Identification of membrane-bound serine proteinase matriptase as processing enzyme of insulin-like growth factor binding protein-related protein-1 (IGFBP-rP1/angiomodulin/mac25)

FEBS J. 2006 Feb;273(3):615-27. doi: 10.1111/j.1742-4658.2005.05094.x.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Line, Tumor
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Insulin-Like Growth Factor Binding Proteins / drug effects
  • Insulin-Like Growth Factor Binding Proteins / metabolism*
  • RNA, Small Interfering / pharmacology
  • Serine Endopeptidases / drug effects
  • Serine Endopeptidases / metabolism*
  • Structure-Activity Relationship
  • Tumor Cells, Cultured


  • Insulin-Like Growth Factor Binding Proteins
  • RNA, Small Interfering
  • insulin-like growth factor binding protein-related protein 1
  • Serine Endopeptidases
  • ST14 protein, human