Increased Confinement and Polydispersity of STIM1 and Orai1 after Ca2+ Store Depletion
Increased Confinement and Polydispersity of STIM1 and Orai1 after Ca2+ Store Depletion
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Ca2 储存耗尽后 STIM1 和 Orai1 的限制和多分散性增加
DOI：
10.1016/j.bpj.2019.11.019
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发表时间：
2020-01-07
影响因子：
3.4
通讯作者：
Park, Hyokeun
中科院分区：
文献类型：
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作者：
Qin, Xianan;Liu, Lei;Park, Hyokeun
STIM1（内质网 (ER) 膜中的 Ca2+ 传感器）和 Orai1（质膜中 Ca2+ 释放激活的钙通道的成孔亚基）分别在内质网膜和质膜中扩散。当 ER 中的 Ca2+ 储存耗尽时，STIM1 易位至 ER-质膜连接处并结合 Orai1 以触发储存操作的 Ca2+ 进入。然而，人们对 STIM1 和 Orai1 在此过程中的运动及其对 Ca2+ 进入的作用知之甚少。在这里，我们报告了 Ca2+ 储存耗尽前后活细胞内质网和质膜中单个 STIM1 和 Orai1 颗粒的实时跟踪。我们发现单个 STIM1 和 Orai1 粒子的运动在存储耗尽之前和之后都表现出异常扩散，并且它们的移动性（通过轨迹回转半径、均方位移和广义扩散系数来衡量）在存储耗尽后急剧下降。我们还发现测量的位移分布是非高斯分布的，并且非高斯参数在存储耗尽后急剧增加。详细的分析和模拟表明，在储备耗尽之前和之后，单个 STIM1 和 Orai1 颗粒都被限制在区室膜中，储备耗尽后运动的变化可以通过在内质网 - 质膜连接处形成的 STIM1-Orai1 复合物的限制和多分散性增加来解释。进一步的模拟表明，储存耗尽后限制性和多分散性的增加导致局部 Ca2+ 流入的快速增加，这可以促进局部 Ca2+ 信号通路的快速激活，并在储存操纵的 Ca2+ 进入中有效补充内质网中的 Ca2+ 储存。
STIM1 (a Ca2+ sensor in the endoplasmic reticulum (ER) membrane) and Orai1 (a pore-forming subunit of the Ca2+-release-activated calcium channel in the plasma membrane) diffuse in the ER membrane and plasma membrane, respectively. Upon depletion of Ca2+ stores in the ER, STIM1 translocates to the ER-plasma membrane junction and binds Orai1 to trigger store-operated Ca2+ entry. However, the motion of STIM1 and Orai1 during this process and its roles to Ca2+ entry is poorly understood. Here, we report real-time tracking of single STIM1 and Orai1 particles in the ER membrane and plasma membrane in living cells before and after Ca2+ store depletion. We found that the motion of single STIM1 and Orai1 particles exhibits anomalous diffusion both before and after store depletion, and their mobility-measured by the radius of gyration of the trajectories, mean-square displacement, and generalized diffusion coefficient-decreases drastically after store depletion. We also found that the measured displacement distribution is non-Gaussian, and the non-Gaussian parameter drastically increases after store depletion. Detailed analyses and simulations revealed that single STIM1 and Orai1 particles are confined in the compartmentalized membrane both before and after store depletion, and the changes in the motion after store depletion are explained by increased confinement and polydispersity of STIM1-Orai1 complexes formed at the ER-plasma membrane junctions. Further simulations showed that this increase in the confinement and polydispersity after store depletion localizes a rapid increase of Ca2+ influx, which can facilitate the rapid activation of local Ca2+ signaling pathways and the efficient replenishing of Ca2+ store in the ER in store-operated Ca2+ entry.