Heavy metal ions exchange driven protein phosphorylation cascade functions in genomic instability in spermatocytes...

Area of Science:

• Reproductive Biology
• Molecular Toxicology
• Genetics

Background:

• DNA double-strand breaks (DSBs) are critical in spermatocytes, impacting genomic stability and male fertility.
• Cadmium (Cd) is a heavy metal known to cause DNA damage in spermatocytes via poorly understood mechanisms.

Purpose of the Study:

• To elucidate the mechanism by which cadmium induces DNA damage in spermatocytes.
• To investigate the role of DNA repair pathways and protein phosphorylation in cadmium-induced male infertility.

Main Methods:

• Investigated the effect of cadmium ions on non-homologous end-joining (NHEJ) and homologous recombination (HR) DNA repair pathways.
• Analyzed the phosphorylation status of DNA-PKcs at DSB sites.
• Examined the interaction between cadmium, manganese ions, and PP5 phosphatase activity.
• Utilized a mouse model to assess cadmium-induced genomic instability and reproductive dysfunction, and the effect of manganese treatment.

Main Results:

• Cadmium impaired the NHEJ pathway by promoting DNA-PKcs phosphorylation at Ser2056 and Thr2059, causing its dissociation from DNA ends.
• Homologous recombination (HR) pathway remained unaffected by cadmium.
• Cadmium-induced loss of PP5 phosphatase activity, due to dissociation from manganese (Mn) ions, initiated the DNA-PKcs hyper-phosphorylation cascade.
• In vivo, cadmium exposure led to genomic instability and male reproductive dysfunction, which were reversed by high-dose manganese treatment.

Conclusions:

• Cadmium disrupts spermatocyte DNA repair through a protein phosphorylation-mediated pathway, triggered by competitive binding with essential ions like manganese.
• This mechanism contributes to cadmium-induced genomic instability and male infertility.
• Manganese ions show potential as a therapeutic agent to counteract cadmium's reproductive toxicity.