Journal Article

ORAI1 and ORAI2 modulate murine neutrophil calcium signaling, cellular activation, and host defense

McBride, Helen J., Johnson, Ryan, Pashos, Madeline, Cummings, Celeste, Sampedro, Georgia R., Tycksen, Eric, Lowell, Clifford A., Clemens, Regina A., Kang, Chen, Sah, Rajan, Grimes, Derayvia

2020

Overview

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.

• Publisher: National Academy of Sciences
• Subject: Animals / Biological Sciences / Calcium / Calcium (reticular) / Calcium - immunology / Calcium channels / Calcium influx / Calcium Signaling / Calcium signalling / Cell activation / Chronic infection / Correlation analysis / Degranulation / Endoplasmic reticulum / Female / Immune system / Immunology and Inflammation / Inflammation / Intermediate-Conductance Calcium-Activated Potassium Channels - genetics / Intermediate-Conductance Calcium-Activated Potassium Channels - immunology / Isoforms / Leukocytes (neutrophilic) / Male / Membrane potential / Membranes / Mice / Mice, Inbred C57BL / Neutrophils / Neutrophils - immunology / Orai1 protein / ORAI1 Protein - genetics / ORAI1 Protein - immunology / ORAI2 Protein - genetics / ORAI2 Protein - immunology / Phagocytosis / Reactive oxygen species / Receptor mechanisms / Signal processing / Subpopulations