title: Analysis of recombinant human semenogelin as an inhibitor of human sperm motility.
abstract: Eppin (epididymal protease inhibitor [SPINLW1]) is present in a protein complex on the human sperm surface that contains lactotransferrin, clusterin, and semenogelin (SEMG1). During ejaculation the presence of semenogelin inhibits sperm progressive motility until semenogelin is hydrolyzed by prostate-specific antigen (PSA). Although eppin binds all three components in its protein complex, the binding of semenogelin to eppin appears to be critical for the inhibition of progressive motility. The effect of the originally identified seminal plasma motility inhibitor fragment has not been clearly defined on live spermatozoa. Therefore, we have used recombinant semenogelin (rSEMG1) and its fragments, including a semenogelin mutant in which cysteine 239 was changed to glycine, coupled with a computer assisted sperm analysis assay to study the motility inhibitory properties of semenogelin. Each fragment and the mutant were tested for their effects on motility. Recombinant semenogelin significantly inhibited sperm progressive motility in a dose- and time-dependent manner. The C-terminal semenogelin fragment (amino acids 164-283) containing cysteine 239 significantly inhibited sperm progressive motility, whereas the N-terminal fragment (amino acids 24-163), a short C-terminal fragment (amino acids 172-215) without cysteine 239, and the mutant fragment (amino acids 24-283 with glycine 239) did not inhibit motility. After treatment with recombinant semenogelin, spermatozoa could be washed and treated with PSA, partially reversing the inhibition of progressive motility. Cysteine 239 of rSEMG1 appears to be the critical amino acid for both binding to eppin and inhibiting sperm motility.
authors.affiliation: Department of Cell and Developmental Biology and Laboratories for Reproductive Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
authors.forename: Anurag
authors.initials: A
authors.lastname: Mitra
authors.forename: Richard T
authors.initials: RT
authors.lastname: Richardson
authors.forename: Michael G
authors.initials: MG
authors.lastname: O'Rand
mesh_terms: D001665:Binding Sites / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D008297:Male; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D053491:Proteinase Inhibitory Proteins, Secretory / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D029607:Seminal Vesicle Secretory Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D013081:Sperm Motility / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D013997:Time Factors
chemical_list: C431553:Eppin protein, human; D053491:Proteinase Inhibitory Proteins, Secretory; D011994:Recombinant Proteins; D029607:Seminal Vesicle Secretory Proteins; C424482:seminal vesicle-specific antigen