Heat shock protein 70 moderately enhances peptide binding and transport bythe transporter associated with antigen processing

Hsp70 molecules are capable of binding antigenic peptides and eliciting CTL responses to the bound peptide. However, the precise mechanism for the ind uction of CTL has not been determined. One possibility is that hsp molecule s can directly shuttle peptides in the MHC class I antigen processing and p resentation pathway, as previously postulated. Here, we have addressed this issue by testing the effect of purified hsp70 molecules on peptide binding and transport by the transporter associated with antigen processing (TAP). Our results indicate that purified hsp70 molecules moderately enhance TAP function. In addition, we detect a physical association between hsp70 molec ules and TAP, as well as the homologous drug transporter P-glycoprotein. We conclude that while hsp70 molecules may not be directly involved in the de livery of peptide to TAP, they may play an important role in TAP transport by binding to TAP and promoting its function. (C) 2001 Elsevier Science B.V . All rights reserved.