Proteomic analysis of seminal extracellular vesicle proteins involved in asthenozoospermia by iTRAQ

Asthenozoospermia is a common cause of male infertility, but in most cases its etiology is unknown. The exocytic cell vesicles called seminal extracellular vesicles in the human seminal fluid have been reported to play a pivotal role in promoting the motility of spermatozoa, and functional disorder of seminal extracellular vesicles may cause male infertility. To determine whether abnormal seminal extracellular vesicles are involved in asthenozoospermia, the differential abundance proteins between normozoospermic (NSEV) and asthenozoospermic seminal extracellular vesicles (ASEV) samples were analyzed by iTRAQ coupled with two-dimensional liquid chromatography-tandem mass spectrometry. A total of 3,699 proteins were identified in the seminal extracellular vesicles (false discovery rate <0.01). Overall, 11 proteins were significantly upregulated (>1.2) in ASEV and 80 were significantly downregulated (<0.833). Functional bioinformatic analysis showed that these proteins with differential abundance were mainly associated with transport, metabolism, and signal pathways. The changes of OPTN, SMYD2, EIF2B2, TRPV6, ACE, PRSS8, and PPAP2A in ASEV were verified by western blot analysis, and we found that the abundance of TRPV6 markedly reduced in the seminal extracellular vesicles and ejaculated spermatozoa of asthenozoospermic patients, which indicated trpv6 was important in sperm motility. This study provides deeper insight into the involvement of seminal extracellular vesicles in asthenozoospermia and should aid the search for novel biomarkers of male infertility.