PPP6R3-mediated dephosphorylation regulates mRNA translation during spermatogonial differentiation

Area of Science:

• Reproductive Biology
• Molecular Cell Biology
• Biochemistry

Background:

• Protein dephosphorylation by phosphatases plays a role in spermatogenesis.
• The specific substrates and regulatory mechanisms of phosphatases in spermatogenesis remain largely unknown.

Purpose of the Study:

• To investigate the role of protein phosphatase 6 regulatory subunit 3 (PPP6R3) in spermatogenesis.
• To identify the substrates and molecular mechanisms by which PPP6R3 regulates male germ cell differentiation.

Main Methods:

• Germline-specific knockout mouse model (Ppp6r3-cKO) was generated.
• Immunoprecipitation and Western blotting were used to detect protein interactions and phosphorylation levels.
• Overexpression of mutant eukaryotic initiation factors (EIF3C, EIF4G1) in cell culture.

Main Results:

• Germline deletion of PPP6R3 caused abnormal spermatogonial differentiation and male infertility.
• PPP6R3 deletion led to increased phosphorylation and degradation of EIF3C and EIF4G1, inhibiting translation.
• Overexpression of non-phosphorylatable mutants of EIF3C and EIF4G1 rescued the differentiation defect.

Conclusions:

• PPP6R3, as part of the PP6 holoenzyme, directly interacts with and dephosphorylates EIF3C and EIF4G1.
• Dephosphorylation of EIF3C and EIF4G1 by PPP6R3 is essential for activating translation of mRNAs required for spermatogonial differentiation.
• PPP6R3-mediated regulation of translation is critical for male fertility.