Parys J B, Sernett S W, DeLisle S, Snyder P M, Welsh M J, Campbell K P
Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City 52242.
J Biol Chem. 1992 Sep 15;267(26):18776-82.
Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) induces Ca2+ oscillations and waves in Xenopus laevis oocytes. Microsomes from oocytes exhibit high-affinity binding for Ins(1,4,5)P3, and demonstrate Ins(1,4,5)P3-induced Ca2+ release. The Ins(1,4,5)P3 receptor (InsP3R) was purified from oocyte microsomes as a large tetrameric complex and shown to have a monomer molecular mass of 256 kDa, compared with 273 kDa for the brain InsP3R. Binding to the oocyte receptor is highly specific for Ins(1,4,5)P3 and is inhibited by heparin (IC50, 2 micrograms/ml). Immunoblot analysis revealed that an antibody against the C-terminal sequence of the brain receptor recognized the oocyte receptor. These results, in addition to the difference in pattern obtained after limited proteolysis, suggest that the oocyte InsP3R is a new shorter isoform of the mammalian brain type I InsP3R. Immunofluorescence experiments indicated the presence of the InsP3R in the cortical layer and the perinuclear endoplasmic reticulum of the oocyte. However, immunological and biochemical experiments did not reveal the presence of the ryanodine receptor. The presence of an InsP3R and the absence of a ryanodine receptor support the importance of Ins(1,4,5)P3 in Ca2+ handling by oocytes and particularly in the induction of Ca2+ oscillations and waves.
肌醇1,4,5 - 三磷酸（Ins(1,4,5)P3）可诱导非洲爪蟾卵母细胞产生Ca2+振荡和波动。卵母细胞的微粒体对Ins(1,4,5)P3表现出高亲和力结合，并证明了Ins(1,4,5)P3诱导的Ca2+释放。Ins(1,4,5)P3受体（InsP3R）从卵母细胞微粒体中纯化出来，为一种大型四聚体复合物，其单体分子量为256 kDa，而脑InsP3R的单体分子量为273 kDa。与卵母细胞受体的结合对Ins(1,4,5)P3具有高度特异性，并被肝素抑制（IC50，2微克/毫升）。免疫印迹分析表明，针对脑受体C末端序列的抗体可识别卵母细胞受体。这些结果，除了有限蛋白酶解后获得的模式差异外，表明卵母细胞InsP3R是哺乳动物脑I型InsP3R的一种新的较短同工型。免疫荧光实验表明InsP3R存在于卵母细胞的皮质层和核周内质网中。然而，免疫和生化实验未揭示兰尼碱受体的存在。InsP3R的存在和兰尼碱受体的缺失支持了Ins(1,4,5)P3在卵母细胞Ca2+处理中，特别是在Ca2+振荡和波动诱导中的重要性。
