Role of MAPK and PKC signaling pathways in the regulation of c-erbB₂ in the primordial follicles onset / 生理学报

ABSTRACT

Our previous studies showed that the proto-oncogene c-erbB₂ played an important role in primordial follicles growth. The present study was conducted to investigate the role of MAPK and PKC signaling pathways in the primordial follicle onset in neonatal rats, and the relationship between c-erbB₂ and MAPK/PKC signaling pathways. Ovaries collected from 2-day-old Sprague-Dawley rats were cultured in the Waymouth culture system in vitro. Ovaries were transfected with c-erbB₂ siRNA, or treated with PD98059 (50 mumol/L) or Calphostin (0.5 mumol/L) in the culture medium. RT-PCR was performed to measure the expression of c-erbB₂ mRNA, and Western blot analysis was performed to measure the expression of ErbB₂, MAPK and PKC protein after the neonatal rat ovaries were cultured for 8 d. The quantities of every-stage follicles of ovaries cultured for 8 d were obtained in histological section stained with hematoxylin eosin. The results showed that c-erbB₂ siRNA reduced the levels of c-erbB₂ mRNA (P<0.01) and the levels of ErbB₂, MAPK and PKC protein (P<0.01) significantly. But the levels of c-erbB₂ mRNA and ErbB₂ protein exhibited no change (P>0.05) in the ovaries cultured with PD98059 or Calphostin. After the ovaries were transfected with c-erbB₂ siRNA or cultured with PD98059 or Calphostin for 8 d, the quantities of primary follicles and second follicles were lower than those in the control group (P<0.05 or P<0.01), but the quantity of the primordial follicles was higher than that in the control group (P<0.01). These results suggest that proto-oncogene c-erbB₂ promotes the initiation of primordial follicle growth through the MAPK and PKC signal transduction, and c-erbB₂ is possibly the upstream of PKC and MAPK signaling pathway in the regulation of primordial follicle onset.