The endothelial nitric oxide synthase/cyclic guanosine monophosphate/protein kinase G pathway activates primordial follicles

Aging (Albany NY). 2020 Dec 3;13(1):1096-1119. doi: 10.18632/aging.202235. Epub 2020 Dec 3.


In mammals, the well-organized activation of quiescent primordial follicles is pivotal for female reproductive reserve. In the present study, we examined the mechanisms underlying primordial follicle activation in mice. We found that endothelial nitric oxide synthase (eNOS) and its downstream effectors, cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase G (PKG), were expressed in pre-granulosa cells and promoted primordial follicle activation, oocyte growth and granulosa cell proliferation in neonatal ovaries. Mammalian target of rapamycin (mTOR) colocalized with PKG in pre-granulosa cells and was essential for eNOS/cGMP/PKG pathway-induced primordial follicle activation. The eNOS/cGMP/PKG pathway was found to stabilize mTOR protein. The mRNA levels of F-box and WD repeat domain containing 7 (FBXW7), an E3 ubiquitin ligase, correlated negatively with mTOR protein levels in neonatal ovaries. FBXW7 bound to and destabilized mTOR protein in pre-granulosa cells in a ubiquitin/proteasome-dependent manner. However, agonists of the eNOS/cGMP/PKG pathway reduced FBXW7 mRNA levels. FBXW7 overexpression suppressed primordial follicle activation and prevented the eNOS/cGMP/PKG pathway from activating primordial follicles and stabilizing mTOR protein. These findings demonstrate that the eNOS/cGMP/PKG pathway activates primordial follicles by suppressing FBXW7-induced ubiquitination of mTOR in mice.

Keywords: FBXW7; eNOS/cGMP/PKG pathway; mTOR; primordial follicle activation; ubiquitination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Cell Proliferation
  • Cyclic GMP / metabolism*
  • Cyclic GMP-Dependent Protein Kinase Type I / metabolism*
  • F-Box-WD Repeat-Containing Protein 7 / metabolism
  • Female
  • Forkhead Box Protein O3 / metabolism
  • Granulosa Cells / metabolism*
  • Mice
  • Nitric Oxide Synthase Type III / metabolism*
  • Oocytes / growth & development
  • Oocytes / metabolism*
  • Organ Culture Techniques
  • Ovarian Follicle / growth & development
  • Ovarian Follicle / metabolism*
  • Ovary / metabolism*
  • Protein Transport
  • TOR Serine-Threonine Kinases / metabolism
  • Ubiquitination


  • F-Box-WD Repeat-Containing Protein 7
  • Fbxw7 protein, mouse
  • Forkhead Box Protein O3
  • FoxO3 protein, mouse
  • Nitric Oxide Synthase Type III
  • Nos3 protein, mouse
  • mTOR protein, mouse
  • TOR Serine-Threonine Kinases
  • Cyclic GMP-Dependent Protein Kinase Type I
  • Prkg1 protein, mouse
  • Cyclic GMP