title: Correlation of epididymal protease inhibitor and fibronectin in human semen.
abstract: OBJECTIVE
  Epididymal protease inhibitor (Eppin) was located on the surface of spermatozoa and modulates the liquefaction of human semen. Here, we identify the correlative protein partner of Eppin to explore the molecular mechanism of liquefaction of human semen.
  
  
  METHODS
  (1) Human seminal vesicle proteins were transferred on the membrane by Western blotting and separated by 2-D electrophoresis and incubated in recombinant Eppin. The correlative protein was identified by Mass Spectrometry (MS) (2). Western blotting was used to determine the relation of rEppin and rFibronectin(Fn); (3) Co-localization in spermatozoa were detected using immunofluorescence; (4) Correalation of Eppin and Fn was proved by co-immunoprecipitation.
  
  
  RESULTS
  Fn was identified as the binding partner of recombinant Eppin by MS. Recombinant of Eppin was made and demonstrated that the Eppin fragment binds the fn 607-1265 fragment. The Eppin-Fn complex presents on the sperm tail and particularly in the midpiece region of human ejaculated spermatozoa. Immunoprecipitation indicated that Eppin in the spermatozoa lysates was complexed with Fn.
  
  
  CONCLUSIONS
  Our study demonstrates that Eppin and Fn bind to each other in human semen and on human ejaculated spermatozoa. Eppin-Fn complex may involve in semen coagulation, liquefaction and the survival and preparation of spermatozoa for fertility in the female reproductive tract.
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China ; Department of Urology, Jiangsu Provice Official Hospital, Nanjing, China.
authors.forename: Xiangxiang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Jianzheng
authors.initials: J
authors.lastname: Fang
authors.affiliation: Department of Urology, Affiliated Zhongda Hospital of Southeast University, Dingjiaqiao, Nanjing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Shengli
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Shifeng
authors.initials: S
authors.lastname: Su
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Song
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Hainan
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Niu
authors.affiliation: State Key Laboratory of Reproductive Medicine, Department of Urology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Zengjun
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004822:Epididymis / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011485:Protein Binding; D053491:Proteinase Inhibitory Proteins, Secretory / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012661:Semen / Q000737:chemistry / Q000378:metabolism*; D055101:Semen Analysis; D029607:Seminal Vesicle Secretory Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C431553:Eppin protein, human; D005353:Fibronectins; D053491:Proteinase Inhibitory Proteins, Secretory; D029607:Seminal Vesicle Secretory Proteins