Dipeptidyl peptidase IV (CD26) activity in the hematopoietic system: differences between the membrane-anchored and the released enzyme activity

Abstract

Dipeptidyl peptidase IV (DPP-IV; CD26) (EC 3.4.14.5) is a membrane-anchored ectoenzyme with N-terminal exopeptidase activity that preferentially cleaves X-Pro-dipeptides. It can also be spontaneously released to act in the extracellular environment or associated with the extracellular matrix. Many hematopoietic cytokines and chemokines contain DPP-IV-susceptible N-terminal sequences. We monitored DPP-IV expression and activity in murine bone marrow and liver stroma cells which sustain hematopoiesis, myeloid precursors, skin fibroblasts, and myoblasts. RT-PCR analysis showed that all these cells produced mRNA for DPP-IV. Partially purified protein reacted with a commercial antibody to CD26. The K M values for Gly-Pro-p-nitroanilide ranged from 0.43 to 0.98 mM for the membrane-associated enzyme of connective tissue stromas, and from 6.76 to 8.86 mM for the enzyme released from the membrane, corresponding to a ten-fold difference, but only a two-fold difference in K M was found in myoblasts. K M of the released soluble enzyme decreased in the presence of glycosaminoglycans, nonsulfated polysaccharide polymers (0.8-10 µg/ml) or simple sugars (320-350 µg/ml). Purified membrane lipid rafts contained nearly 3/4 of the total cell enzyme activity, whose K M was three-fold decreased as compared to the total cell membrane pool, indicating that, in the hematopoietic environment, DPP-IV activity is essentially located in the lipid rafts. This is compatible with membrane-associated events and direct cell-cell interactions, whilst the long-range activity depending upon soluble enzyme is less probable in view of the low affinity of this form

The Long Noncoding RNA SPRIGHTLY Regulates Cell Proliferation in Primary Human Melanocytes

“…Although the exact mechanism by which SPRIGHTLY regulates DPPIV/CD26 remains to be determined, DPPIV/CD26 has been reported to be regulated at the transcriptional level by promoter methylation, interferons, and retinoic acid (Bauvois et al, 2000) and at the protein level by post-translational events (Pereira et al, 2003; Swenson, 2007). Here, DPPIV promoter CpG islands were examined for possible promoter hypermethylation; however, no aberrant CpG island methylation was identified.…”

SDF-1 dynamically mediates megakaryocyte niche occupancy and thrombopoiesis at steady state and following radiation injury

“…For the stabilization of endogenous SDF-1, we used tripeptide Diprotin A to inhibit DPP4, a peptidase that inactivates SDF-1. 66,75 This strategy has been used to stabilize SDF-1 in several contexts, including the homing and engraftment of hematopoietic stem cells and the recruitment of marrow-derived progenitors to sites of cardiac ischemia for myocardial regeneration. 68,[76][77][78] DPP4 was recently shown to truncate several cytokines, including IL-6, and is predicted to truncate TPO.…”

“…63,64 To stabilize endogenously-produced SDF-1, we used Diprotin A, a small peptide that inhibits dipeptidyl peptidase 4 (DPP4), a soluble and cell-surface protease present in the bone marrow that truncates SDF-l and abolishes its chemotactic activity. [65][66][67][68] There were no changes in the number of marrow MKPs or MKs by 24 hours after administration of Diprotin A; however, there was a 20% increase in circulating platelets (Figure 2A). Similar to the response of MKs to exogenous SDF-1 ( Figure 1F), marrow MKs had increased surface CXCR4 1 hour after Diprotin A-mediated stabilization of SDF-1 ( Figure 2B).…”

Upregulation of CD26 expression in epithelial cells and stromal cells during wound-induced skin tumour formation

“…After removal of feeders, keratinocytes were washed with buffer-1 (0.1 M Tris-HCl, pH 7.4). Buffer-1 containing 1 mM GlycineProline-p-Nitroanilide (Gly-Pro-pNA) substrate was added to the samples and incubated at 37 1C for 2 h (Pereira et al, 2003). 1 M acetate buffer (pH 4.4) stopped the reaction.…”