Leukoregulin, A T‐cell derived cytokine, upregulates stromelysin‐1 gene expression in human dermal fibroblasts: Evidence for the role of AP‐1 in transcriptional activiation

Leukoregulin (LR), a product of activated T-cells, has been recently shown to modulate the metabolism of extracellular matrix components in human skin fibroblast cultures (Mauviel et al., J Cell Biol 113:1455-1462, 1991). In this study we focused our attention on the effects of LR on the expression of stromelysin-1 gene. This matrix metalloprotease has a broad spectrum of degradative activity and it is also required for maximal activation of interstitial collagenase. Incubation of skin fibroblast cultures with LR resulted in a dose- and time-dependent elevation of stromelysin-1 mRNA levels, the maximum enhancement being up to approximately sevenfold. This effect was abolished by cycloheximide, suggesting a requirement for ongoing protein synthesis. Transient cell transfections with a promoter/reporter gene construct containing 1.3 kb of 5' flanking DNA of the human stromelysin-1 gene linked to the chloramphenicol acetyl transferase (CAT) gene, indicated enhancement of promoter activity by LR. This enhancement was abolished by a single base substitution in the AP-1 binding site of the promoter. Furthermore, gel mobility shift assays demonstrated enhanced AP-1 binding activity in nuclear extracts from cells incubated with LR. However, LR did not alter the activity of a construct containing three AP-1 sequences in front of the thymidine kinase promoter linked to the CAT gene. These results collectively suggest that activation of stromelysin-1 gene expression by LR is mediated by AP-1 regulatory elements which are necessary, but not sufficient, for gene response.