Serotonin-dependent collagenase transcription in myometrial cells requiresextended AP-1 site

Primary cultures of uterine smooth muscle cells from post-partum rats expre ss interstitial collagenase in response to serotonin and the serotonin-depe ndent production of interleukin-1 (IL-1) [Wilcox, B.D., Dumin, J.A. and Jef frey, J.J. Serotonin regulation of interleukin-1 messenger RNA in rat uteri ne smooth muscle cells. Relationship to the production of interstitial coll agenase J. Biol. Chem., 269, (1994a), 29658]. Transient transfections of th ese cells indicate that rat collagenase transcription is regulated via a pr oximal consensus AP-1 site within an extended palindrome. Mutation of eithe r the AP-1 site or extended palindrome (EP) decreases promoter activity to approximately 30% of the wild-type. Electrophoretic mobility shift assays r eveal the binding of smooth muscle cell nuclear proteins to the AP-1 EP. Th is binding is barely detectable after mutation of the EP and is completely eliminated by mutation of the AP-1 heptamer. Competition experiments demons trate that binding to the AP-1 EP is specific and of higher affinity than b inding to oligonucleotides containing a mutated EP. Binding to the AP-1 EP is higher when smooth muscle cells are cultured in the presence of serotoni n than in its absence. Although IL-1 is required for collagenase transcript ion, binding to the AP-1 EP appears to be IL-1-independent, FosB, Fra-2, c- Jun, JunB and, most abundantly, JunD bind the AP-1 EP in the absence and pr esence of serotonin. In contrast, Fra-1 expression and binding are serotoni n-dependent suggesting that the activation of Fra-1 may be a key component of collagenase transcriptional activation. (C) 2000 Elsevier Science Irelan d Ltd. All rights reserved.