Parathyroid hormone (PTH) plays a central role in regulation of calcium metabolism. Excessive or inappropriate production of PTH or the related protein (PTHrP), accounts for the majority of the causes of hypercalcemia. Both hormones act through the same receptor on the osteoblast to elicit enhanced bone resorption by the osteoclast. Thus, the osteoblast mediated the effect of PTH in the resorption process. In addition to PTH inducing unknown factors which activate the osteoclast, this hormone also stimulates the osteoblast to produce neutral proteinases, such as plasminogen activator and collagenase (matrix metalloproteinase 1, MMP-1) which may be involved in enabling resorption by the osteoclast. We have shown that PTH markedly stimulates secretion of collagenase by the rat osteoblastic cell line, UMR 106-01, and the effects at the protein level are preceded by an 80-fold increase in collagenase mRNA. These effects of PTH are caused by changes in transcription which require continuing protein synthesis. In addition, we have found that the elevated transcription of the MMP-1 gene is preceded by increased in mRNA levels for c-fos and c-jun, two members of the AP-1 (activator protein-1) family of transcription factors. Taken together, we have developed the hypothesis that PTH causes its effects on transcription of the MMP-1 gene by: stimulating transcription of genes for transcription factors whose translations products bind to specific sites in the MMP-1 gene and markedly enhance its transcription. Thus, the aims of the present proposal are to delineate the nature of the cis and trans regulatory elements which control transcription of MMP-1 by the osteoblast in the presence of PTH. This will be done by, 1) ascertaining the minimal PTH regulatory regions in the upstream regulatory region of the rat MMP-1 gene, 2) identifying nuclear proteins which bind to this regulatory element and determining whether these are from the AP-1 family. If this is so, 3) we will determine the necessity for fos in induction of MMP-1 by pTH. If fos is not involved, 4) we will purify and identify and identify the trans-acting factors, and, if these are novel factors, 5) clone the novel factors. The result of this work should aid in establishing the mechanism by which PTH exerts its nuclear effects on osteoblast function. In so doing, the data should also provide some insight and information into the treatment of disorders of calcium metabolism.
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