title: Differential Processing of {alpha}- and {beta}-Defensin Precursors by Matrix Metalloproteinase-7 (MMP-7).
abstract: Proteolytic processing of defensins is a critical mode of posttranslational regulation of peptide activity. Because mouse alpha-defensin precursors are cleaved and activated by matrix metalloproteinase-7 (MMP-7), we determined if additional defensin molecules, namely human neutrophil defensin pro-HNP-1 and beta-defensins, are targets for MMP-7. We found that MMP-7 cleaves within the pro-domain of the HNP-1 precursor, a reaction that does not generate the mature peptide but produces a 59-amino acid intermediate. This intermediate, which retains the carboxyl-terminal end of the pro-domain, had antimicrobial activity, indicating that the residues important for masking defensin activity reside in the amino terminus of this domain. Mature HNP-1 was resistant to processing by MMP-7 unless the peptide was reduced and alkylated, demonstrating that only the pro-domain of alpha-defensins is normally accessible for cleavage by this enzyme. From the 47-residue HBD-1 precursor, MMP-7 catalyzed removal of 6 amino acids from the amino terminus. Neither a 39-residue intermediate form of HBD-1 nor the mature 36-residue form of HBD-1 was cleaved by MMP-7. In addition, both pro-HBD-2, with its shorter amino-terminal extension, and pro-HBD-3 were resistant to MMP-7. However, human and mouse beta-defensin precursors that lack disulfide bonding contain a cryptic MMP-7-sensitive site within the mature peptide moiety. These findings support and extend accumulating evidence that the native three-dimensional structure of both alpha- and beta-defensins protects the mature peptides against proteolytic processing by MMP-7. We also conclude that sites for MMP-7 cleavage are more common at the amino termini of alpha-defensin rather than beta-defensin precursors, and that catalysis at these sites in alpha-defensin pro-domains results in acquisition of defensin activity.
authors.affiliation: Department of Pathology and Center for Lung Biology, University of Washington, Seattle, Washington 98104, USA. carolew2@u.washington.edu
authors.forename: Carole L
authors.initials: CL
authors.lastname: Wilson
authors.forename: Amy P
authors.initials: AP
authors.lastname: Schmidt
authors.forename: Emma
authors.initials: E
authors.lastname: Pirilä
authors.forename: Erika V
authors.initials: EV
authors.lastname: Valore
authors.forename: Nicola
authors.initials: N
authors.lastname: Ferri
authors.forename: Timo
authors.initials: T
authors.lastname: Sorsa
authors.forename: Tomas
authors.initials: T
authors.lastname: Ganz
authors.forename: William C
authors.initials: WC
authors.lastname: Parks
mesh_terms: D000818:Animals; D002384:Catalysis; D002460:Cell Line; D006801:Humans; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism*; D051379:Mice; D011498:Protein Precursors / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D023084:alpha-Defensins / Q000378:metabolism*; D023083:beta-Defensins / Q000378:metabolism*
chemical_list: C406407:DEFB1 protein, human; C106641:DEFB4A protein, human; D011498:Protein Precursors; D023084:alpha-Defensins; D023083:beta-Defensins; C406413:human neutrophil peptide 1; C060932:MMP7 protein, human; D020783:Matrix Metalloproteinase 7