Binding of the T cell activation monoclonal antibody Ta1 to dipeptidyl peptidase IV

Lower activity of serum peptidases in abstinent alcohol-dependent patients

This study examines i) the activity of serum prolyl endopeptidase (PEP) and dipeptidlyl peptidase IV (DPP IV) in detoxified alcohol-dependent patients without liver disease versus normal controls, and ii) the relationships between serum DPP IV and PEP activity and the production of cytokines or cytokine receptors, such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), interferon-y (IFN-y), IL-1 receptor antagonist (IL-1RA), and IL-10, and granulocyte-macrophage colony stimulatory factor (GM-CSF). Alcohol-dependent patients had significantly lower serum PEP and DPP IV activity than normal controls. We found that 58.3% and 50.0% of the alcohol-dependent patients, respectively, had PEP and DPP IV activities, which were lower than the mean control values minus 2 SD. There were significant inverse correlations between lowered serum DPP IV and PEP activity and the increased production of IL-6, INF-gamma, IL-IRA, IL-10, and GM-CSF. These results show that lower serum DPP IV and PEP activity may be related to the pathophysiology of alcohol dependence.

Inhibition of dipeptidyl peptidase IV by fluoroolefin-containing N-peptidyl-O-hydroxylamine peptidomimetics

Dipeptidyl peptidase IV (EC 3.4.14.5; DPP IV), also known as the leukocyte differentiation antigen CD26 when found as an extracellular membrane-bound proline specific serine protease, cleaves a dipeptide from the N terminus of a polypeptide chain containing a proline residue in the penultimate position. Here we report that known (Z)-Ala-psi[CF=C]-Pro dipeptide isosteres 1 and 2, which contain O-acylhydroxylamines, were isolated as diastereomeric pairs u-1, l-1, and l-2. The effect of each diastereomeric pair as an inhibitor of human placental dipeptidyl peptidase DPP IV has been examined. The inhibition of DPP IV by these compounds is rapid and efficient. The diastereomeric pair u-1 exhibits very potent inhibitory activity with a Ki of 188 nM. Fluoroolefin containing N-peptidyl-O-hydroxylamine peptidomimetics, by virtue of their inhibitory potency and stability, are superior to N-peptidyl-O-hydroxylamine inhibitors derived from an Ala-Pro dipeptide.

CD26/dipeptidyl peptidase IV does not work as an adenosine deaminase-binding protein in rat cells

In this paper, we describe further characterization of the membrane-associated molecule CD26/dipeptidyl peptidase IV (DPP IV), which is said to be adenosine deaminase-binding protein (ADA-bp) in humans, to clarify its association with ADA in rat immune cells. For this purpose, we used three types of rats: DPP IV+ rats; DPP IV- rats, which lack enzyme activity and immunological reactivity of DPP IV; and ADA- rats, which have reduced ADA activity due to continuous peritoneal injection of 2'-DCF, a potent inhibitor of ADA. ADA existed in the cells of DPP IV+ and DPP IV- rats, but it did not exist on the cell surface in either rat. ADA- rats showed a decrease in ADA activity and in the number of immune cells, but no effect on DPP IV was observed. These data suggest that in rats, in contrast to humans, DPP IV does not exist as ADA-bp.

Lower serum dipeptidyl peptidase IV activity in treatment resistant major depression: relationships with immune-inflammatory markers

Previous research in this laboratory has shown that major depression is accompanied by decreased serum activity of dipeptidyl peptidase IV (DPP IV), a serine protease that cleaves N terminal dipeptides from peptides with penultimate proline or alanine. DPP IV is involved in the metabolism of peptides, T cell activation and proliferation, including the production of cytokines, such as interleukin-1 (IL-1) and IL-2. The aim of this study was to examine (i) serum DPP IV activity in major and treatment resistant depression (TRD) in relation to other established immune and inflammatory markers of that illness, and (ii) the effects of antidepressive treatment on DPP IV activity. Serum DPP IV activity was significantly lower in major depression and TRD than in normal controls. In normal and major depressed subjects, there were significant and positive relationships between serum DPP IV activity and total serum protein, serum albumin, zinc, iron and transferrin. In the group of depressed subjects, there were significant and positive relationships between serum DPP IV activity and number of CD4+T cells and CD4+/CD8+ T cell ratio. There were no significant effects of subchronic treatment with antidepressants on serum DPP IV activity. The findings suggest that: (i) lower serum DPP activity may occur in chronic depression, TRD as well as in the acute phase of major depression; (ii) lower serum DPP IV accompanies the 'chronic' acute phase response in depression; and (iii) serum DPP IV activity is tightly coupled to increased number of CD4+ T cells in depressed subjects, but not in normal controls. Our results do not exclude the possible effects of longer-term treatment with antidepressants on serum DPP-IV activity.

Suppression of arthritis by the inhibitors of dipeptidyl peptidase IV

Dipeptidyl peptidase IV (DP IV, CD26) is a serine exoprotease which selectively cleaves the penultimate proline residue of polypeptides. This enzyme is also expressed as a surface marker on activated T cells. In order to assess the relevance of DP IV in immunological disorders, we evaluated the in vivo effects of specific DP IV inhibitors using two arthritis models, one which was induced by collagen one by alkyldiamine. These animal models share several pathological features associated with rheumatoid arthritis. The transition state substrate analog of DP IV, (S)-Alanylpyrrolidine-boronic Acid (Ala-boroPro), suppressed hind paw swelling, which was associated with collagen-induced and alkyldiamine-induced arthritis. A competitive inhibitor of DP IV, Lys(Z(NO2))-thiazolidide and an irreversible inhibitor, Ala-Pro-nitrobenzoylhydroxylamine also suppressed alkyldiamine-induced arthritis dose-dependently. We also analyzed the pharmacological effects of Lys(Z(NO2))-thiazolidide on several immune responses in vitro, in order to determine its mode of action. This inhibitor suppressed mitogen-induced and antigen-induced proliferation of T cells. However, studies using splenic cells from DP IV deficient rats showed that the inhibition of lymphocyte proliferation was not exerted through the inhibition of DP IV.

Structure-activity relationships of boronic acid inhibitors of dipeptidyl peptidase IV. 1. Variation of the P2 position of Xaa-boroPro dipeptides

A series of prolineboronic acid (boroPro) containing dipeptides were synthesized and assayed for their ability to inhibit the serine protease dipeptidyl peptidase IV (DPPIV). Inhibitory activity, which requires the (R)-stereoisomer of boroPro in the P1 position, appears to tolerate a variety of L-amino acids in the P2 position. Substitution at the P2 position which is not tolerated include the D-amino acids, alpha,alpha-disubstituted amino acids, and glycine. Specificity against DPPII and proline specific endopeptidase is reported. A correlation between the ability to inhibit DPPIV in cell culture and in the human mixed lymphocyte reaction is demonstrated. A synthesis of prolineboronic acid is reported as well as conditions for generating the fully unprotected boronic acid dipeptides in either their cyclic or acyclic forms.

Is CD26/dipeptidyl peptidase IV a really important molecule in T cell activation of a certain rat strain?

A new monoclonal antibody (MS-7 mAb) was raised to investigate the real role of the membrane-associated molecule CD26/dipeptidyl peptidase IV (DPP IV; EC 3.4.14.5), which transduces activation signals in T cells. A strain of rats which is deficient in DPP IV was used. MS-7 mAb recognized DPP IV (110 kDa) and its 60 kDa fragment, starting at the 281st residue corresponding to the extracellular one comprising the active-site sequence Gly-X-Ser631-X-Gly of DPP IV. MS-7 mAb recognized CD26 on T cells of DPP IV+ rats both before and after mitogen activation. CD26 expression and DPP IV enzyme activity are increased on T cells following their activation; nevertheless, no CD26 was expressed on T cells of DPP IV- rats, and no DPP IV enzyme activity was detected either before or after mitogen activation. In addition, MS-7 mAb inhibited the mitogen-stimulated proliferation of DPP IV+ rats, but did not affect that of DPP IV- rats. These results suggest that CD26/DPP IV is not a necessary molecule in T cell activation, and that there is some other bypass in T cell activation of DPP IV- rats.

CD26/dipeptidyl peptidase IV expression in human lymphomas is restricted to CD30-positive anaplastic large cell and a subset of T-cell non-Hodgkin's lymphomas

CD26 is identical to the cell surface ectoenzyme dipeptidyl peptidase IV (DPPIV). CD26/DPPIV is associated with T-cell activation and proliferation and also may function as an auxiliary adhesion factor. Although CD26/DPPIV has been previously studied on lymphoid populations and on leukemias/lymphomas of B- and T-cell phenotype, little is known about its expression and functional role in some specific types of lymphomas, such as CD30-positive anaplastic large cell (ALC) lymphomas and Hodgkin's disease (HD). A series of 81 lymphoma samples, including 23 cases of HD, 17 cases of CD30-positive ALC lymphomas, 41 cases of other non-Hodgkin's lymphomas (NHL), and a panel of HD- or ALC lymphoma-derived human cell lines were evaluated for CD26/DPPIV expression by enzyme histochemistry and immunohistochemistry on frozen sections and cell smears. CD26/DPPIV protein was expressed on neoplastic cells in 12 of 17 (71%) ALC lymphomas irrespective of their antigenic phenotype and in seven of 15 (47%) T-cell NHLs. In contrast, we did not detect CD26/DPPIV expression in tumor cells from 26 cases of B-cell NHL other than ALC lymphomas or in Reed Sternberg (RS) cells and variants of 21 of 23 HD cases. Accordingly, CD26/DPPIV expression was maintained on the CD30-positive ALC lymphoma cell line Karpas 299, but the molecule was not detected on HD-derived cell lines of B, T, or non-B non-T phenotype. These results may support a new potential tool for the phenotypic separation of ALC lymphomas from HD based on the differential expression of the CD26/DPPIV molecule. Moreover, given the demonstration that CD26/DPPIV is identical to the human adenosine deaminase (ADA) binding protein, it could be speculated that CD26/DPPIV also may function by interacting with ADA to regulate the growth of CD26/DPPIV expressing neoplastic cells in ALC lymphomas.

Antibody binding profile of purified and cell-bound CD26. Designation of BT5/9 and TA5.9 to the CD26 cluster

The CD26 activation antigen (Ag) which is expressed on a subpopulation of human T cells has been characterized as dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5). In this paper, we describe the antibody binding profile of CD26/DPP IV, purified from human peripheral blood lymphocytes. The purified molecule binds to the anti-Ta1, anti-1F7 and anti-134-2C2 monoclonal antibodies (mAb), reported to react with cell-bound CD26 Ag. Among unclustered mAb recognizing T cell antigens, two, anti-BT5/9 and anti-TA5.9 were found to react with purified and cell-bound CD26 Ag. The classification of the BT5/9 Ag, the functional properties of the BT5/9+ T cell subset, as well as the in vivo effect of anti-BT5/9 mAb administration, are re-interpreted in the light of its specificity. Applying the anti-TA5.9 mAb in three color FACS analyses, we demonstrated that CD26+bright cells co-express CD45RO but not HLA-DR and CD38.

Involvement of dipeptidyl peptidase IV in an in vivo immune response

Dipeptidyl peptidase IV (DP IV) is a serine protease that selectively cleaves X-Pro dipeptides from polypeptides and proteins. Among blood cells, this enzyme occurs preferentially on the surface of CD4+ T cells and the amount of enzyme activity increases with T cell activation. In previous work, two potent and specific peptidyl-boronic acid inhibitors of DP IV, Ala-boroPro and Pro-boroPro, were synthesized and Pro-boroPro was shown to suppress antigen-specific proliferative responses of T cells in vitro. In this study, we tested the in vivo effects of these inhibitors. Subcutaneous injection of Ala-boroPro or Pro-boroPro into BALB/c mice inhibited DP IV activity in serum and spleen cell suspensions. Repeated injections of more than 10 micrograms of Ala-boroPro or Pro-boroPro at 12 h intervals maintained in vivo DP IV activity at less than 30% of the normal level. Repeated injections of the inhibitors during the primary, secondary or tertiary immune response to bovine serum albumin (BSA) reduced anti-BSA antibody production. Without inhibitor, immunization with BSA was followed by a temporary decrease in serum DP IV activity and then by enhanced serum enzyme activity after several days. These results provide the first direct evidence that DP IV plays an important role in immune response in vivo.

Characterization of dipeptidyl peptidase IV (CD26) from human lymphocytes

The membrane-bound dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5) has been purified 5,400-fold from human peripheral blood mononuclear cells. The purification procedure included detergent solubilization and successive chromatography on DEAE Sepharose Fast Flow, Con A Sepharose, Cu2+ loaded metal-chelating Sepharose, Sephacryl S-300 High Resolution and Q Sepharose Hiload. The molecular mass of the native, detergent solubilized enzyme estimated by gel filtration was 264.kDa. Chromatofocusing indicated a pI of approximately 5.0. The pI optimum was 8.7. The enzymatic activity of the purified preparation was irreversibly inhibited by N-(H-Phe-Pro)-O-(4-nitrobenzoyl)hydroxylamine hydrochloride in the micromolar range. The binding of purified DPP IV to CD26 monoclonal antibodies confirmed the identity between CD26 and dipeptidyl peptidase IV. The purification and characterization of lymphocytic dipeptidyl peptidase IV is of great value for the identification of its natural substrates and for the study of its physiological significance in the T-lymphocyte function.

The evolution of proteinase substrates with special reference to dipeptidylpeptidase IV

The design and development of specific substrates for proteolytic enzymes is reviewed. Particular attention is given to substrates containing the leaving groups 4-methoxy-2-naphthylamide (MNA) and 7-amino-4-trifluoromethylcoumarin (AFC). The MNA substrates are used for histochemical and cytochemical purposes, and they yield a coloured final reaction product when azo-coupled with a diazonium salt, an osmiophilic product for electron microscopy when coupled with hexazotized Pararosaniline, or a fluorescent final reaction product when coupled with 5-nitrosalicylaldehyde. AFC substrates are considerably more sensitive, and they yield the fluorescent product AFC after enzymatic cleavage of the substrate. AFC is not sufficiently water-insoluble to allow (intra)cellular localization, but AFC substrates are successfully used for incubations in microwells (Immu-Probe technique) and for the demonstration of banding patterns after gel electrophoresis (enzyme-directed overlay membrane technique). The methods are discussed with the example of the elucidation of the role of dipeptidylpeptidase IV in autoimmune diseases.

Distribution of proline-specific aminopeptidases in human tissues and body fluids

The proline-specific peptidases, aminopeptidase P (EC 3.4.11.9) and dipeptidyl peptidase IV (EC 3.4.14.5), were measured in human tissue homogenates and physiological fluids. All tissues examined contained measurable aminopeptidase P and dipeptidyl peptidase IV activities. High specific activities for both enzymes under study were found in benign prostatic hypertrophy. Normal prostate and prostatic adenocarcinoma had a much lower activity. This difference, however, is not reflected in the serum values of the patients. The most striking finding is the extremely high activity of dipeptidyl peptidase IV in prostatosomes, prostate-derived organelles, which occur freely in human seminal plasma, and which are important for enhancement of sperm forward motility.