title: Identification of IGFBP-3 fragments generated by KLK2 and prevention of fragmentation by KLK2-inhibiting peptides.
abstract: Kallikrein-related peptidase 2 (KLK2) degrades insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) in vitro. IGFBP-3 forms complexes with IGFs, preventing them from binding to their receptors and stimulating cell proliferation and survival. IGF-independent actions have also been described for IGFBP-3. The degradation of IGFBP-3 by KLK2 or other proteases in the prostate may promote the growth of prostate cancer. We studied IGFBP-3 degradation by immunoblotting and two specific immunoassays, one recognizing only native non-fragmented IGFBP-3 and the other one recognizing both intact and proteolytically cleaved IGFBP-3. Peptides were used to inhibit the enzyme activity of KLK2 and cleavage sites in IGFBP-3 were identified by mass spectrometry. KLK2 proteolyzed IGFBP-3 into several small fragments, mostly after Arg residues, in keeping with the trypsin-like activity of KLK2. The fragmentation could be inhibited by KLK2-inhibiting peptides in a dose-dependent fashion. As degradation of IGFBP-3 could lead to a more aggressive cancer phenotype, inhibition of KLK2 activity might be useful for treatment of prostate cancer and other diseases associated with increased KLK2 activity.
authors.affiliation: Department of Clinical Chemistry, Biomedicum Helsinki, University of Helsinki and Helsinki University Central Hospital, Finland.
authors.forename: Can
authors.initials: C
authors.lastname: Hekim
authors.forename: Tero
authors.initials: T
authors.lastname: Riipi
authors.forename: Janne
authors.initials: J
authors.lastname: Weisell
authors.forename: Ale
authors.initials: A
authors.lastname: Närvänen
authors.forename: Riitta
authors.initials: R
authors.lastname: Koistinen
authors.forename: Ulf-Håkan
authors.initials: UH
authors.lastname: Stenman
authors.forename: Hannu
authors.initials: H
authors.lastname: Koistinen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015200:Fluoroimmunoassay; D006801:Humans; D015151:Immunoblotting; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D020840:Tissue Kallikreins / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments; D010455:Peptides; D015842:Serine Proteinase Inhibitors; D020840:Tissue Kallikreins