Calcium Signaling via Orai1 Is Essential for Induction of the Nuclear Orphan Receptor Pathway To Drive Th17 Differentiation

Abstract

Orai1 is the pore subunit of Ca2+ release-activated Ca2+ (CRAC) channels that stimulate downstream signaling pathways crucial for T cell activation. CRAC channels are an attractive therapeutic target for alleviation of autoimmune diseases. Using high throughput chemical library screening targeting Orai1, we identified a novel class of small molecules that inhibit CRAC channel activity. One of these molecules, compound 5D inhibited CRAC channel activity by blocking ion permeation. When included during differentiation, TH17 cells showed higher sensitivity to compound 5D than TH1 and TH2 cells. The selectivity was attributable to high dependence of promoters of retinoic-acid-receptor-related orphan receptors on Ca2+-nuclear-factor-of-activated-T cells (NFAT) pathway. Blocking of CRAC channels drastically decreased recruitment of NFAT and histone modifications within key gene loci involved in TH17 differentiation. The impairment in TH17 differentiation by treatment with CRAC channel blocker was recapitulated in Orai1-deficient T cells, which could be rescued by exogenous expression of retinoic-acid-receptor-related orphan receptors or a constitutive active mutant of NFAT. In vivo administration of CRAC channel blockers effectively reduced the severity of experimental autoimmune encephalomyelitis by suppression of differentiation of inflammatory T cells. These results suggest that CRAC channel blockers can be considered as chemical templates for development of therapeutic agents to suppress inflammatory responses.

Selective ORAI1 Inhibition Ameliorates Autoimmune Central Nervous System Inflammation by Suppressing Effector but Not Regulatory T Cell Function

“…Inhibition of Kv1.3 depolarizes the plasma membrane and reduces the electrical gradient required for Ca 2+ influx through CRAC channels in T cells (40). More recently, Gwack and colleagues identified inhibitors of CRAC channels that prevented the development of EAE in mice when administered at the time of EAE induction (41). We show here, for the first time to our knowledge, that inhibition of CRAC channels during established EAE ameliorates CNS inflammation and disease severity.…”

“…A recent study showed decreased expression of the Th17-specific transcription factors RORα and RORγt in Th17 cells from Orai1 −/− mice (41). By contrast, we did not observe reduced mRNA and protein expression of Rorc in Th17 cells and Tbx21 in Th1 cells derived from Orai1 fl/fl Cd4-Cre mice.…”

“…Given the similar degree of EAE attenuation in mice with genetic deletion of Orai1 in T cells and WT mice treated with AMG1, the main effects of the inhibitor on EAE are likely to result from inhibition of encephalitogenic T cells. Similar to AMG1, another CRAC channel inhibitor that was recently reported suppressed Th17 cell function and differentiation without affecting iTreg differentiation (41). A less toxic derivative of that compound was able to prevent EAE when administered before onset of the disease; its therapeutic effect on established EAE was not tested.…”

Localized Store-Operated Calcium Influx Represses CD95-Dependent Apoptotic Effects of Rituximab in Non-Hodgkin B Lymphomas

“…To date, intense drug discovery efforts have focused on developing small-molecule CRAC-channel antagonists (40)(41)(42) or specific Orai1 Abs (43) to treat autoimmune diseases and chronic inflammation. We propose using these compounds in association with RTX or, more generally, with drugs inducing a CD95-dependent apoptotic pathway, to constitute a new therapeutic opportunity for patients.…”

A novel analytical brain block tool to enable functional annotation of discriminatory transcript biomarkers among discrete regions of the fronto-limbic circuit in primate brain

“…These signaling ligands regulate expression of the Alzheimer Disease related amyloid precursor protein (APP), analogous with HOMER3 (#7). Retinoic acid signaling in hippocampus is itself driven by calcium signaling (Kim et al, 2014), and regulates 4 genes: LMO1 (#6) (Rice et al, 2004); TTR (#3) (Brouillette and Quirion, 2008); AQP3 (#9) (Song et al, 2008); and shares regulation of Netrin G2 (#10) (Korecka et al, 2013) with the calcium signaling mechanism.…”