title: Baculovirus expressed C-terminal fragment of bonnet monkey (Macaca radiata) zona pellucida glycoprotein-3 inhibits ZP3-mediated induction of acrosomal exocytosis.
abstract: Zona pellucida glycoprotein-3 (ZP3) has been postulated as the primary sperm receptor in various mammalian species including bonnet monkey (Macaca radiata). However, information on the domain responsible for its binding to spermatozoa is inadequate. In the present study, bonnet monkey ZP3 (bmZP3), corresponding to amino acid (aa) residues 223-348 [bmZP3(223-348)] has been cloned and expressed using baculovirus expression system. SDS-PAGE and Western blot analysis of the purified renatured recombinant protein revealed it as a closely spaced doublet of approximately 25 kDa. Lectin-binding studies documented the presence of both O- as well as N-linked glycans. The biotinylated r-bmZP3(223-348) binds to the acrosomal region of the capacitated spermatozoa but fails to bind to the acrosome-reacted spermatozoa as investigated by immunofluorescence studies. In ELISA, nonbiotinylated r-bmZP3(223-348) and baculovirus expressed r-bmZP3, devoid of signal sequence and transmembrane-like domain [r-bmZP3(23-348)] competitively inhibit its binding to the capacitated spermatozoa. Interestingly, binding of biotinylated r-bmZP3(23-348) to the capacitated sperm is also inhibited by nonbiotinylated r-bmZP3(223-348). In contrast to r-bmZP3(23-348), r-bmZP3(223-348) failed to induce acrosomal exocytosis in the capacitated sperm. Interestingly, it competitively inhibits the acrosomal exocytosis induced by r-bmZP3(23-348). These studies, for the first time, identify a domain of ZP3 capable of binding to capacitated spermatozoa and inhibiting ZP3-mediated induction of acrosomal exocytosis furthering our understanding of mammalian fertilization.
authors.affiliation: Gamete Antigen Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
authors.forename: Gagandeep Kaur
authors.initials: GK
authors.lastname: Gahlay
authors.forename: Deepika
authors.initials: D
authors.lastname: Batra
authors.forename: Satish K
authors.initials: SK
authors.lastname: Gupta
mesh_terms: D000177:Acrosome / Q000502:physiology*; D020101:Acrosome Reaction / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D016367:Baculoviridae; D002478:Cells, Cultured; D004527:Egg Proteins / Q000235:genetics / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects* / Q000502:physiology; D005260:Female; D015870:Gene Expression; D008255:Macaca radiata / Q000502:physiology*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000494:pharmacology*; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D000072216:Zona Pellucida Glycoproteins
chemical_list: D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D000072216:Zona Pellucida Glycoproteins