Ovary

Actions of EGFR/MAPK and Protein Kinase C Signaling in Granulosa Cells from Gallus gallus Are Dependent upon Stage of Differentiation

Abstract
Studies in both mammalian and non-mammalian ovarian model systems have demonstrated that activation of the mitogen activated protein kinase (MAPK) and protein kinase C (PKC) signaling pathways modulates steroid biosynthesis during follicle development, yet the collective evidence for facilitory versus inhibitory roles of these pathways is inconsistent. The present studies in the hen ovary describe the changing role of MAPK and PKC signaling in the regulation of steroidogenic acute regulatory protein (STAR) expression and progesterone production in undifferentiated granulosa cells collected from prehierarchal follicles prior to follicle selection versus differentiated granulosa from preovulatory follicles subsequent to selection. Treatment of undifferentiated granulosa cells with a selective EGFR and ERBB4 receptor tyrosine kinase inhibitor (AG1478) augments both FSH receptor (Fshr) mRNA expression and initiates progesterone production. Conversely, selective inhibitors of both receptor and MAPK activity attenuate steroidogenesis in differentiated granulosa cells subsequent to follicle selection. In addition, inhibition of PKC signaling with GF109203X augments FSH-induced Fshr mRNA plus STAR protein expression and initiates progesterone synthesis in undifferentiated granulosa cells, but inhibits both gonadotropin-induced STAR expression and progesterone production in differentiated granulosa. Granulosa cells from the most recently selected (9-12 mm) follicle represent a stage of transition as inhibition of MAPK signaling promotes, while inhibition of PKC signaling blocks, gonadotropin-induced progesterone production. Collectively, these data describe stage-of-development-related changes in cell signaling whereby the differentiation-inhibiting actions of MAPK and PKC signaling in prehierarchal follicle granulosa cells undergo a transition at the time of follicle selection to become obligatory for gonadotropin-stimulated progesterone production in differentiated granulosa from preovulatory follicles.

Key words: Ovary • Follicle • Granulosa cells • Progesterone • Signal transducers

This article has been cited by other articles:

				A. L. Johnson, M. J. Haugen, and D. C. Woods Role for Inhibitor of Differentiation/Deoxyribonucleic Acid-Binding (Id) Proteins in Granulosa Cell Differentiation Endocrinology, June 1, 2008; 149(6): 3187 - 3195. [Abstract] [Full Text] [PDF]