Department of Physiology and Biophysics, Weill Cornell Medical College in Qatar, Education City, Qatar Foundation, Doha, Qatar.
J Cell Biol. 2010 Nov 1;191(3):523-35. doi: 10.1083/jcb.201006022.
The egg's competency to activate at fertilization and transition to embryogenesis is dependent on its ability to generate a fertilization-specific Ca(2+) transient. To endow the egg with this capacity, Ca(2+) signals remodel during oocyte maturation, including inactivation of the primary Ca(2+) influx pathway store-operated Ca(2+) entry (SOCE). SOCE inactivation is coupled to internalization of the SOCE channel, Orai1. In this study, we show that Orai1 internalizes during meiosis through a caveolin (Cav)- and dynamin-dependent endocytic pathway. Cav binds to Orai1, and we map a Cav consensus-binding site in the Orai1 N terminus, which is required for Orai1 internalization. Furthermore, at rest, Orai1 actively recycles between an endosomal compartment and the cell membrane through a Rho-dependent endocytic pathway. A significant percentage of total Orai1 is intracellular at steady state. Store depletion completely shifts endosomal Orai1 to the cell membrane. These results define vesicular trafficking mechanisms in the oocyte that control Orai1 subcellular localization at steady state, during meiosis, and after store depletion.
卵子在受精时激活并转变为胚胎发生的能力取决于其产生受精特异性 Ca(2+)瞬变的能力。为了赋予卵子这种能力，Ca(2+)信号在卵母细胞成熟过程中重塑，包括储存操作型 Ca(2+)内流（SOCE）的主要 Ca(2+)内流途径失活。SOCE 失活与 SOCE 通道 Orai1 的内化相关。在这项研究中，我们表明 Orai1 在减数分裂过程中通过网格蛋白（Cav）和发动蛋白依赖性的内吞作用途径内化。Cav 与 Orai1 结合，我们在 Orai1 N 端映射出一个 Cav 保守结合位点，该位点是 Orai1 内化所必需的。此外，在静止状态下，Orai1 通过 Rho 依赖性的内吞作用途径在内涵体和细胞膜之间主动循环。在稳定状态下，有相当一部分总 Orai1 存在于细胞内。储存耗尽会将内涵体中的 Orai1 完全转移到细胞膜上。这些结果定义了卵母细胞中的囊泡运输机制，这些机制控制着 Orai1 在稳定状态、减数分裂期间和储存耗尽后的亚细胞定位。
