The costimulatory activity of the CD26 antigen requires dipeptidyl peptidase IV enzymatic activity.

Abstract

T cells have been shown to express CD26, a known ectoenzyme with dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5) activity in its extracellular domain. CD26 can also deliver a second costimulatory signal and contribute to T-cell activation. In an earlier study, we established CD26-transfected Jurkat T-cell lines and demonstrated that monoclonal antibody-mediated crosslinking of CD26 and CD3 induced interleukin 2 (IL-2) production. To determine the contribution of DPPIV enzymatic activity to the costimulatory activity of CD26, human CD26 cDNA was mutated so that active-site serine was replaced by alanine. The mutant CD26 antigen lacked DPPIV enzyme activity but still retained reactivity with three anti-CD26 monoclonal antibodies directed against distinct epitopes of CD26. After stimulation with a combination of anti-CD26 and anti-CD3 antibodies, wild-type CD26 (DPPIV+)-transfected Jurkat cells produced substantially more IL-2 than did mutant CD26 (DPPIV-) or CD26-control transfectants. Nevertheless, the mutant CD26-transfected cells still produced significantly more IL-2 than did CD26-control transfectants. These results suggest that DPPIV activity plays an important but not absolute role in the costimulatory activity of CD26 in this system. We also found that wild-type CD26 (DPPIV+) transfectants produced more IL-2 than mutant CD26 (DPPIVj)-transfected cells or CD26-control transfectants when triggered by stimuli not involving CD26, such as anti-CD3 and phorbol ester. These results suggest that the DPPIV activity of CD26 functions to augment the cellular responses of CD26-transfected Jurkat cells to external stimuli mediated by CD26 and/or the CD3/T-cell receptor complex, thus enhancing IL-2 production.

Effect of CD26/dipeptidyl peptidase IV on Jurkat sensitivity to G2/M arrest induced by topoisomerase II inhibitors

“…CD26 is also involved in T-cell activation, owing to its association with CD45, mannose 6-phosphate/insulin-like growth factor II receptor and adenosine deaminase (ADA) (Morimoto et al, 1989;Dang et al, 1990aDang et al, -d, 1991Torimoto et al, 1991;Kameoka et al, 1993;Morrison et al, 1993;Ikushima et al, 2000). Additionally, its DPPIV enzyme activity has a key role in various aspects of T-cell activation, as demonstrated by studies using DPPIV inhibitors, soluble CD26/DPPIV molecules or CD26 genetic mutants (Flentke et al, 1991;Tanaka et al, 1993Tanaka et al, , 1994Steinbrecher et al, 2001). Besides its involvement in normal T-cell function, CD26 may also have a role in the development of certain tumors (Tanaka et al, 1995;Stecca et al, 1997;Bauvois et al, 1999;Dang and Morimoto, 2002).…”

Enhancement of antigen-induced T-cell proliferation by soluble CD26/dipeptidyl peptidase IV.

“…Our recent studies have shown that the DPPIV enzyme activity of CD26 functions to augment cellular responses of CD26-transfected Jurkat cells to external stimuli (13). These studies raise questions as to how CD26 functions in a physiological situation.…”

“…1, line 2). The small Xba I-Dra III DNA fragment of the mutant CD26 cDNA containing the deletion was substituted for the corresponding DNA fragment of the wild-type CD26 cDNA in the expression vector RcSRa to yield RcSRa-26A3-9 (13). A mixture of RcSRa-26.A&3-9 and pMT-2 (14) providing the dihydrofolate reductase (DHFR) gene was used to transfect a DHFR-deficient CHO cell line, DXB-11, by electroporation (15).…”

“…Transfectants grown in nucleoside-deficient selection medium were screened for sCD26 production by measuring DPPIV enzyme activity (13) and appearance of a 110-kDa band in the supernatant of metabolically labeled cells (16 ration, resuspended in phosphate-buffered saline (PBS), loaded on a concanavalin A-Sepharose (Pharmacia) column, and eluted with 0.2 M methyl a-D-mannopyranoside (Sigma). The sCD26-containing fractions identified by DPPIV enzyme assay were pooled and precleared by passage through a column of bovine serum albumin-conjugated Affl-Gel 10 (Bio-Rad) and then applied to an anti-CD26 mAb (1F7)-conjugated Affi-Gel-10 column.…”

CD26-Mediated Induction of EGR2 and IL-10 as Potential Regulatory Mechanism for CD26 Costimulatory Pathway

“…Our present data strongly suggest that persistent NFAT-AP-1 cooperation is responsible for CD26-mediated T cell activation, and sustained activation of NFAT and ERK1/2 is possibly due to the aggregation of signaling molecules in lipid rafts following CD26-mediated costimulation. Furthermore, we have previously shown that DPPIV enzyme activity is partially involved in the costimulatory activity of CD26 through studies using wild-type CD26 (DPPIV + ) or mutant CD26 (DPPIV 2 )-transfected Jurkat T cell lines (55). Other groups reported that the synthetic competitive DPPIV inhibitor Lys[Z(NO 2 )] significantly suppressed the proliferation and production of IL-2, IL-10, and IFN-g in PWM-stimulated human T cells (56).…”