Ovary

Regulated Expression of ADAM8 (a Disintegrin and Metalloprotease 8) in the Mouse Ovary: Evidence for a Regulatory Role of Luteinizing Hormone, Progesterone Receptor, and Epidermal Growth Factor-Like Growth Factors

Abstract
ADAM8 is a disintegrin and metalloprotease family member expressed in immune, neuronal and bone progenitor cells and thought to be involved in tissue remodeling process. Microarray analyses indicated that Adam8 is a potential target of the progesterone receptor (Pgr) in murine ovary. Further studies documented that ADAM8 mRNA and protein are expressed in granulosa cells and cumulus cells of peri-ovulatory follicles whereas expression was significantly reduced in Pgr null mice that fail to ovulate. There was 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 expression in the absence of hCG. In vitro studies with primary mouse granulosa cells documented that Adam8 was 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 1Kb of the mouse Adam8 promoter by PCR and sub-cloned into pGL3-luciferase reporter construct. The Adam8 promoter-luciferase constructs were induced by Fo and PMA treatment after transfection into rat granulosa cells, and co-transfection with a PGR-A expression vector further augmented basal and Fo/PMA inducibility. Site-specific mutations within the -615/+50 promoter documented that a GC rich region, NF-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 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.

Key words: Ovary • Luteinizing hormone • Ovulation • Progesterone receptor