Parys J B, McPherson S M, Mathews L, Campbell K P, Longo F J
Howard Hughes Medical Institute, Iowa City, Iowa 52242.
Dev Biol. 1994 Feb;161(2):466-76. doi: 10.1006/dbio.1994.1045.
The presence of inositol 1,4,5-triphosphate receptor (InsP3R), calreticulin, and calsequestrin was demonstrated in eggs of sea urchins (Lytechinus pictus, Lytechinus variegatus, and Strongylocentroutus purpuratus) and Xenopus laevis. Binding of inositol 1,4,5-trisphosphate (InsP3) to microsomes of L. pictus eggs was inhibited by heparin and NaCl. An affinity-purified antibody against the C-terminal of the type I InsP3R, which recognizes InsP3R isoforms of rabbit brain (273 kDa) and Xenopus oocytes and eggs (256 kDa), reacted with a 373-kDa protein in sea urchin eggs. The 373-kDa protein was tentatively identified as the sea urchin egg InsP3R. Observations with fluorescence microscopy indicated that the InsP3R is present throughout the cytoplasm of sea urchin eggs in a pattern consistent with the distribution of endoplasmic reticulum. Small differences in the relative amount of reaction deposits in cortex vs subcortex were noted among the species of sea urchins examined. Reaction product was also localized to the periphery of female pronuclei in eggs of all three sea urchins. InsP3R reactivity was present in the perinuclear region, along the periphery of the germinal vesicle, and throughout the animal and vegetal hemispheres of Xenopus oocytes. A similar cytoplasmic staining pattern was also observed in eggs, although islands of reactivity, much larger than those in oocytes, were present in the animal hemisphere of eggs. Calreticulin and calsequestrin in sea urchin eggs had the same molecular mass as in rabbit brain (56 and 60 kDa, respectively), but differed from those present in Xenopus oocytes/eggs (61 and 57 kDa, respectively). The distribution of calreticulin and calsequestrin in both sea urchin and Xenopus oocytes and eggs was similar to that observed for the InsP3R. These results are discussed in relation to previous studies of Ca2+ regulation during egg development and fertilization and suggest that in the oocytes and eggs of the species examined, InsP3-sensitive Ca2+ stores play an important role in the regulation of cellular Ca2+.
在海胆（花斑疣海胆、多色疣海胆和紫球海胆）和非洲爪蟾的卵中证实了肌醇1,4,5 -三磷酸受体（InsP3R）、钙网蛋白和肌集钙蛋白的存在。肝素和氯化钠可抑制肌醇1,4,5 -三磷酸（InsP3）与花斑疣海胆卵微粒体的结合。一种针对I型InsP3R C末端的亲和纯化抗体，可识别兔脑（273 kDa）以及非洲爪蟾卵母细胞和卵（256 kDa）中的InsP3R亚型，该抗体与海胆卵中的一种373 kDa蛋白质发生反应。暂将该373 kDa蛋白质鉴定为海胆卵InsP3R。荧光显微镜观察表明，InsP3R以与内质网分布一致的模式存在于海胆卵的整个细胞质中。在所检查的海胆物种中，注意到皮质与皮质下反应沉积物的相对量存在微小差异。反应产物也定位于所有三种海胆卵中雌原核的周边。InsP3R反应性存在于非洲爪蟾卵母细胞的核周区域、沿生发泡周边以及整个动物半球和植物半球。在卵中也观察到类似的细胞质染色模式，尽管在卵的动物半球存在比卵母细胞中更大的反应性岛。海胆卵中的钙网蛋白和肌集钙蛋白与兔脑中的分子量相同（分别为56 kDa和60 kDa），但与非洲爪蟾卵母细胞/卵中存在的不同（分别为61 kDa和57 kDa）。海胆和非洲爪蟾卵母细胞及卵中钙网蛋白和肌集钙蛋白的分布与InsP3R的分布相似。结合卵发育和受精过程中Ca2+调节的先前研究对这些结果进行了讨论，结果表明在所研究物种的卵母细胞和卵中，InsP3敏感的Ca2+储存库在细胞Ca2+调节中起重要作用。
