Protein Kinase C (PKC) Increases TACE/ADAM17 Enzyme Activity in Porcine Ovarian Somatic Cells, Which Is Essential for Granulosa Cell Luteinization and Oocyte Maturation

During in vitro maturation of porcine cumulus cell-oocyte complexes and in vitro luteinization of porcine granulosa cells, FSH induces the expression of the protease TNF alpha-converting enzyme/A disintegrin and metalloproteinase domain 17 (TACE/ADAM17) and the epidermal growth factor (EGF)-like factors, which activate the EGF receptor (EGFR)-MAPK3/1 pathway in both cumulus and granulosa cells. FSH is known to activate not only protein kinase A and p38MAPK pathways in both cell types but also activates protein kinase C (PKC). Because PKC-induced association of cellular-Sarcoma (c-Src) and TACE/ADAM17 is required for TACE/ADAM17 enzyme activation in some cancer cells, we hypothesized that PKC and c-Src impact TACE/ADAM17-mediated activation of EGFR signaling pathway in porcine granulosa and cumulus cells. When granulosa cells or cumulus cell-oocyte complexes were cultured with FSH, PKC activity and c-Src phosphorylation increased and were associated with increased TACE/ADAM17 enzyme activity. The PKC inhibitor calphostin C (CalC) and the c-Src inhibitor (4 amino 5 (4 chlorophenyl) 7 (t butyl) pyrazolo[3,4 d] pyrimidine [PP2]) suppressed TACE/ADAM17 enzyme activity, whereas these inhibitors did not affect Tace/Adam17 mRNA expression. Immunoprecipitation analysis showed that FSH mediated the association of c-Src with TACE/ADAM17 via a PKC-dependent mechanism. Either CalC or PP2 suppressed EGFR downstream signaling pathway (MAPK3/1) in these ovarian cell types and reduced cumulus expansion, meiotic maturation of oocytes, and progesterone production. The negative effects were overcome by the addition of amphiregulin. Collectively, these results indicate that activation of TACE/ADAM17 via a PKC-induced c-Src-dependent manner mediates proteolytic activation of the EGF-like factors that are involved in the induction of granulosa cell differentiation, cumulus expansion, and meiotic maturation of porcine oocytes in vitro.