title: Identification of membrane-bound serine proteinase matriptase as processing enzyme of insulin-like growth factor binding protein-related protein-1 (IGFBP-rP1/angiomodulin/mac25).
abstract: Insulin-like growth factor (IGF) binding protein-related protein-1 (IGFBP-rP1) modulates cellular adhesion and growth in an IGF/insulin-dependent or independent manner. It also shows tumor-suppressive activity in vivo. We recently found that a single-chain IGFB-rP1 is proteolytically cleaved to a two-chain form by a trypsin-like, endogenous serine proteinase, changing its biological activities. In this study, we attempted to identify the IGFBP-rP1-processing enzyme. Of nine human cell lines tested, seven cell lines secreted IGFBP-rP1 at high levels, and two of them, ovarian clear cell adenocarcinoma (OVISE) and gastric carcinoma (MKN-45), highly produced the cleaved IGFBP-rP1. Serine proteinase inhibitors effectively blocked the IGFBP-rP1 cleavage in the OVISE cell culture. The conditioned medium of OVISE cells did not cleave purified IGFBP-rP1, but their membrane fraction had an IGFBP-rP1-cleaving activity. The membrane fraction contained an 80-kDa gelatinolytic enzyme, which was identified as the membrane-type serine proteinase matriptase (MT-SP1) by immunoblotting. When the membrane fraction was separated by SDS/PAGE, the IGFBP-rP1-cleaving activity comigrated with matriptase. A soluble form of matriptase purified in an inhibitor-free form efficiently cleaved IGFBP-rP1 at the same site as that found in a naturally cleaved IGFBP-rP1. Furthermore, small interfering RNAs for matriptase efficiently blocked both the matriptase expression and the cleavage of IGBP-rP1 in OVISE cells. These results demonstrate that IGFBP-rP1 is processed to the two-chain form by matriptase on the cell surface.
authors.affiliation: Division of Cell Biology, Kihara Institute for Biological Research, Yokohama City University, Japan.
authors.forename: Sanjida
authors.initials: S
authors.lastname: Ahmed
authors.forename: Xinlian
authors.initials: X
authors.lastname: Jin
authors.forename: Motoki
authors.initials: M
authors.lastname: Yagi
authors.forename: Chie
authors.initials: C
authors.lastname: Yasuda
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Sato
authors.forename: Shouichi
authors.initials: S
authors.lastname: Higashi
authors.forename: Chen-Yong
authors.initials: CY
authors.lastname: Lin
authors.forename: Robert B
authors.initials: RB
authors.lastname: Dickson
authors.forename: Kaoru
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D034741:RNA, Small Interfering; C102529:insulin-like growth factor binding protein-related protein 1; D012697:Serine Endopeptidases; C485596:ST14 protein, human