Christine Durinx

Dipeptidyl-Peptidase IV from Bench to Bedside: An Update on Structural Properties, Functions, and Clinical Aspects of the Enzyme DPP IV

Dipeptidyl-peptidase IV/CD26 (DPP IV) is a cell-surface protease belonging to the prolyloligopeptidase family. It selectively removes the N-terminal dipeptide from peptides with proline or alanine in the second position. Apart from its catalytic activity, it interacts with several proteins, for instance, adenosine deaminase, the HIV gp120 protein, fibronectin, collagen, the chemokine receptor CXCR4, and the tyrosine phosphatase CD45. DPP IV is expressed on a specific set of T lymphocytes, where it is up-regulated after activation. It is also expressed in a variety of tissues, primarily on endothelial and epithelial cells. A soluble form is present in plasma and other body fluids. DPP IV has been proposed as a diagnostic or prognostic marker for various tumors, hematological malignancies, immunological, inflammatory, psychoneuroendocrine disorders, and viral infections. DPP IV truncates many bioactive peptides of medical importance. It plays a role in glucose homeostasis through proteolytic inactivation of the incretins. DPP IV inhibitors improve glucose tolerance and pancreatic islet cell function in animal models of type 2 diabetes and in diabetic patients. The role of DPP IV/CD26 within the immune system is a combination of its exopeptidase activity and its interactions with different molecules. This enables DPP IV/CD26 to serve as a co-stimulatory molecule to influence T cell activity and to modulate chemotaxis. DPP IV is also implicated in HIV-1 entry, malignant transformation, and tumor invasion. Referee: Dr. Albert Adam, Faculté de Pharmace, Université de Montréal, 2900 Blvd. Edouard—Montpetit, CP succursale Centreville, Montreal, Quebec H3C 3J7, Canada

Processing by CD26/dipeptidyl-peptidase IV reduces the chemotactic and anti-HIV-1 activity of stromal-cell-derived factor-1α

The chemokine stromal‐cell‐derived factor‐1α (SDF‐1α) chemoattracts lymphocytes and CD34+ haematopoietic progenitors and is the ligand for CXCR4 (CXC chemokine receptor 4), the main co‐receptor for T‐tropic HIV‐1 strains. SDF‐1α was NH2‐terminally cleaved to SDF‐1α(3‐68) by dipeptidyl‐peptidase IV (CD26/DPP IV), which is present in blood in soluble and membrane‐bound form. SDF‐1α(3‐68) lost both lymphocyte chemotactic and CXCR4‐signaling properties. However, SDF‐1α(3‐68) still desensitized the SDF‐1α(1‐68)‐induced Ca2+ response. In contrast to CD26/DPP IV‐processed RANTES(3‐68), SDF‐1α(3‐68) had diminished potency to inhibit HIV‐1 infection. Thus, CD26/DPP IV impairs the inflammatory and haematopoietic potency of chemokines but plays a dual role in AIDS.

Kinetic study of the processing by dipeptidyl-peptidase IV/CD26 of neuropeptides involved in pancreatic insulin secretion

Dipeptidyl‐peptidase IV (DPPIV/CD26) metabolizes neuropeptides regulating insulin secretion. We studied the in vitro steady‐state kinetics of DPPIV/CD26‐mediated truncation of vasoactive intestinal peptide (VIP), pituitary adenylyl cyclase‐activating peptide (PACAP27 and PACAP38), gastrin‐releasing peptide (GRP) and neuropeptide Y (NPY). DPPIV/CD26 sequentially cleaves off two dipeptides of VIP, PACAP27, PACAP38 and GRP. GRP situates between the best DPPIV/CD26 substrates reported, comparable to NPY. Surprisingly, the C‐terminal extension of PACAP38, distant from the scissile bond, improves both PACAP38 binding and turnover. Therefore, residues remote from the scissile bond can modulate DPPIV/CD26 substrate selectivity as well as residues flanking it.

Natural substrates of dipeptidyl peptidase IV

During the last decade it has become clear that DPP IV may have various substrates in vivo and that the preferred peptide will depend on the localization and physiological circumstances. It is at present impossible to depict a certain chain length as the maximal acceptable substrate size as it turns out that the immediate surrounding and surface accessibility of the NH2-terminal dipeptide are determining the susceptibility for cleavage of a peptide.

Reference Values for Plasma Dipeptidyl Peptidase IV Activity and Their Association with Other Laboratory Parameters

Abstract In blood, the exopeptidase dipeptidyl-peptidase IV (DPPIV; EC 3.4.14.5) is predominantly present in a soluble form in plasma/serum and as an activation antigen on the membrane of lymphocytes (CD26). It modifies some important biologically active peptides (neuropeptides, chemokines), and a regulatory role for DPPIV/CD26 in immune and endocrine processes has been demonstrated. The aim of this study was to determine reference values for plasma/serum DPPIV activity and to study the association of this activity with a series of biochemical and hematological parameters and baseline characteristics such as age, gender, blood pressure and body mass index. We studied 481 healthy subjects aged between 19 and 61 years. The group consisted of 213 men and 268 women equally divided between the different categories of age. Among the women, 127 were taking hormone therapy (contraception/hormone replacement) and 141 were not. A multiple regression model shows that DPPIV activity decreases significantly with age. The activity in women is slightly lower than in men. We observed an important association with liver, muscle and lipid metabolism-related parameters. In this model, no significant contribution of body mass index, blood pressure or hormone therapy could be stated.

Lowered serum dipeptidyl peptidase IV activity in patients with anorexia and bulimia nervosa.

Abstract The aim of this study was to examine whether anorexia nervosa and bulimia nervosa are accompanied by lower serum activity of dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5), a membrane-bound serine protease that catalyses the cleavage of dipeptides from the amino-terminus of oligo- and polypeptides. Substrates of DPP IV are, amongst others, neuroactive eptides, such as substance P, growth hormone releasing hormone, neuropeptide Y, and peptide YY. DPP IV activity was measured in the serum of 21 women with anorexia nervosa, 21 women with bulimia nervosa and 18 normal women. Serum ¶DPP IV activity was significantly lower in patients with anorexia nervosa and bulimia nervosa than in the normal controls. In the total study group, there were significant and inverse relationships between serum DPP IV activity and the total scores on the Bulimic Investigatory Test, Edinburgh, the Eating Disorder Inventory (EDI) and the Hamilton Depression Rating Scale. In the total study group no significant correlations between DPP IV and age, body weight or body mass index could be found. It is concluded that lowered serum DPP IV activity takes part in the pathophysiology of anorexia and bulimia nervosa. It is hypothesised that a combined dysregulation of DPP IV and neuroactive peptides, which are substrates of DPP IV, e.g. neuropeptide Y and peptide YY, could be an integral component of eating disorders.

Identifying ELIXIR Core Data Resources

The core mission of ELIXIR is to build a stable and sustainable infrastructure for biological information across Europe. At the heart of this are the data resources, tools and services that ELIXIR offers to the life-sciences community, providing stable and sustainable access to biological data. ELIXIR aims to ensure that these resources are available long-term and that the life-cycles of these resources are managed such that they support the scientific needs of the life-sciences, including biological research. ELIXIR Core Data Resources are defined as a set of European data resources that are of fundamental importance to the wider life-science community and the long-term preservation of biological data. They are complete collections of generic value to life-science, are considered an authority in their field with respect to one or more characteristics, and show high levels of scientific quality and service. Thus, ELIXIR Core Data Resources are of wide applicability and usage. This paper describes the structures, governance and processes that support the identification and evaluation of ELIXIR Core Data Resources. It identifies key indicators which reflect the essence of the definition of an ELIXIR Core Data Resource and support the promotion of excellence in resource development and operation. It describes the specific indicators in more detail and explains their application within ELIXIR’s sustainability strategy and science policy actions, and in capacity building, life-cycle management and technical actions. The identification process is currently being implemented and tested for the first time. The findings and outcome will be evaluated by the ELIXIR Scientific Advisory Board in March 2017. Establishing the portfolio of ELIXIR Core Data Resources and ELIXIR Services is a key priority for ELIXIR and publicly marks the transition towards a cohesive infrastructure.

Presence and release of SR-17 (chromogranin B586-602) in the porcine splenic nerve and its enzymatic degradation by CD26/dipeptidyl peptidase IV

Using the pig splenic nerve as a model, we investigated the proteolytic processing of porcine chromogranin B (CgB) during its axonal transport. An ELISA was developed for SR-17 (CgB(586-602)), a novel CgB-derived peptide, originally found in the adrenal medulla. The results demonstrate that CgB is processed in an early stage during its axonal transport. Immunohistochemical data, based on a rabbit anti-SR-17 antiserum, show that the spleen CgB/SR-17 is exclusively present in the nerve endings. No SR-17 immunoreactivity (IR) was found in splenocytes. We also provide evidence that SR-17 is co-released with noradrenaline (NA) upon electrical stimulation of the splenic nerve. Its release is frequency-dependent and strongly enhanced in the presence of the alpha-blocking agent phentolamine. In addition, we show that the new CgB-peptide can serve as a substrate for the lymphocyte surface glycoprotein CD26, also known as dipeptidyl peptidase IV (DPP IV), generating a new peptide ER-15 (CgB(588-602)).

DPIV — Natural Substrates of Medical Importance

In a continuing attempt to unravel the in vivo function of this abundant but highly regulated enzyme, the hydrolysis of bioactive peptides by DPIV has been studied extensively (Mentlein 1999). This chapter focuses on recent data concerning a number of human naturally occurring peptides that are cleaved by DPIV in vitro and that may be substrates in vivo. A summary of the kinetic parameters of the processing by DPIV can be found at the end of this chapter.

TOWARDS COORDINATED INTERNATIONAL SUPPORT OF CORE DATA RESOURCES FOR THE LIFE SCIENCES

On November 18-19, 2016, the Human Frontier Science Program Organization (HFSPO) hosted a meeting of senior managers of key data resources and leaders of several major funding organizations to discuss the challenges associated with sustaining biological and biomedical (i.e., life sciences) data resources and associated infrastructure. A strong consensus emerged from the group that core data resources for the life sciences should be supported through a coordinated international effort(s) that better ensure long-term sustainability and that appropriately align funding with scientific impact. Ideally, funding for such data resources should allow for access at no charge, as is presently the usual (and preferred) mechanism. Below, the rationale for this vision is described, and some important considerations for developing a new international funding model to support core data resources for the life sciences are presented.