DEGRADATION OF FIBRONECTIN FIBRILS BY MATRILYSIN AND CHARACTERIZATIONOF THE DEGRADATION PRODUCTS

Matrilysin is a metalloproteinase expressed in a variety of tumors as well as in some types of normal tissue. In addition to regulating norm al tissue remodeling, metalloproteinases are believed to play a role i n tumor cell invasion and metastasis by degrading components of the ex tracellular matrix, for example the highly insoluble fibronectin fibri ls found in the interstitial stroma. In this study we examined whether matrilysin can degrade fibronectin fibrils produced by human foreskin fibroblasts and characterized the degradation products of soluble fib ronectin. Using indirect immunofluorescence microscopy, we demonstrate for the first time degradation of the fibronectin fibrils upon incuba tion with 15 nM active matrilysin. Removal of matrilysin resulted in r egrowth of the fibrils, suggesting that matrilysin was not cytotoxic. Immunoblotting with specific monoclonal antibodies revealed initial de gradation of soluble fibronectin within 1 h. Further degradation occur red over a period of 20 h. Degradation of soluble fibronectin resulted in one fragment of 58 kDa containing the gelatin-binding domain, two fragments of 37 and 38 kDa, which were part of the cell attachment dom ain, and three fragments of 36, 33, and 30 kDa recognized by an antibo dy raised against the C-terminal heparin-binding domain. In addition t o most of these fragments, several intermediates and unique fragments of 31 and 34 kDa could be found in the conditioned medium of human for eskin fibroblasts treated with matrilysin. Isolation of these fragment s may allow further studies to determine their influences on cell migr ation, attachment, and signal transduction, which are expected to be d ifferent from the effects of undegraded fibronectin. (C) 1995 Academic Press, Inc.