CONSTITUTIVE ACTIVATION OF THE COLLAGENASE PROMOTER IN RECESSIVE DYSTROPHIC EPIDERMOLYSIS-BULLOSA FIBROBLASTS - ROLE OF ENDOGENOUSLY ACTIVATED AP-1

Recessive dystrophic epidermolysis bullosa (RDEB) is a mutilating dise ase of the skin characterized by recurrent blistering and erosions tha t result from compromised integrity of the basement membrane zone. In this study, fibroblasts derived from the skin of RDEB patients were ch aracterized for expression of the major metalloproteinases, particular ly interstitial collagenase. Consistent with previous reports on incre ased collagenase protein levels in fibroblasts from some RDEB patients , we found that steady-state levels of collagenase mRNA were significa ntly increased in fibroblast strains derived from three of five RDEB p atients compared to fibroblasts obtained from normal donors. Stromelys in mRNA was elevated in the same three fibroblast strains, whereas exp ression of neither the 72- nor the 92-kDa type IV collagenases was dif ferent from that of controls. Tissue inhibitor of metalloproteinases w as expressed in RDEB fibroblasts at levels similar to those observed i n normal fibroblasts. To investigate the mechanism behind the steady-s tate elevation in collagenase and stromelysin expression, AP-1 express ion and activation were studied. Although levels of Jun expression wer e not different from those seen in normal fibroblasts, AP-1 activity, as assessed by ability to bind to a TPA response element-containing ol igonucleotide, was endogenously elevated in RDEB fibroblasts compared to normal fibroblasts. Transfection studies using a plasmid construct containing the collagenase promoter linked to a CAT reporter gene demo nstrated that RDEB fibroblasts were able to support active transcripti on of the promoter compared to normal fibroblasts. These studies suppo rt the hypothesis that RDEB fibroblasts contain chronically activated AP-1, and perhaps other transactivating factors, that contribute to th e cellular phenotype of collagenase and stromelysin overexpression. (C ) 1994 Academic Press, Inc.