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Human immunodeficiency virus 1 Tat binds to dipeptidyl aminopeptidase IV (CD26): a possible mechanism for Tat's immunosuppressive activity.

Abstract：

:The human immunodeficiency virus 1 (HIV-1) Tat protein suppresses antigen-induced, but not mitogen-induced, activation of human T cells when added to T-cell cultures [Viscidi, R. P., Mayur, K., Lederman, H. M. & Frankel, A. D. (1989) Science 246, 1606-1608]. This activity is potentially pertinent to the development of AIDS because lymphocytes from HIV-infected individuals exhibit a similar antigen-specific dysfunction. Here we report that Tat binds with high affinity to the T-cell activation molecule dipeptidyl aminopeptidase IV (DP IV), also known as CD26. This molecule occurs on the surface of CD4+ cells responsible for the recall antigen response and appears to play an essential role in this response. Tat binds to both the cell surface and soluble forms of DP IV at physiological salt concentrations without inhibiting the protease activity of DP IV against small chromogenic substrates used to assay activity, but Tat markedly inhibits the activity of DP IV at lower salt concentrations. The kinetics of inhibition indicate the affinity of Tat for DP IV varies from 20 pM to 11 nM, and the activity of the Tat-DP IV complex varies from 13% to 100%, as the NaCl concentration varies from 0 to 140 mM. Cytofluorometry experiments demonstrate that Tat competes with anti-Ta1, a monoclonal antibody (mAb) specific for DP IV, for binding to cell surface DP IV, thus indicating that Tat binds DP IV at or near the Ta1 epitope. Moreover, the anti-Ta1 mAb blocks the immunosuppressive activity of Tat. The high affinity of Tat for DP IV, previous evidence implicating DP IV in antigen-specific T-cell activation events, and the ability of anti-Ta1 mAb to block the immunosuppressive effect of Tat make DP IV a plausible receptor for Tat's immunosuppressive activity.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Gutheil WG,Subramanyam M,Flentke GR,Sanford DG,Munoz E,Huber BT,Bachovchin WW

doi

10.1073/pnas.91.14.6594

subject

Has Abstract

pub_date

1994-07-05 00:00:00

pages

6594-8

issue

eissn

0027-8424

issn

1091-6490

journal_volume

pub_type

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Human immunodeficiency virus 1 Tat binds to dipeptidyl aminopeptidase IV (CD26): a possible mechanism for Tat's immunosuppressive activity.