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TAP2
TAP2 Full Name
transporter 2, ATP-binding cassette, sub-family B (MDR/TAP)
TAP2 Introduction
TAP2 is the heterodimer chaperone of TAP1 which is responsible for peptide loading onto MHC class I molecules. They are heterodimeric ER membrane peptide transporters that cooperate to translocate proteasome-generated peptide fragments from the cytosol into the ER lumen, using ATP hydrolysis. This step permits efficient assembly and surface expression of MHC I–peptide complexes. As this pathway supports immune surveillance by CD8+ T cells, TAP2 is also viewed as a key mediator of antigen processing, cellular immunity and tumor immunogenicity.
Figure 1. Schematic depiction of the FRET assay for measuring TAP1- TAP2 NBD interactions.(Source: Geng J, et al.; 2013)
Biologically, TAP2 has been shown to be important in selection of peptides, efficiency of transport and stability of MHC class I complexes. Alterations in TAP2 expression or function can affect the range of peptide repertoire that may be altered in thresholds of T-cell recognition and host defense strategies. The transporter's role extends beyond classical antigen presentation, influencing NK-cell interactions through its impact on MHC I surface density. Experimental studies have demonstrated that TAP2 deficiency leads to accumulation of unbound peptides in the cytosol, ER stress responses, and reduced immune activation, while certain polymorphisms modify peptide transport affinity or ATP-binding kinetics, shaping individual immune responsiveness.
Clinically, deficient/dysregulated TAP2 activity has been observed in various immune-related diseases. TAP2 mutations are known to be present in type I bare lymphocyte syndrome (Primary immunodeficiency with an exceptionally low expression of MHC I) and a greater tendency to viral infection. TAP2 expression is also altered in certain cancers. On the other hand, the transporter's expression can be decreased by tumors in order to render themselves more invisible to cytotoxic T-cells. Polymorphisms in TAP2 have been linked to some autoimmune diseases, possibly due to altered antigen presentation. These clinical correlations illustrate the utility of TAP2 both as a mechanistic immunomodulator as well as a potentially critical biomarker in immunologic, oncologic and precision-medicine research.
Alternate Names for TAP2
TAP2; transporter 2, ATP-binding cassette, sub-family B (MDR/TAP); ABCB3; antigen peptide transporter 2; D6S217E; PSF2; RING11; ABC transporter, MHC 2; peptide supply factor 2; peptide transporter PSF2
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