Ionic regulation of macrophage phenotype and plasticity - all cells rely on transmembrane ION channels to set their resting membrane potential and regulate physiological processes

As the most numerous and ubiquitous class of k+ channel groups, the first family of voltage-gated potassium (KV1) channels regulate physiological functions in various organ systems, but recently, their role in impacting immune cell activity has garnered attention. KV1.3 is the major KV1 isoform in immune cells, including macrophages, where IT influences cytokine production and migration. Although numerous signaling pathways impact KV channels, their interaction with specific intracellular proteins, the KVΒ subunits, are key regulators of channel stability and trafficking. Not only does KVΒ subunit presence influence the activity of KV channels, but KVΒ has been identified as an active aldo-keto reductase (AKR) whose activity directly regulates KV channel gating and subsequent KV-channel mediated potassium efflux (IKV). Additionally, initial reports have demonstrated that KVΒ isoforms are differentially induced in macrophages in vitro depending on the activation stimuli. However, the functional regulation of KV1 channels by KVΒ catalysis which may control macrophage phenotype has yet to be fully elucidated. Our preliminary data suggest that KV1.3 is upregulated with inflammatory stimuli and that its direct pharmacological inhibition disrupts macrophage polarization and acute phagocytotic function. Further, our data indicate a role for KVΒ2 in macrophage pro-resolving functions as genetic deletion of this subunit significantly inhibits macrophage efferocytosis, in vivo. Guided by these findings, we hypothesize that macrophage activation depends on the catalytic regulation of KV1 channels by KVΒ and that binding of specialized pro-resolving lipid mediators (spms) to the active site of KVΒ shifts macrophage phenotype from pro- inflammatory to pro-resolving. To test our hypothesis, we will: (1) determine the extent to which KVΒ subunit expression and enzymatic activity impact macrophage function and phenotype; and (2) elucidate the impact of lipid mediators binding to the KVΒ AKR domain on its enzymatic function and overall macrophage phenotype. Completion of this project will delineate how non-canonical SPM interactions with KVΒ dictate macrophage phenotype through suppression of potassium efflux (IKV) through KV1.3, the major voltage-gated potassium (KV) channel isoform in macrophages. We expect to find that spms binding to KVΒ's AKR domain acts as a central nexus that affords macrophages the ability to complete the phenotypic switch to resolution which must take place for the proper cessation of inflammation. Such knowledge is important because IT could be used to develop more efficacious, targeted strategies to lessen chronic inflammatory challenges while mitigating the potential off-target effects of blocking the entire KV channel pore, due to KV channel ubiquity in most organ systems. Additionally, elucidation of these processes will not only enhance our understanding of mechanisms underlying fundamental macrophage biology, but the findings could also be used to develop new therapeutic avenues to diminish hyper- and chronic inflammatory pathologies.