Proteome Profiling of Canine Epididymal Fluid: In Search of Protein Markers of Epididymal Sperm Motility

Sperm maturation in the epididymis is based on interactions with proteins from epididymal fluid (EF). The aim of the study was to profile canine EF proteome and investigate correlations between EF protein content and epididymal spermatozoa (ES) motion parameters. Twenty-three male dogs were divided into two groups: good sperm motility (GSM) and poor sperm motility (PSM). The total motility and progressive motility differed significantly (p = 0.031; p < 0.001, respectively) between the GSM group and the PSM group. The semen samples were centrifuged to separate the EF apart from the ES. The canine EF proteins were analyzed using nano-liquid chromatography, which was coupled with quadrupole time-of-flight mass spectrometry (NanoUPLC-Q-TOF/MS) and bioinformatic tools for the first time. A total of 915 proteins were identified (GSM-506; PSM-409, respectively). UniProt identification resulted in six unique proteins (UPs) in the GSM group of dogs and four UPs in the PSM group. A semi-quantitative analysis showed a higher abundance (p < 0.05) of four differentially expressed proteins in the GSM group (ALB, CRISP2, LCNL1, PTGDS). Motility-dependent variations were detected in the EF proteome and were related to important metabolic pathways, which might suggest that several proteins could be potential ES motility biomarkers.

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

Phosphorylation and dephosphorylation of proteins are considered to be the most important processes in sperm maturation during epididymal transit. The main aim of this study was to isolate and identify phosphoproteins from the epididymal milieu obtained from reproductively mature stallions during and out of the breeding season. With the use of 1D-PAGE and nanoLC-MS/MS, we identified phosphoproteins that fulfil various functions: regulatory, transport, motility, ubiquitination, chaperone, antioxidant, apoptotic and enzymatic. Moreover, we characterized tyrosine, serine and threonine phosphorylation patterns, taking into consideration the seasonal and epididymal segment variables. The intensity of phosphorylation and profiles of phosphoproteins varied in subsequent regions of the epididymis. With the use of western and immunoblot tests, we demonstrated that fourteen proteins underwent phosphorylation both during and out of the breeding season. However, significant differences (p≤0.05) in the phosphorylation status were demonstrated in the case of 44 kDa (glutamine synthetase), 38 kDa (malate dehydrogenase), 34 kDa (clusterin/inorganic pyrophosphatase), 31 kDa (clusterin/ /ubiquitin thioesterase), 29 kDa (14-3-3 protein/purine nucleotide phosphorylase) for the season factor and 55 (Rab GDP dissociation inhibitor alpha) and 31 kDa ((clusterin/ubiquitin thioesterase) proteins for the segment factor. The occurrence of the other phosphoproteins was spontaneous among individuals and in both seasons.