title: Protease nexin I, a serpin, inhibits plasminogen-dependent degradation of muscle extracellular matrix.
abstract: Clonal, fusing, mouse skeletal muscle cells (C2) were grown to the myotube stage (90% confluence) before they were subjected to isotope-containing serum-free media (3H-proline or 35S-methionine). C2 myotubes secrete and organize a biosynthetically labeled matrix which adheres to the plastic after removal of myotubes with detergent and ammonium hydroxide. When these homotypic-labeled myotube matrices were incubated with myoblast-conditioned media containing high specific activity urokinase-type plasminogen activator, slow, but clearly detectable, release of label occurred. However, degradation of matrix, with solubilization of label, was accelerated sixfold by addition of human plasminogen to diluted myoblast-conditioned media. If protease nexin I, a cellular serine protease inhibitor purified from human fibroblast-conditioned media, was added (0.2 microgram/ml) with plasminogen, inhibition of matrix hydrolysis by 52% occurred. Higher concentrations (0.8 microgram/ml or above) of protease nexin 1 completely inhibited the degradation of extracellular matrix components. A similar protease inhibitor was purified from C2 myotube-conditioned media, and this molecule also inhibited the plasminogen-dependent release of extracellular matrix. We propose that protease nexin 1 inhibits the destruction of myotube matrix by inactivating the plasmin/plasminogen activation system and may be the physiologic regulator of this system during muscle development in vivo.
authors.affiliation: Neurobiology Research Laboratory, University of Kansas, Kansas City, Missouri.
authors.forename: J S
authors.initials: JS
authors.lastname: Rao
authors.forename: C B
authors.initials: CB
authors.lastname: Kahler
authors.forename: J B
authors.initials: JB
authors.lastname: Baker
authors.forename: B W
authors.initials: BW
authors.lastname: Festoff
mesh_terms: D016564:Amyloid beta-Protein Precursor; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D066298:In Vitro Techniques; D051379:Mice; D009132:Muscles / Q000378:metabolism*; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015849:Plasminogen Inactivators; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D012038:Regeneration; D012697:Serine Endopeptidases / Q000378:metabolism; D058258:Serpin E2
chemical_list: D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D015849:Plasminogen Inactivators; D058255:Protease Nexins; D011956:Receptors, Cell Surface; C545486:SERPINE2 protein, human; D058258:Serpin E2; D010960:Plasminogen Activators; D012697:Serine Endopeptidases