CELL-TYPE-SPECIFIC REGULATION OF SL-1 AND SL-2 GENES - INDUCTION OF THE SL-2 GENE BUT NOT THE SL-1 GENE BY HUMAN KERATINOCYTES IN RESPONSE TO CYTOKINES AND PHORBOLESTERS

The stromelysin-2 (SL-2) gene is transcriptionally active in normal hu man keratinocytes and encodes a secreted, catalytically competent but latent matrix metalloproteinase. Phorbolester induction resulted in th e emergence of SL-2 (but not SL-1 transcripts), whereas the opposite w as true for human mucosal fibroblasts. Expression of keratinocyte SL-2 was also induced by the two keratinocyte growth factors, transforming growth factor-alpha and epidermal growth factor, by the proinflammato ry cytokine, tumor necrosis factor-alpha, but, somewhat surprisingly, not by interleukin-1beta. The latent SL-2 proenzyme was isolated from 12-O-tetradecanoylphorbol-13-acetate-induced keratinocytes by immunoaf finity chromatography using a cross-reactive antibody raised against h uman SL-1. This procedure led to the recovery of a single M(r) 54,000 molecular species at a level of almost-equal-to 0.2 mug/ml of culture medium. Amino-terminal sequencing identified the protein as SL-2 and v erified the predicted signal sequence cleavage site. Conformational ac tivation of latent SL-2 precursor by SDS gave rise to a full-length, u ncleaved (M(r) 54,000) active form and at the same time exposed a cryp tic thiol group. By contrast, organomercurial activation resulted in a utolytic truncation of the molecule with loss of M(r) almost-equal-to 10,000 propeptide. SL-2 shared with (human fibroblast) SL-1 the abilit y to cleave casein, to ''superactivate'' fibroblast type procollagenas e, and to form apparently binary, SDS-resistant complexes with tissue inhibitor of metalloproteinases-1.