Is stallion epididymal fluid phosphoproteome affected by the equine reproductive season?

This study examines whether the reproductive season impacts the phosphoprotein components of stallion epididymal fluid, affecting sperm maturation. The research uncovers various phosphoproteins serving different functions in the epididymal fluid and observes how their profiles change during and outside the breeding season.

Research Objectives

• The primary goal of this research was to identify and isolate phosphoproteins from the epididymal environment extracted from reproductively mature stallions during and outside the breeding season.

Methodologies

• The study employed 1D-PAGE and nanoLC-MS/MS technologies to identify the various phosphoproteins. They also marked tyrosine, serine, and threonine phosphorylation patterns, keeping in mind the seasonal and epididymal segment variables.
• The intensity of phosphorylation and phosphoprotein profiles were observed to change across different regions of the epididymis.
• Immunoblot and western blot tests were used to ascertain that fourteen proteins experienced phosphorylation during both on and off-breeding seasons.

Findings

• The study found that different phosphoproteins—responsible for regulatory, transport, motility, ubiquitination, chaperone, antioxidant, apoptotic, and enzymatic functions—exhibited various phosphorylation patterns based on the season and the segment of the epididymis.
• Significant differences in the phosphorylation status were observed specifically in the case of various proteins including glutamine synthetase, malate dehydrogenase, clusterin/inorganic pyrophosphatase, clusterin/ubiquitin thioesterase, 14-3-3 protein/purine nucleotide phosphorylase due to the season factor, and Rab GDP dissociation inhibitor alpha, clusterin/ubiquitin thioesterase proteins due to the segment factor.
• Other phosphoproteins were found to appear spontaneously between individuals and across both seasons without significant differences.