Crystal Structures of HIV-1 Tat-derived Nonapeptides Tat-(1–9) and Trp2-Tat-(1–9) Bound to the Active Site of Dipeptidyl-peptidase IV (CD26)

Wilhelm Andreas Weihofen,Wolfram Saenger,Jianguo Liu,Werner Reutter,Hua Fan

doi:10.1074/jbc.m413400200

Wilhelm Andreas Weihofen, Wolfram Saenger + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m413400200

Copy DOI

Abstract

CD26 or dipeptidyl-peptidase IV (DPPIV) is engaged in immune functions by co-stimulatory effects on activation and proliferation of T lymphocytes, binding to adenosine deaminase, and regulation of various chemokines and cytokines. DPPIV peptidase activity is inhibited by both Tat protein from human immunodeficiency virus (HIV)-1 and its N-terminal nonapeptide Tat-(1-9) with amino acid sequence MDPVDPNIE, suggesting that DPPIV mediates immunosuppressive effects of Tat protein. The 2.0- and 3.15-A resolution crystal structures of the binary complex between human DPPIV and nonapeptide Tat-(1-9) and the ternary complex between the variant MWPVDPNIE, called Trp(2)-Tat-(1-9), and DPPIV bound to adenosine deaminase show that Tat-(1-9) and Trp(2)-Tat-(1-9) are located in the active site of DPPIV. The interaction pattern of DPPIV with Trp(2)-Tat-(1-9) is tighter than that with Tat-(1-9), in agreement with inhibition constants (K(i)) of 2 x 10(-6) and 250 x 10(-6) m, respectively. Both peptides cannot be cleaved by DPPIV because the binding pockets of the N-terminal 2 residues are interchanged compared with natural substrates: the N-terminal methionine occupies the hydrophobic S1 pocket of DPPIV that normally accounts for substrate specificity by binding the penultimate residue. Because the N-terminal sequence of the thromboxane A2 receptor resembles the Trp(2)-Tat-(1-9) peptide, a possible interaction with DPPIV is postulated.

Highlights

CD26 or dipeptidyl-peptidase IV (DPPIV) is engaged in immune functions by co-stimulatory effects on activation and proliferation of T lymphocytes, binding to adenosine deaminase, and regulation of various chemokines and cytokines
DPPIV peptidase activity is inhibited by both Tat protein from human immunodeficiency virus (HIV)-1 and its N-terminal nonapeptide Tat-(1–9) with amino acid sequence MDPVDPNIE, suggesting that DPPIV mediates immunosuppressive effects of Tat protein
Full-length Tat inhibits DPPIV with high affinity (Ki ϭ 0.02–11 nM) (16), whereas the N-terminal nonapeptide Tat-(1–9) with sequence MDPVDPNIE acts as weak inhibitor of DPPIV activity at a Ki of 250 ␮M (17), and full-length Tat protein that was N-terminally modified with rhodamine lacks any inhibitory potential

Summary

Introduction

CD26 or dipeptidyl-peptidase IV (DPPIV) is engaged in immune functions by co-stimulatory effects on activation and proliferation of T lymphocytes, binding to adenosine deaminase, and regulation of various chemokines and cytokines. CD26 or dipeptidyl-peptidase IV (DPPIV)[1] (EC 3.4.14.5) is a ubiquitous, multifunctional integral type II membrane glycoprotein located on the surface of a variety of epithelial, endothelial, and lymphoid cells. As an exopeptidase, it cleaves Nterminal dipeptides from polypeptides with proline or alanine in the penultimate position, thereby regulating the activity of a. Variety of biologically important peptides (2, 3) Some of these peptides are closely related to immune function, such as GLP-1 (glucagon-like peptide), GIP (glucose-dependent insulinotropic polypeptide) (4), RANTES (regulated on activation, normal T cell expressed and secreted) (5), MDC (monocyte-derived chemokine) (6), SDF-1␣ and SDF-1␤ (stromally derived factors) (7), eotaxin (8), and LD78␤ (9). Because monocytes interact strongly with T cells carrying DPPIV, it was suggested that, similar to Tat protein, an interaction between the N terminus of thromboxane A2 receptor and DPPIV might modulate T-cell activation by inhibiting DPPIV proteolytic activity (19)

Methods

Results

Conclusion