Influence of the Season and Region Factor on Phosphoproteome of Stallion Epididymal Sperm

Simple Summary Phosphorylation and dephosphorylation of proteins are considered to be the most important processes in sperm maturation during the epididymal transit. We demonstrated that 27 proteins underwent phosphorylation both in and out of the breeding season. Differences in the phosphorylation status were demonstrated in the case of endoplasmic reticulum chaperone BiP, albumin, protein disulfide-isomerase A3, nesprin-1, peroxiredoxin-5, and protein bicaudal D homolog. Epididymal maturation can be defined as a scope of changes occurring during epididymal transit that prepare spermatozoa to undergo capacitation. One of the most common post-translational modifications involved in the sperm maturation process and their ability to fertilise an oocyte is the phosphorylation of sperm proteins. The aim of this study was to compare tyrosine, serine, and threonine phosphorylation patterns of sperm proteins isolated from three subsequent segments of the stallion epididymis, during and out of the breeding season. Intensities of phosphorylation signals and phosphoproteins profiles varied in consecutive regions of the epididymis. However, significant differences in the phosphorylation status were demonstrated in case of endoplasmic reticulum chaperone BiP (75 and 32 kDa), protein disulfide-isomerase A3 (50 kDa), nesprin-1 (23 kDa), peroxiredoxin-5 (17 kDa), and protein bicaudal D homolog (15 kDa) for season x type of phosphorylated residues variables. Significant differences in the phosphorylation status were also demonstrated in case of endoplasmic reticulum chaperone BiP and albumin (61 kDa), protein disulfide-isomerase A3 (50 kDa), and protein bicaudal D homolog (15 kDa) for region x type of phosphorylated residues variables.