PARTIAL CHARACTERIZATION OF MATRIX-ASSOCIATED SERINE-PROTEASE INHIBITORS FROM HUMAN SKIN CELLS

Serine protease inhibitors have important regulatory roles in angiogen esis, intravascular fibrinolysis, wound healing, and cell migration, I n this study, the extracellular matrix secreted by cultured human kera tinocytes, foreskin fibroblasts, and SV-40-transformed human skin fibr oblasts was analyzed for serine protease inhibitors by substrate rever se zymography. We found that the extracellular matrix deposited by the se cells contained three inhibitors (Mr 33,000, 31,000, and 27,000), T hese inhibitors protected the degradation of gelatin by trypsin and el astase, and of casein by plasmin. In contrast, the gelatinolytic activ ities of thermolysin and papain were not inhibited. Compared to untrea ted cells, cells treated with phorbol 12-myristate 13-acetate showed a two- to 10-fold increase in the expression of these inhibitors, Cyclo heximide and actinomycin D decreased the cellular expression of these inhibitors, suggesting the involvement of de novo protein and mRNA syn thesis, Antitrypsin activity of these inhibitors was resistant to heat and sodium dodecylsulfate, but was lost after reduction of disulfide bonds, The inhibitors bound specifically to trypsin and could be elute d from a trypsin column in active form, Collectively, these data sugge st that the extracellular matrix deposited by keratinocytes and dermal fibroblasts contains active serine protease inhibitors.