Apoptosis signal-regulating kinase (ASK1) and transcription factor tumor suppressor protein TP53 suppress rabbit ovarian granulosa cell functions

This study was conducted with the aim to understand the roles of apoptosis signal-regulating kinase (ASK1) and transcription factor tumor suppressor protein TP53, as well as the possible interrelationships, in the control of healthy ovarian cell functions. Rabbit ovarian granulosa cells were transfected with constructs encoding ASK1, TP53, or TP53 + ASK1 and cultured with or without insulin-like growth factor 1 (IGF1). The accumulation of ASK1, the cytoplasmic apoptosis regulators SAX and BCL2, and proliferating cell nuclear antigen (PCNA, a cell proliferation marker), as well as progesterone release, were evaluated by quantitative immunocytochemistry and radioimmunoassay. Results indicate both ASK1 and TP53 promoted the accumulation of BAX, but suppressed that of BCL2 and PCNA. Progesterone release was inhibited by ASK1 and promoted by TP53, while TP53 also stimulated ASK1 accumulation. Additionally, IGF1 stimulated PCNA and reduced progesterone release, but did not affect ASK1. Transfection with ASK1, TP53, or TP53 + ASK1 could modify IGF1 activity, however, there was no cumulative effect with co-transfection of TP53 and ASK1. This is the first results that indicate there is ASK1 suppression of healthy ovarian granulosa cell functions, including promoting apoptosis, inhibiting proliferation, and alter progesterone release. There was also TP53 actions in rabbit ovarian granulosa cells, where it stimulated ASK1, apoptosis, and progesterone release, thus suppressing proliferation and responses to IGF1. The similarity of ASK1 and TP53 effects on apoptosis and proliferation, lack of cumulative action of these molecules, and capacity of TP53 to promote ASK1 accumulation suggest that TP53 can suppress some ovarian granulosa cell functions through ASK1 stimulation.