Proteomic profiles of buffalo spermatozoa and seminal plasma.

A comprehensive identification of the proteins of spermatozoa and seminal plasma enables the full characterization of sperm biology and is essential to understand how seminal plasma influences sperm fertility. In this study, proteomics of buffalo spermatozoa and seminal plasma were analyzed using a bottom-up approach. A total of 2147 and 864 proteins were identified from mature spermatozoa and seminal plasma, respectively. Of these, 371 proteins-42.9% in the seminal plasma set-were common to both spermatozoa and seminal plasma. ODF2, AKAP4, and TUBB were the most highly abundant proteins of spermatozoa whereas the three most highly abundant proteins in seminal plasma were ALB, CLU, and AZGP1. Gene Ontology (GO) analysis indicated that most sperm proteins were involved in transport, phosphorylation and macromolecule localization. More seminal plasma proteins were related to proteolysis, response to stimulus and homeostatic process. Pathways associated with energy metabolism, protein processing and RNA transport were significantly enriched in spermatozoa. In buffalo seminal plasma, three distinguishing GO pathways-proteasome activity, lysosomal activity, complement and coagulation cascades-were found to play important roles in sperm protection. Protein-protein interaction (PPI) network analysis indicated that 531 and 620 proteins participated in buffalo sperm and seminal plasma PPI networks, respectively. Sub-network mining elaborated detailed biological events. This study is the first to provide an in-depth proteomic analysis of buffalo spermatozoa and seminal plasma. The results extend our understanding of male buffalo reproduction and provide clues for determining the relationships between sperm biology and seminal plasma.