ROLE OF PROTEIN-KINASE-A IN COLLAGENASE-1 GENE-REGULATION BY PROSTAGLANDIN-E1 - STUDIES IN A RABBIT SYNOVIOCYTE CELL-LINE, HIG-82

Gene expression of the matrix-degrading enzyme collagenase-1 in rabbit synoviocytes and human fibroblasts is down-regulated by prostaglandin E(1) (PGE(1)) through a cyclic adenosine monophosphate (cAMP)-depende nt pathway. In the current study, we examined the role of protein kina se A (PKA) in the PGE(1)-mediated effect on collagenase-1 gene express ion, Collagenase-1 gene expression was rapidly induced several-fold ab ove control both by a phorbol ester, 12-o-tetradecanoyl phorbol 13 ace tate, and interleukin-1 beta (IL-1 beta) in HIG-82 synoviocytes, Treat ment with PGE(1) and forskolin increased PKA activity in the HIG-82 ce lls within 15 minutes of adding the stimulating agents, Two inhibitors of PKA, the isoquinoline-sulfonamide derivative, H-89 and a cAMP anal og, RpcAMP, blocked the ability of PGE(1) to down-regulate collagenase -1 gene expression, However, if PGE, was added from 6 h to 30 minutes before the PKA inhibitor H-89, collagenase-1 gene expression was inhib ited, Constitutive PKA activity was increased in HIG-82 synoviocytes s tably transfected with an expression vector pCMV.C alpha that caused t he HIG-82 cells to overexpress an active catalytic subunit of PKA. Cel ls stably transfected with an inactive, mutated C-alpha-variant showed no change in PKA activity, Collagenase-1 mRNA levels in TPA-stimulate d cells were reduced to baseline levels in the pCMV.C alpha but not in the mutated C-alpha-transfected cells, These data show the importance of PKA in regulating collagenase-1 gene expression in a synoviocyte c ell line.