Puppo A, Chun Jong T, Gragnaniello Giovanni, Garante Ezio, Santella Luigia
Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
PLoS One. 2008;3(10):e3588. doi: 10.1371/journal.pone.0003588. Epub 2008 Oct 30.
When preparing for fertilization, oocytes undergo meiotic maturation during which structural changes occur in the endoplasmic reticulum (ER) that lead to a more efficient calcium response. During meiotic maturation and subsequent fertilization, the actin cytoskeleton also undergoes dramatic restructuring. We have recently observed that rearrangements of the actin cytoskeleton induced by actin-depolymerizing agents, or by actin-binding proteins, strongly modulate intracellular calcium (Ca2+) signals during the maturation process. However, the significance of the dynamic changes in F-actin within the fertilized egg has been largely unclear.
METHODOLOGY/PRINCIPAL FINDINGS: We have measured changes in intracellular Ca2+ signals and F-actin structures during fertilization. We also report the unexpected observation that the conventional antagonist of the InsP(3) receptor, heparin, hyperpolymerizes the cortical actin cytoskeleton in postmeiotic eggs. Using heparin and other pharmacological agents that either hypo- or hyperpolymerize the cortical actin, we demonstrate that nearly all aspects of the fertilization process are profoundly affected by the dynamic restructuring of the egg cortical actin cytoskeleton.
CONCLUSIONS/SIGNIFICANCE: Our findings identify important roles for subplasmalemmal actin fibers in the process of sperm-egg interaction and in the subsequent events related to fertilization: the generation of Ca2+ signals, sperm penetration, cortical granule exocytosis, and the block to polyspermy.
在准备受精时，卵母细胞经历减数分裂成熟过程，在此期间内质网（ER）会发生结构变化，从而导致更有效的钙反应。在减数分裂成熟及随后的受精过程中，肌动蛋白细胞骨架也会发生显著的重组。我们最近观察到，由肌动蛋白解聚剂或肌动蛋白结合蛋白诱导的肌动蛋白细胞骨架重排，在成熟过程中强烈调节细胞内钙（Ca2+）信号。然而，受精卵内F-肌动蛋白动态变化的意义在很大程度上尚不清楚。
方法/主要发现：我们测量了受精过程中细胞内Ca2+信号和F-肌动蛋白结构的变化。我们还报告了一个意外的观察结果，即肌醇三磷酸（InsP(3)）受体的传统拮抗剂肝素，会使减数分裂后卵子中的皮质肌动蛋白细胞骨架过度聚合。使用肝素和其他使皮质肌动蛋白低聚或高聚的药理试剂，我们证明受精过程的几乎所有方面都受到卵子皮质肌动蛋白细胞骨架动态重组的深刻影响。
结论/意义：我们的研究结果确定了质膜下肌动蛋白纤维在精卵相互作用过程以及随后与受精相关的事件中的重要作用：Ca2+信号的产生、精子穿透、皮质颗粒胞吐作用以及多精受精阻断。
