MMP-1, -9, and -12 processing of murine ELR⁺ CXC chemokines. (A) Analysis of MMP-12 proteolysis of murine CXCL1, 2, and 3 with or without 1 μmol/L prinomastat (MMPI) as a control on a silver-stained 15% Tris-Tricine SDS-PAGE gel with arrows indicating cleaved chemokine. Black horizontal lines separate individual gels. (B) Identification of human and murine MMP-12 cleavage products by MALDI-TOF MS. Deconvolution of mass spectrometry data revealed that MMP-12 cleaved 3 murine ELR⁺ CXC chemokines in the ELR motif. Cleavage products generated by proteolysis within the ELR motif are highlighted in bold. Arrows indicate human and murine MMP-12 cleavage sites. (C) Tris-Tricine 15% SDS-PAGE gel analysis of MMP-1 and -9 cleavage of murine CXCL1, -2, -3, and -5 with arrows indicating cleaved chemokine. MMP-12 cleavage products are shown for comparison. Black horizontal lines separate individual gels. (D) Identification of human MMP-1 and -9 cleavage products by MALDI-TOF MS. Deconvolution of mass spectrometry data revealed that only MMP-9 cleaved one murine ELR⁺ CXC chemokine in the ELR motif. Cleavage products generated by proteolysis within the ELR motif are highlighted in bold. Arrows indicate MMP-1 or -9 cleavage sites.