Shirakawa Hideki, Ito Masahiko, Sato Moritoshi, Umezawa Yoshio, Miyazaki Shunichi
Department of Applied Physics and Chemistry, The University of Electro-Communications, Tokyo 182-8585, Japan.
Biochem Biophys Res Commun. 2006 Jun 30;345(2):781-8. doi: 10.1016/j.bbrc.2006.04.133. Epub 2006 May 2.
Intracellular Ca2+ oscillations in fertilized mammalian eggs, the key signal that stimulates egg activation and early embryonic development, are regulated by inositol 1,4,5-trisphosphate (IP3) signaling pathway. We investigated temporal changes in intracellular IP3 concentration ([IP3]i) in mouse eggs, using a fluorescent probe based on fluorescence resonance energy transfer between two green fluorescent protein variants, during Ca2+ oscillations induced by fertilization or expression of phospholipase Czeta (PLCzeta), an egg-activating sperm factor candidate. Fluorescence measurements suggested the elevation of [IP3]i in fertilized eggs, and the enhancement of PLCzeta-mediated IP3 production by cytoplasmic Ca2+ was observed during Ca2+ oscillations or in response to CaCl2 microinjection. The results supported the view that PLCzeta is the sperm factor to stimulate IP3 pathway, and suggested that high Ca2+ sensitivity of PLCzeta activity and positive feedback from released Ca2+ are important for triggering and maintaining Ca2+ oscillations.
受精哺乳动物卵中的细胞内钙离子振荡是刺激卵激活和早期胚胎发育的关键信号，由肌醇1,4,5-三磷酸（IP3）信号通路调控。我们使用基于两个绿色荧光蛋白变体之间荧光共振能量转移的荧光探针，研究了在受精或卵激活精子因子候选物磷脂酶Cζ（PLCζ）表达诱导的钙离子振荡过程中，小鼠卵中细胞内IP3浓度（[IP3]i）的时间变化。荧光测量表明受精卵中[IP3]i升高，并且在钙离子振荡期间或响应氯化钙显微注射时，观察到细胞质钙离子增强了PLCζ介导的IP3产生。结果支持了PLCζ是刺激IP3途径的精子因子这一观点，并表明PLCζ活性的高钙离子敏感性以及释放的钙离子的正反馈对于触发和维持钙离子振荡很重要。
