Involvement of Inhibitory Nuclear Factor-κB (NFκB)-Independent NFκB Activation in the Gonadotropic Regulation of X-Linked Inhibitor of Apoptosis Expression during Ovarian Follicular Development in Vitro.

Increased X-linked inhibitor of apoptosis (XIAP) expression and suppressed follicular apoptosis are important determinants in the regulation of follicular development by FSH. The objective of the present study was to examine the role and regulation of nuclear factorB (NF B) in the gonadotropic control of granulosa cell XIAP expression and follicular growth in vitro. FSH (100 ng/ml) increased rat granulosa cell XIAP mRNA abundance and protein content. The gonadotropin also induced granulosa cell p65 subunit-containing NF B translocation from cytoplasm to nucleus and increased NF BDNA binding activity. Supershift EMSA indicated the FSHactivated NF B contained p65 and p50 subunits. Unlike TNF , FSH failed to elicit a significant change in granulosa cell phosphoand total-inhibitory NF B (I B) I B contents in vitro and dominant-negative I B expression was ineffective in blocking the increase in NF B-DNA-binding activity and XIAP protein content induced by the gonadotropin. In contrast, SN50 (a cell permeable inhibitory peptide of NF B translocation, 50–200 ng/ml) suppressed FSH-stimulated NF B-DNA binding, XIAP expression, and follicular growth. FSH also increased granulosa cell phospho-Akt contents, a response sensitive to the PI-3K inhibitor LY294002 (10 M). In conclusion, the present studies demonstrate that the FSH-induced XIAP expression is mediated through the NF B pathway through activation of phosphatidylinositol 3-kinase rather than the classical I B kinase. (Endocrinology 143: 2732–2740, 2002)