Significance of N-Terminal Proteolysis of CCL14a to Activity on the Chemokine Receptors CCR1 and CCR5 and the Human Cytomegalovirus-Encoded Chemokine Receptor US28

• Published in: The Journal of immunology (1950) 2009-07, Vol.183 (2), p.1229-1237
• Main Authors: Richter, Rudolf, Casarosa, Paola, Standker, Ludger, Munch, Jan, Springael, Jean-Yves, Nijmeijer, Saskia, Forssmann, Wolf-Georg, Vischer, Henry F, Vakili, Jalal, Detheux, Michel, Parmentier, Marc, Leurs, Rob, Smit, Martine J
• Format: Article
• Language: English
• Subjects: Calcium Signaling; Cell Line; Chemokines, CC - metabolism; Cytomegalovirus; Dipeptidyl Peptidase 4 - metabolism; Fibrinolysin - metabolism; HIV Infections - prevention & control; Humans; Peptide Fragments - chemistry; Peptide Fragments - physiology; Peptide Hydrolases - metabolism; Protein Binding; Receptors, CCR1 - metabolism; Receptors, CCR5 - metabolism; Receptors, Chemokine - metabolism; Urokinase-Type Plasminogen Activator - metabolism; Viral Proteins - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.0802145

The CC chemokine CCL14a is constitutively expressed in a large variety of tissues and its inactive proform CCL14a(1-74) circulates in high concentrations in plasma. CCL14a(1-74) is converted into CCL14a(9-74) by the proteases urokinase-type plasminogen activator and plasmin and is a highly active agonist for the chemokine receptors CCR1 and CCR5. In this study, a new CCL14a analog, CCL14a(12-74), was isolated from blood filtrate. To elucidate the functional role of the N terminus, a panel of N-terminally truncated CCL14a analogs were tested on the receptors CCR1 to CCR5 and on the human cytomegalovirus (HCMV)-encoded chemokine receptor US28. The rank order of binding affinity to these receptors and of the activation of CCR1 and CCR5-mediated intracellular Ca(2+) concentration mobilization is CCL14a(6-74)(12-74). The almost identical affinities of CCL14a(7-74), CCL14a(9-74), and CCL14a(10-74) for the US28 receptor and the inhibition of US28-mediated HIV infection of 293T cells by all of the N-terminally truncated CCL14a analogs support the promiscuous nature of the viral chemokine receptor US28. In high concentrations, CCL14a(12-74) did reveal antagonistic activity on intracellular Ca(2+) concentration mobilization in CCR1- and CCR5-transfected cells, which suggests that truncation of Tyr(11) might be of significance for an efficient inactivation of CCL14a. A putative inactivation pathway of CCL14a(9-74) to CCL14a(12-74) may involve the dipeptidase CD26/dipeptidyl peptidase IV (DPPIV), which generates CCL14a(11-74), and the metalloprotease aminopeptidase N (CD13), which displays the capacity to generate CCL14a(12-74) from CCL14a(11-74). Our results suggest that the activity of CCL14a might be regulated by stringent proteolytic activation and inactivation steps.