Quantitative Proteomic Analysis of Seminal Plasma, Sperm Membrane Proteins, and Seminal Extracellular Vesicles Suggests Vesicular Mechanisms Aid in the Removal and Addition of Proteins to the Ram Sperm Membrane

Abstract

Quantitative proteomic studies are contributing greatly to the understanding of the spermatozoon through the provision of detailed information on the proteins spermatozoa acquire and shed in the acquisition of fertility. Extracellular vesicles (EVs) are thought to aid in the delivery of proteins to spermatozoa in the male reproductive tract. The aim of this study is to isolate, identify and quantify EV proteins isolated from ram seminal plasma. Ram sperm plasma membrane proteins are also isolated using nitrogen cavitation and identified to better understand the interplay of proteins between the sperm membrane and extracellular environment. The categorization of proteins enriched in the EV population according to their function revealed three main groupings: vesicle biogenesis, metabolism, and membrane adhesion and remodeling. The latter group contains many reproduction‐specific proteins that show demonstrable links to sperm fertility. Many of these membrane‐bound proteins show testicular expression and are shed from the sperm surface during epididymal maturation (e.g., testis expressed 101; TEX101 and lymphocyte Antigen 6 Family Member K; LY6K). Their association with seminal EVs suggests that EVs may not only deliver protein cargo to spermatozoa but also assist in the removal of proteins from the sperm membrane.

Aldose Reductase B1 in Pig Seminal Plasma: Identification, Localization in Reproductive Tissues, and Relationship With Quality and Sperm Preservation

“…In this regard, all these functions could be driven by both the soluble form of the protein in SP or by that contained in extracellular vesicles (EVs). SP EVs regulate sperm function through its integration to sperm membrane ( Leahy et al, 2020 ) and their action on the female immune system ( Zhang et al, 2020 ). Interestingly, bovine AKR1B1 has been reported to be associated to epididymal EVs ( Frenette et al, 2006 ) and, in humans, seminal EVs have been found to contain aldose reductase ( Zhang et al, 2020 ).…”

Exosome Composition and Seminal Plasma Proteome: A Promising Source of Biomarkers of Male Infertility

“…Along the reproductive tracts, a major breakthrough in exosome research has been the deep characterization of exosomal cargo—by means of the advancement of RNA sequencing and high resolution mass spectrometry methodologies—that is rich in messenger RNAs (mRNAs), non-coding RNAs (ncRNAs) and proteins [ 1 ]. Considering that SPZ are transcriptionally quiescent cells, the acquisition of new secretory products during the post-testicular maturation along the epididymis—ascribed to exosomes of epididymal origin, known as epididymosomes—confers to SPZ a new molecular guise [ 12 , 17 , 18 , 19 , 20 ]. However, sperm travel still continues in female reproductive tracts, where the exosomes play an important role through the activation of inflammatory and immune mechanisms [ 21 ].…”

HDL mediates reverse cholesterol transport from ram spermatozoa and induces hyperactivated motility

“…The specific cholesterol transporters are thus still to be determined in ram spermatozoa. In this light, a recent analysis of the ram sperm plasma membrane proteome is of interest as it reported on the presence of the transporters, ABCA3 and ABCA3L [ 58 ]. Given the structural homology between transporters of the ABC A-subfamily and the reported function in lipid (as well as cholesterol) transport [ 59–61 ], it is well possible these transporters may function in cholesterol efflux from ram sperm to cholesterol acceptors, like HDLs.…”