Regulated expression of ADAM8 (a disintegrin and metalloprotease domain 8) in the mouse ovary: evidence for a regulatory role of luteinizing hormone, progesterone receptor, and epidermal growth factor-like growth factors.

ADAM8 (a disintegrin and metalloprotease domain 8) is expressed in immune, neuronal, and bone progenitor cells and is thought to be involved in the tissue-remodeling process. Microarray analyses indicate that Adam8 is a potential target of the progesterone receptor (Pgr) in murine ovary. Further studies document that Adam8 mRNA and protein are expressed in granulosa cells and cumulus cells of periovulatory follicles whereas expression is significantly reduced in Pgr null mice that fail to ovulate. There is a reduced expression in granulosa cells from cultured, in vitro ovulated follicles exposed to inhibitors of progesterone or epidermal growth factor signaling while epiregulin induced its expression in the absence of hCG. In vitro studies with primary mouse granulosa cells document that Adam8 is induced in response to forskolin (Fo) and phorbol ester (PMA) or Fo and Amphiregulin treatment. To understand the transcriptional regulation of the Adam8, we amplified 1 kb of the mouse Adam8 promoter by PCR and subcloned it into a pGL3-luciferase reporter construct. The Adam8 promoter-luciferase constructs are induced by Fo and PMA treatment after transfection into rat granulosa cells, and cotransfection with a PGR-A expression vector further augment basal and Fo/PMA inducibility. Site-specific mutations within the -615/+50 promoter document that a GC-rich region, NF-1 (nuclear factor-1) site, and putative TATA box are critical for Adam8 promoter activation by Fo/PMA. Thus, ADAM8 is expressed in a stage-specific manner and is hormonally regulated in ovulating follicles by the coordinate actions of LH and PGR. To our knowledge, ADAM8 is the first member of the ADAM family shown to be hormonally regulated.