title: Phosphorylation of inositol 1,4,5-triphosphate receptor 1 during in vitro maturation of porcine oocytes.
abstract: During fertilization in mammalian species, a sperm-induced intracellular Ca(2+) signal ([Ca(2+)](i)) mediates both exit of meiosis and oocyte activation. Recently, we demonstrated in mouse oocytes that the phosphorylation levels of inositol 1,4,5 trisphosphate receptor type1 (IP(3)R1), the channel responsible for Ca(2+) release and oscillations during fertilization, changed during maturation and fertilization. Therefore, we examined the expression and phosphorylation of IP(3)R1 during in vitro maturation of pig oocytes. Here, our present study shows that expression of IP(3)R1 protein did not change during maturation, although the phosphorylation status of the receptor, specifically at an MPM-2 epitope, did. We found that while at the beginning of maturation IP(3)R1 lacked MPM-2 immunoreactivity, it became MPM-2 reactive by 24 h and reached maximal reactivity by 36 h. Interestingly, the acquisition of MPM-2 reactivity coincided with the activation of p34(cdc2) kinase and mitogen-activated protein kinase (MAPK), which are involved in meiotic progression. Following completion of maturation, inactivation of MAPK by U0126 did not affect IP(3)R1 phosphorylation, although inactivation of p34(cdc2) kinase by roscovitine dramatically reduced IP(3)R1 phosphorylation. Neither inhibitor affected total expression of IP(3)R1. Altogether, our results show that IP(3)R1 undergoes dynamic phosphorylation during maturation and this might underlie the generation of oscillations at fertilization.
authors.affiliation: Laboratory of Animal Reproduction, School of Veterinary Medicine, Azabu University, Sagamihara, Japan. itoj@azabu-u.ac.jp
authors.forename: Junya
authors.initials: J
authors.lastname: Ito
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yoshida
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kasai
authors.forename: Takuya
authors.initials: T
authors.lastname: Wakai
authors.forename: Jan B
authors.initials: JB
authors.lastname: Parys
authors.forename: Rafael A
authors.initials: RA
authors.lastname: Fissore
authors.forename: Naomi
authors.initials: N
authors.lastname: Kashiwazaki
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D000939:Epitopes / Q000378:metabolism; D005260:Female; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D008540:Meiosis / Q000502:physiology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D034421:Sus scrofa
chemical_list: D000939:Epitopes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D010750:Phosphoproteins; D016203:CDC2 Protein Kinase; D020928:Mitogen-Activated Protein Kinases