title: Inducible expression of tissue inhibitor of metalloproteinases-resistant matrix metalloproteinase-9 on the cell surface of neutrophils.
abstract: Matrix metalloproteinase (MMP)-9 secreted by activated polymorphonuclear neutrophils (PMN) may play roles in mediating lung injury by degrading extracellular matrix proteins. However, the mechanisms by which MMP-9 retains activity in the presence of tissue inhibitors of metalloproteinases (TIMPs) are not known. We show that MMP-9 is also expressed on the cell surface of PMN, and proinflammatory mediators induce up to 10-fold increases in cell surface expression of MMP-9. Stimulated human PMN express active forms of cell surface MMP, which cleave the MMP substrate, McaPLGLDpaAR. Loss-of-function studies employing PMN from mice genetically deficient in MMP-9 (MMP-9-/-) demonstrate that membrane-bound MMP-9 contributes substantially to MMP-mediated surface-bound cleavage of McaPLGLDpaAR (approximately 50%) and gelatin (approximately 70%) by stimulated PMN. Like soluble MMP-9, membrane-bound MMP-9 cleaves McaPLGLDpaAR (Kcat/KM = 82,000 M-1s-1), gelatin, type IV collagen, elastin, and alpha1-proteinase inhibitor. However, in contrast to soluble MMP-9, membrane-bound MMP-9 is substantially resistant to inhibition by TIMPs. The IC50 for inhibition of membrane-bound MMP-9 by TIMP-1 and TIMP-2 are approximately 21-fold and approximately 68-fold higher, respectively, than those for inhibition of soluble MMP-9. The binding of MMP-9 to the plasma membrane of PMN enables it to evade inhibition by TIMPs, and thereby may alter the pericellular proteolytic balance in favor of extracellular matrix degradation. Membrane-bound MMP-9 on PMN may play pathogenetic roles in inflammatory lung diseases.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. cowen@rics.bwh.harvard.edu
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Owen
authors.forename: Zhuma
authors.initials: Z
authors.lastname: Hu
authors.forename: Brooke
authors.initials: B
authors.lastname: Barrick
authors.forename: Steven D
authors.initials: SD
authors.lastname: Shapiro
mesh_terms: D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology* / Q000378:metabolism; D024141:Collagen Type IV / Q000096:biosynthesis; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004549:Elastin / Q000096:biosynthesis; D005780:Gelatin / Q000737:chemistry; D006801:Humans; D007249:Inflammation; D020128:Inhibitory Concentration 50; D007700:Kinetics; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism; D011485:Protein Binding; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases / Q000096:biosynthesis*
chemical_list: D024141:Collagen Type IV; D016207:Cytokines; D019715:Tissue Inhibitor of Metalloproteinase-1; D019714:Tissue Inhibitor of Metalloproteinases; D019716:Tissue Inhibitor of Metalloproteinase-2; D009240:N-Formylmethionine Leucyl-Phenylalanine; D005780:Gelatin; D004549:Elastin; D020780:Matrix Metalloproteinase 9