Kir2.1 channels drive macrophage migration through enhancing store-operated Ca entry.

Kir2.1 is an inwardly rectifying K channel that is essential for the generation and regulation of the resting membrane potential in many types of cells such as cardiac myocytes. It is known that Kir2.1 is also expressed in macrophages, but its role in macrophage function remains unclear. In this study, we aimed to reveal the significance of Kir2.1 in bone marrow-derived macrophages (BMDMs) using siRNA and selective inhibitors that target Kir2.1. Inwardly rectifying K currents were consistently observed in mouse BMDMs, and were suppressed by Kir2.1 knockdown or superfusion with BaCl (Ba). Inhibition of Kir2.1 depolarized the resting membrane potential of BMDMs, and this primary response reduced both the resting cytosolic Ca concentration ([Ca]) and store-operated Ca entry. Furthermore, inhibition of Kir2.1 by Ba or siRNA and/or inhibition of Ca release-activated Ca (CRAC) channels by YM58483 attenuated the increase in [Ca] that was induced by the endogenous agonist ATP. Importantly, inhibition of Kir2.1 by Ba or ML133 had no effect on differentiation of bone marrow progenitors to macrophages, M2 polarization, phagocytic activity, or cell proliferation. On the other hand, the inhibition of Kir2.1, CRAC channel, Ca/calmodulin-dependent kinase (CaMK), CaMK kinase (CaMKK), or Pyk2 suppressed BMDM migration. ATP stimulation promoted BMDM migration, but this effect was attenuated by the inhibition of Kir2.1, CRAC channels, and CaMK. These results suggest that Kir2.1 can hyperpolarize the membrane potential of macrophages, increasing Ca influx through CRAC channels and activating CaMK and Pyk2, thereby increasing macrophage motility. In bone marrow-derived macrophages, Kir2.1 regulates the resting membrane potential and can enhance Ca influx through Ca release-activated Ca (CRAC) channels after Ca store depletion or ATP stimulation. Changes in Kir2.1-mediated K currents have minimal effects on macrophage differentiation, M2 polarization, phagocytosis, and proliferation. In contrast, Kir2.1 promoted migration by promoting Ca influx through CRAC channels and subsequent CaMK and Pyk2 activation. Thus, Kir2.1 can control macrophage motility by modulating membrane potential and intracellular Ca signaling.