Characterization of carp seminal plasma proteome in relation to blood plasma

The present study for the first time characterizes a diverse cohort of carp seminal and blood plasma proteins using the combination of protein fractionation by one-dimensional gel electrophoresis and high performance liquid chromatography electrospray ionization tandem mass spectrometry. Using this approach, we identified 137 proteins in carp seminal plasma and 88 proteins in carp blood plasma, most of which were newly identified in fish. Transferrin, serine proteinase inhibitors, apolipoproteins, complement C3 and Wap65 were present in high abundance in carp seminal plasma. In carp blood plasma, besides these proteins, immunoglobulins and macroglobulins were identified as major proteins. Comparative analysis of carp seminal and blood plasma proteome performed using 2D-DIGE revealed that in contrast to mammals the majority (1014 from 1240 spots) of carp seminal plasma proteins are blood proteins. Moreover, proteins more abundant in seminal plasma (99 from 1240 spots) were identified, including parvalbumin, isoforms of apolipoproteins, heat shock proteins, components of antioxidative system, matrix metalloproteinases, cathepsin D, enzymes of glycolysis and sperm structural proteins. These proteins are involved in the regulation of sperm motility, spermatogenesis, maintenance of sperm membrane lipid stability and antioxidant protection. This study enhances the basic knowledge concerning fish seminal plasma protein composition and their potential role in fish reproduction.

Proteins similar or identical to blood plasma components are important for male reproductive physiology. Comparative study of blood and seminal plasma is especially justified in fish. Using 2D-DIGE we indicated that, in contrast to mammals, in carp seminal plasma most proteins are common for blood and seminal plasma, which possibly is related to a lack of accessory glands in reproductive tract of most fish. The proteins present in higher abundance in seminal plasma can be related to physiology of fish male reproduction including regulation of sperm motility, spermatogenesis, maintenance of sperm surface composition and antioxidant protection. Application of proteomics analysis to identify carp seminal and blood plasma proteins significantly extends current knowledge regarding the composition of fish seminal and blood plasma proteins and their relationship to higher vertebrates. Moreover, proteomic profiling of carp seminal plasma appears to be helpful for further understanding of the role of fish seminal plasma proteins in male reproductive tract as well as for identification of novel biomarkers for sperm quality.