Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110.
Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110.
Proc Natl Acad Sci U S A. 2020 Sep 29;117(39):24403-24414. doi: 10.1073/pnas.2008032117. Epub 2020 Sep 14.
Calcium signals are initiated in immune cells by the process of store-operated calcium entry (SOCE), where receptor activation triggers transient calcium release from the endoplasmic reticulum, followed by opening of plasma-membrane calcium-release activated calcium (CRAC) channels. ORAI1, ORAI2, and ORAI3 are known to comprise the CRAC channel; however, the contributions of individual isoforms to neutrophil function are not well understood. Here, we show that loss of ORAI1 partially decreases calcium influx, while loss of both ORAI1 and ORAI2 completely abolishes SOCE. In other immune-cell types, loss of ORAI2 enhances SOCE. In contrast, we find that ORAI2-deficient neutrophils display decreased calcium influx, which is correlated with measurable differences in the regulation of neutrophil membrane potential via KCa3.1. Decreased SOCE in ORAI1-, ORAI2-, and ORAI1/2-deficient neutrophils impairs multiple neutrophil functions, including phagocytosis, degranulation, leukotriene, and reactive oxygen species (ROS) production, rendering ORAI1/2-deficient mice highly susceptible to staphylococcal infection. This study demonstrates that ORAI1 and ORAI2 are the primary components of the neutrophil CRAC channel and identifies subpopulations of neutrophils where cell-membrane potential functions as a rheostat to modulate the SOCE response. These findings have implications for mechanisms that modulate neutrophil function during infection, acute and chronic inflammatory conditions, and cancer.
钙信号是通过钙库操纵性钙内流（SOCE）过程在免疫细胞中引发的，其中受体激活触发内质网中钙的短暂释放，随后打开质膜钙释放激活钙（CRAC）通道。ORAI1、ORAI2 和 ORAI3 已知构成 CRAC 通道；然而，单个同工型对中性粒细胞功能的贡献尚不清楚。在这里，我们表明 ORAI1 的缺失部分降低了钙内流，而 ORAI1 和 ORAI2 的缺失完全消除了 SOCE。在其他免疫细胞类型中，ORAI2 的缺失增强了 SOCE。相比之下，我们发现 ORAI2 缺陷的中性粒细胞显示出钙内流减少，这与通过 KCa3.1 调节中性粒细胞膜电位的可测量差异相关。ORAI1、ORAI2 和 ORAI1/2 缺陷的中性粒细胞中 SOCE 的减少损害了多种中性粒细胞功能，包括吞噬作用、脱颗粒作用、白三烯和活性氧物质（ROS）的产生，使 ORAI1/2 缺陷的小鼠极易受到葡萄球菌感染。这项研究表明，ORAI1 和 ORAI2 是中性粒细胞 CRAC 通道的主要组成部分，并确定了中性粒细胞亚群，其中细胞膜电位作为变阻器来调节 SOCE 反应。这些发现对调节感染、急性和慢性炎症以及癌症期间中性粒细胞功能的机制具有重要意义。
