The mechanism underlying PAK1-mediated regulation of estrogen secretion in Bactrian camels' granulosa cells via the steroid pathway.

Abstract

This study investigates the regulatory role of p21-activated protein kinase 1 (PAK1) in estrogen secretion during ovulation induction in Bactrian camels, along with the associated molecular mechanisms. We evaluated the morphological differences of follicles between ovulatory and non-ovulatory camels through rectal examinations and B-ultrasound imaging. Using iTRAQ quantitative proteomics, we identified a significant upregulation of PAK1 protein in the ovarian tissues of the ovulatory group, followed by a bioinformatics analysis to explore its biological functions. Our results revealed distinct tissue-specific expression and distribution patterns of PAK1 within the hypothalamic-pituitary-gonadal (HPG) axis. In in vitro cultured ovarian granulosa cells, FTY720-induced activation of PAK1 significantly increased cell viability, reduced apoptosis rates, and decreased the expression of apoptosis-related molecules. Additionally, PAK1 activation enhanced the expression of key enzymes and receptors involved in estrogen synthesis, promoting estradiol secretion. Conversely, inhibiting PAK1 with IPA-3 resulted in opposing effects, exacerbating granulosa cell apoptosis and reducing estrogen synthesis. Overall, this study demonstrates that PAK1 is essential for regulating estrogen secretion by modulating granulosa cell apoptosis and the expression of key steroidogenic enzymes, ultimately influencing ovulation induction in Bactrian camels. These findings improve our understanding of the reproductive regulatory mechanisms in camels and provide a molecular framework for further investigations into ovulation induction and enhancements in reproductive performance.