EPPIN is a sperm-surface drug target for male contraception. Here we investigated EPPIN-interacting proteins in mouse spermatozoa. We showed that EPPIN is an androgen-dependent gene, expressed in the testis and epididymis, but also present in the vas deferens, seminal vesicle and adrenal gland. Mature spermatozoa presented EPPIN staining on the head and flagellum. Immunoprecipitation of EPPIN from spermatozoa pre-incubated with seminal vesicle fluid (SVF) followed by LC-MS/MS or Western blot revealed the co-immunoprecipitation of SVS2, SVS3A, SVS5 and SVS6. In silico and Far-Western blot approaches demonstrated that EPPIN binds SVS2 in a protein network with other SVS proteins. Immunofluorescence using spermatozoa pre-incubated with SVF or recombinant SVS2 demonstrated the co-localization of EPPIN and SVS2 both on sperm head and flagellum. Our data show that EPPIN's roles in sperm function are conserved between mouse and human, demonstrating that the mouse is a suitable experimental model for translational studies on EPPIN.

中文翻译：

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附睾蛋白酶抑制剂（EPPIN）是小鼠精子中精囊分泌蛋白SVS2结合的蛋白中心。

EPPIN是男性避孕的精子表面药物靶标。在这里，我们研究了小鼠精子中与EPPIN相互作用的蛋白质。我们表明，EPPIN是一种雄激素依赖性基因，在睾丸和附睾中表达，但在输精管，精囊和肾上腺中也存在。成熟的精子在头部和鞭毛上呈EPPIN染色。用精囊液（SVF）预温育的精子中EPPIN的免疫沉淀，然后进行LC-MS / MS或Western印迹显示SVS2，SVS3A，SVS5和SVS6的免疫共沉淀。电子和远西印迹方法证明，EPPIN与其他SVS蛋白质在蛋白质网络中结合SVS2。使用与SVF或重组SVS2预温育的精子进行的免疫荧光显示，EPPIN和SVS2在精子头和鞭毛上均共定位。