title: Increased expression of ERp57 in rat oocytes during meiotic maturation is associated with sperm-egg fusion.
abstract: Oocyte meiotic maturation is a developmental transition that starts during germinal-vesicle breakdown and ends at the arrest in metaphase of meiosis II. This transition is associated with changes to both the proteins that are synthesized and the abundance/distribution of post-translational modifications that are crucial for subsequent fertilization and embryogenesis. Here, we isolated and cultured rat oocytes in vitro during both metaphase of meiosis I (MI) and meiosis II (MII) stages, respectively, and then compared their proteomic profiles by high-resolution, two-dimensional gel electrophoresis (2DE) followed by mass spectrometry. We found that the expression of five proteins was up-regulated while six proteins were down-regulated when comparing MI to MII oocytes. The expression of ERp57, an endoplasmic reticulum chaperone, underwent a dramatic increase between MI and MII oocytes, and became concentrated in a dome-shaped area of the cell surface within the microvillar region. A similar profile was observed during spermatogenesis, and sperm ERp57 eventually localized to the head and flagellum surfaces, finally ending in the equatorial region of acrosome-reacted sperm. Given the localization pattern, we tested and found that a polyclonal antiserum created against recombinant rat ERp57 significantly inhibited spermatozoa from penetrating zona pellucida-free oocytes without affecting either sperm motility or the acrosome reaction. These results indicate that ERp57 expression on oocytes, and possibly sperm, plays an important physiological role during sperm-egg fusion.
authors.affiliation: Department of Human Anatomy, Histology and Embryology, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.forename: Yemin
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Wu
authors.forename: Yandong
authors.initials: Y
authors.lastname: Li
authors.forename: Qiangsu
authors.initials: Q
authors.lastname: Guo
authors.forename: Weiping
authors.initials: W
authors.lastname: Li
authors.forename: Zhide
authors.initials: Z
authors.lastname: Ding
mesh_terms: D000177:Acrosome / Q000737:chemistry; D000818:Animals; D002478:Cells, Cultured; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D005307:Fertilization in Vitro; D020869:Gene Expression Profiling; D007106:Immune Sera; D008297:Male; D013058:Mass Spectrometry; D008540:Meiosis; D008561:Membrane Fusion; D008871:Microvilli / Q000737:chemistry; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D040901:Proteomics; D051381:Rats; D011994:Recombinant Proteins / Q000276:immunology; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013347:Subcellular Fractions / Q000737:chemistry
chemical_list: D007106:Immune Sera; D011994:Recombinant Proteins; C513196:PDIA3 protein, rat; D019704:Protein Disulfide-Isomerases