Amino-terminal truncation of CXCR3 agonists impairs receptor signaling andlymphocyte chemotaxis, while preserving antiangiogenic properties

The interferon (IFN)-inducible chemokines, specifically, IFN-gamma -inducib le protein-10 (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducib le T-cell alpha -chemoattractant (I-TAC), share a unique CXC chemokine rece ptor (CXCR3). Recently, the highly specific membrane-bound protease and lym phocyte surface marker CD26/dipeptidyl peptidase IV (DPP IV) was found to b e responsible for posttranslational processing of chemokines. Removal of NH 2-terminal dipeptides by CD26/ DPP IV alters chemokine receptor binding and signaling, and hence inflammatory and anti-human immunodeficiency virus (H IV) activities. CD26/DPP IV and CXCR3 are both markers for Th1 lymphocytes and, moreover, CD26/DPP IV is present in a soluble, active form in human pl asma. This study reports that at physiologic enzyme concentrations CD26/DPP IV cleaved 50% of I-TAC within 2 minutes, whereas for IP-10 and Mig the ki netics were 3- and 10-fold slower, respectively. Processing of IP-10 and I- TAC by CD26/ DPP IV resulted in reduced CXCR3-binding properties, loss of c alcium-signaling capacity through CXCR3, and more than 10-fold reduced chem otactic potency. Moreover, IP-10 and I-TAC cleaved by CD26/DPP IV acted as chemotaxis antagonists and CD26/DPP IV-truncated IP-10 and Mig retained the ir ability to Inhibit the angiogenic activity of Interleukin-8 in the rabbi t cornea micropocket model. These data demonstrate a negative feedback regu lation by CD26/DPP IV In CXCR3. mediated chemotaxis without affecting the a ngiostatic potential of the CXCR3 ligands IP-10 and Mig. (C) 2001 by The Am erican Society of Hematology.