Rakow T L, Shen S S
Department of Zoology, Iowa State University, Ames 50011.
Proc Natl Acad Sci U S A. 1990 Dec;87(23):9285-9. doi: 10.1073/pnas.87.23.9285.
Fertilization initiates a transient increase in intracellular Ca2+ principally by Ca2+ release from intracellular stores. Possible multiple Ca2+ stores and multiple receptor regulation of the same store have been reported. Here we report the presence of at least two independent intracellular Ca2+ stores in the sea urchin egg, which are released during fertilization. Ca2+ release from one store is mediated by inositol 1,4,5-trisphosphate (IP3) and is sensitive to low molecular weight heparin. The other store is heparin insensitive and independent of IP3 regulation, but the regulatory factor remains unidentified. A transient increase in Ca2+ in heparin-loaded eggs is observed during fertilization, which suggests that IP3-independent Ca2+ release mediates the production of IP3 and release of the IP3-dependent store. Experiments presented here do not support the idea of sperm receptor coupling to inositol phospholipid hydrolysis through a GTP-binding protein mediating the fertilization response.
受精主要通过细胞内钙库释放Ca2+引发细胞内Ca2+的短暂增加。已有报道称可能存在多个钙库，且同一钙库存在多种受体调控方式。在此，我们报告海胆卵中至少存在两个独立的细胞内钙库，它们在受精过程中会被释放。一个钙库的Ca2+释放由肌醇1,4,5 -三磷酸（IP3）介导，且对低分子量肝素敏感。另一个钙库对肝素不敏感，且不受IP3调控，但其调控因子仍未明确。在受精过程中观察到肝素处理过的卵中Ca2+有短暂增加，这表明不依赖IP3的Ca2+释放介导了IP3的产生以及依赖IP3的钙库的释放。本文所呈现的实验不支持精子受体通过介导受精反应的GTP结合蛋白与肌醇磷脂水解偶联的观点。
