for immunotherapy, cancer vaccines, and the treatment of autoimmune disorders.

Other names

Antigen peptide transporterTAP1/TAP2 complexABCB2/ABCB3 complexPeptide transporter TAPATP-binding cassette sub-family B member 2/3

Inhibition of ATP-dependent peptide transport into the endoplasmic reticulum, preventing MHC class I assembly and surface expression.