Urokinase plasminogen activator and plasmin efficiently convert hemofiltrate CC chemokine 1 into its active [9-74] processed variant

We have previously isolated from human hemofiltrate an N-terminally truncat ed form of the hemofiltrate CC chemokine 1 (HCC-1), and characterized HCC-1 [9-74] as a strong agonist of CCR1, CCR5, and to a lower extent CCR3. In th is study, we show that conditioned media from human tumor cell lines PC-3 a nd 143B contain proteolytic activities that convert HCC-I into the [9-74] f orm. This activity was fully inhibited by inhibitors of urokinase-type plas minogen activator (uPA), including PA inhibitor-1, an anti-uPA mAb, and ami loride. Pure preparations of uPA processed HCC-1 with high efficiency, with out further degrading HCC-1[9-74]. Plasmin could also generate HCC-1[9-74], but degraded the active product as well. The kinetics of HCC-I cleavage by uPA and plasmin (Michaelis constant, K-m, of 0.76 +/- 0.4 muM for uPA, and 0.096 +/- 0.05 muM for plasmin; catalytic rate constant, k(cnt): 3.36 +/- 0.96 s(-1) for uPA and 6 +/- 3.6 s(-1) for plasmin) are fully compatible wi th a role in vivo. The activation of an abundant inactive precursor into a broad-spectrum chemokine by uPA and plasmin directly links the production o f uPA by numerous tumors and their ability to recruit mononuclear leukocyte s, without the need for the transcriptional activation of chemokine genes.