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Signaling through extracellular signal-regulated kinase is required for spermatogonial proliferative response to stem
S Dolci1, M Pellegrini, S Di Agostino
1Dipartimento di Sanitá Pubblica e Biologia Cellulare, Sezione di Anatomia, Universita' degli Studi di Roma Tor Vergata, via O. Raimondo 8, 00173 Rome, Italy.
Abstract:
In vitro addition of stem cell factor (SCF) to c-kit-expressing A(1)-A(4) spermatogonia from prepuberal mice stimulates their progression into the mitotic cell cycle and significantly reduces apoptosis in these cells. SCF addition results in a transient activation of extracellular signal-regulated kinases (Erk)1/2 as well as of phosphatidylinositol 3-kinase (PI3K)-dependent Akt kinase. These events are followed by a rapid re-distribution of cyclin D3, which becomes predominantly nuclear, whereas its total cellular amount does not change. Nuclear accumulation of cyclin D3 is coupled to transient activation of the associated kinase activity, assayed using the retinoblastoma protein (Rb) as a substrate. These events were followed by a transient accumulation of cyclin E, stimulation of the associated histone H1-kinase activity, a delayed accumulation of cyclin A2, and Rb hyper-phosphorylation. All the events associated with SCF-induced cell cycle progression are inhibited by the addition of either a PI3K inhibitor or a mitogen-activated protein-kinase kinase (MEK) inhibitor, indicating that both MEK and PI3K are essential for c-kit-mediated proliferative response. On the contrary, the anti-apoptotic effect of SCF is not influenced by the separate addition of either MEK or PI3K inhibitors. Thus, SCF effects on mitogenesis and survival in c-kit expressing spermatogonia rely on different signal transduction pathways.
Insights
Stem cell factor (SCF) promotes mouse spermatogonia cell cycle progression and reduces apoptosis via distinct signaling pathways. SCF activates kinases, influencing cell cycle proteins and survival, but these effects are differentially regulated.
Area of Science:
- Reproductive Biology
- Cell Signaling
- Molecular Endocrinology
Background:
- Stem cell factor (SCF) and its receptor c-kit play crucial roles in spermatogenesis.
- Understanding the molecular mechanisms of SCF signaling in early spermatogonia is essential for reproductive health research.
Purpose of the Study:
- To investigate the in vitro effects of SCF on c-kit-expressing spermatogonia from prepuberal mice.
- To elucidate the specific signaling pathways involved in SCF-mediated cell cycle progression and apoptosis reduction.
Main Methods:
- Addition of SCF to isolated A(1)-A(4) spermatogonia.
- Analysis of cell cycle progression markers (cyclins, kinase activities) and apoptosis.
- Pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein-kinase kinase (MEK) pathways.
Main Results:
- SCF stimulates spermatogonia into mitosis and reduces apoptosis.
- SCF transiently activates extracellular signal-regulated kinases (Erk)1/2 and PI3K-dependent Akt kinase.
- SCF induces nuclear accumulation and kinase activity of cyclin D3, followed by cyclin E and cyclin A2 accumulation, leading to retinoblastoma protein (Rb) hyper-phosphorylation.
- MEK and PI3K inhibitors block SCF-induced cell cycle progression but not the anti-apoptotic effect.
Conclusions:
- SCF promotes spermatogonia proliferation and survival through distinct signaling pathways.
- MEK and PI3K are essential for SCF-mediated mitogenesis but not for its anti-apoptotic effects.
- SCF signaling in spermatogonia involves differential regulation of cell cycle progression and apoptosis.