Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli I-80121, Italy.
Biochem Biophys Res Commun. 2013 Nov 15;441(2):301-7. doi: 10.1016/j.bbrc.2013.09.103. Epub 2013 Oct 5.
Being present in starfish oocytes, the cofilin/ADF (actin-depolymerizing factor) family protein depactin severs actin filaments. Previously, we reported that exogenous cofilin microinjected into starfish eggs significantly augmented the Ca(2+) release in response to inositol 1,4,5-trisphosphate (InsP3) or fertilizing sperm, raising the possibility that intracellular Ca(2+) signaling could be modulated by the actin cytoskeleton. In this communication, we have targeted the endogenous depactin by use of the specific antibody that was raised against its actin-binding domain. The anti-depactin antibody microinjected into the starfish oocytes and eggs effectively altered the structure of the actin cytoskeleton, and significantly delayed the meiotic progression induced by 1-methyladenine. When microinjected into the mature eggs, the anti-depactin antibody markedly reduced the amplitude of the Ca(2+) response in a dose-dependent manner, corroborating the results of our previous study with cofilin. In addition, the eggs microinjected with the anti-depactin antibody displayed reduced rate of successful elevation of the fertilization envelope and an elevated tendency of polyspermic interaction. Taken together, our data suggest that the actin cytoskeleton is implicated not only in meiotic maturation and intracellular Ca(2+) signaling, but also in the fine regulation of gametes interaction and cortical granules exocytosis.
在海星卵母细胞中存在着丝切蛋白/ADF（肌动蛋白解聚因子）家族蛋白 depactin，它可以切断肌动蛋白丝。此前，我们曾报道过，外源的丝切蛋白被微注射到海星卵中，可显著增强卵对肌醇 1,4,5-三磷酸（InsP3）或受精精子的钙释放反应，这表明细胞内钙信号可能受到肌动蛋白细胞骨架的调节。在本研究中，我们利用针对其肌动蛋白结合结构域的特异性抗体来靶向内源性的 depactin。该抗 depactin 抗体被微注射到海星卵母细胞和卵中，有效地改变了肌动蛋白细胞骨架的结构，并显著延迟了 1-甲基腺嘌呤诱导的减数分裂进程。当将该抗体微注射到成熟卵中时，其以剂量依赖的方式显著降低了 Ca(2+)反应的幅度，这与我们之前用丝切蛋白进行的研究结果一致。此外，该抗体微注射的卵显示出受精囊升高的成功率降低，并且多精受精的趋势升高。总之，我们的数据表明，肌动蛋白细胞骨架不仅参与减数分裂成熟和细胞内 Ca(2+)信号转导，还参与配子相互作用和皮质颗粒胞吐的精细调节。
