Proteomic analysis of seminal plasma from locally-adapted “Curraleiro Pé-Duro bulls” (Bos taurus): identifying biomarkers involved in sperm physiology in endangered animals for conservation of biodiversity

The present study was aimed at evaluating the seminal plasma proteins and sperm parameters of Curraleiro Pé-Duro bulls. Semen was collected from 10 bulls by electroejaculation, and sperm parameters were evaluated in fresh and frozen-thawed semen. Seminal plasma proteins were analyzed by 2-D SDS-PAGE and mass spectrophotometry. Tools in computational biology were used to generate bioinformatic knowledge and evaluate gene ontology, protein–protein interactions, phylogenetic trees and multiple sequence alignments. Sperm motility in fresh and frozen-thawed semen was 78.8±1.8% and 21.2±1.6%, respectively. Pearson’s correlations were evaluated (p<0.05). Sperm motility and vigor in fresh semen were correlated with clusterin, TIMP2 and cathepsin S (r=0.64–0.71) and sperm defects were related to inhibitor of carbonic anhydrase and BSP 5 (r=0.78–0.80). Clusterin, BSP 5, alpha-enolase, creatine kinase M-type, glyceraldehyde-3-phosphate dehydrogenase, BSP 3, albumin, and 5′-nucleotidase and legumain were correlated with acrosome intact live sperm (r=0.80–0.64). Associations were detected between sperm vigor and spermadhesin 1 (r=−0.89), and between sperm defects in fresh semen and spermadhesin 1 and clusterin (r=−0.81). Sperm motility in frozen-thawed semen was associated with BSP 1, spermadhesin 1, clusterin and spermadhesin Z13 (r=0.64–0.85). The percent of motile sperm after freeze-thawing was negatively correlated (r=−0.64) with the amount of spermadhesin 1 in the seminal plasma. Based on in silico analysis, TIMP2 interacted with BSP1, BSP3, BSP5 and metalloproteinases. Molecular functions of proteins associated with sperm parameters were binding, catalytic activity and enzymatic regulation. Amino acid sequences of spermadhesin 1 and BSP 1 from Bos taurus, and other domestic species were similar. Phylogenetic tree analysis demonstrated that clusterin from Bos taurus was related to Ovis aries and domains of clusterin, spermadhesin 1, BSP 1 and inhibitor of carbonic anhydrase were conserved as well. In summary, specific seminal proteins are associated with sperm parameters of locally-adapted bulls. Use of the endangered mammalian as a model may assist in understanding aspects of evolutionary adaptations and could improve assisted reproductive biotechnologies.