title: Detection of neurotrophin-4 (NT-4) in ejaculated bull spermatozoa and its effect on spermatozoa mitochondrial activity.
abstract: Recently, we demonstrated that two members of neurotrophins, nerve growth factor and brain-derived neurotrophic factor, and two types of receptor, tyrosine kinase A (TrkA) and tyrosine kinase (TrkB), exist in ejaculated bull spermatozoa, and play a crucial role in the normal function of spermatozoa. Neurotrophin-4 (NT-4) is another neurotrophic factor that signals predominantly through the TrkB receptor tyrosine kinase, and no reports of detection of NT-4 in spermatozoa have been published. In the present study, the presence of NT-4 in mature bull spermatozoa was investigated using RT-PCR, immunofluorescence and Western blotting. The result shows that there was no RT-PCR evidence for NT-4 transcripts in bovine spermatozoa. However, the NT-4 protein was present in bovine spermatozoa, and the NT-4 immunoreactivity was localized to the equatorial segment and midpiece of bovine spermatozoa. In addition, effects of NT-4 on function of spermatozoa were studied. Significant increased mitochondria activity of mature bovine spermatozoa was observed in response to 300 or 500 ng/ml exogenous NT-4 (p < 0.05), in comparison with the control, while addition of inhibitors (40 ng/ml k252α) specific for tyrosine protein kinase significantly blocked the increase of mitochondria activity. However, NT-4 had no effects on the viability or acrosome reaction of spermatozoa (p > 0.05). Consequently, this study provided evidence that NT-4 protein was presented in the mature bull spermatozoa and can influence the mitochondrial activity of bovine spermatozoa through TrkB tyrosine kinase-dependent pathways.
authors.affiliation: Jilin Provincial Key Laboratory of Animal Embryo Engineering, College of Animal Science and Veterinary Medicine, Jilin University, Changchun, Jilin, China.
authors.forename: C-Q
authors.initials: CQ
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: Y-F
authors.initials: YF
authors.lastname: Sun
authors.forename: D
authors.initials: D
authors.lastname: Wang
authors.forename: C-J
authors.initials: CJ
authors.lastname: Li
authors.forename: W-H
authors.initials: WH
authors.lastname: Li
authors.forename: C
authors.initials: C
authors.lastname: Lu
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: H
authors.initials: H
authors.lastname: Wu
authors.forename: X-F
authors.initials: XF
authors.lastname: Hou
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: X
authors.initials: X
authors.lastname: Zhou
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004542:Ejaculation; D005786:Gene Expression Regulation / Q000502:physiology*; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013094:Spermatozoa / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009414:Nerve Growth Factors; D012333:RNA, Messenger; D011505:Protein-Tyrosine Kinases; C073922:neurotrophin 4