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Multiple sclerosis (MS) is a chronic inflammatory, likely autoimmune disease of the central nervous system with a combination of genetic and environmental risk factors, among which Epstein-Barr virus (EBV) infection is a strong suspect. We have previously identified increased autoantibody levels toward the chloride-channel protein Anoctamin 2 (ANO2) in MS. Here, IgG antibody reactivity toward ANO2 and EBV nuclear antigen 1 (EBNA1) was measured using bead-based multiplex serology in plasma samples from 8,746 MS cases and 7,228 controls. We detected increased anti-ANO2 antibody levels in MS (P = 3.5 × 10−36) with 14.6% of cases and 7.8% of controls being ANO2 seropositive (odds ratio [OR] = 1.6; 95% confidence intervals [95%CI]: 1.5 to 1.8). The MS risk increase in ANO2-seropositive individuals was dramatic when also exposed to 3 known risk factors for MS: HLA-DRB1*15:01 carriage, absence of HLA-A*02:01, and high anti-EBNA1 antibody levels (OR = 24.9; 95%CI: 17.9 to 34.8). Reciprocal blocking experiments with ANO2 and EBNA1 peptides demonstrated antibody cross-reactivity, mapping to ANO2 [aa 140 to 149] and EBNA1 [aa 431 to 440]. HLA gene region was associated with anti-ANO2 antibody levels and HLA-DRB1*04:01 haplotype was negatively associated with ANO2 seropositivity (OR = 0.6; 95%CI: 0.5 to 0.7). Anti-ANO2 antibody levels were not increased in patients from 3 other inflammatory disease cohorts. The HLA influence and the fact that specific IgG production usually needs T cell help provides indirect evidence for a T cell ANO2 autoreactivity in MS. We propose a hypothesis where immune reactivity toward EBNA1 through molecular mimicry with ANO2 contributes to the etiopathogenesis of MS.

Volume-regulated anion channel (VRAC) is ubiquitously expressed and plays a pivotal role in vertebrate cell volume regulation. A heterologous complex of leucine-rich repeat containing 8A (LRRC8A) and LRRC8B-E constitutes the VRAC, which is involved in various processes such as cell proliferation, migration, differentiation, intercellular communication, and apoptosis. However, the lack of a potent and selective inhibitor of VRAC limits VRAC-related physiological and pathophysiological studies, and most previous VRAC inhibitors strongly blocked the calcium-activated chloride channel, anoctamin 1 (ANO1). In the present study, we performed a cell-based screening for the identification of potent and selective VRAC inhibitors. Screening of 55,000 drug-like small-molecules and subsequent chemical modification revealed 3,3′-((2-hydroxy-3-methoxyphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (VI-116), a novel potent inhibitor of VRAC. VI-116 fully inhibited VRAC-mediated I− quenching with an IC50 of 1.27 ± 0.18 μM in LN215 cells and potently blocked endogenous VRAC activity in PC3, HT29 and HeLa cells in a dose-dependent manner. Notably, VI-116 had no effect on intracellular calcium signaling up to 10 μM, which completely inhibited VRAC, and showed high selectivity for VRAC compared to ANO1 and ANO2. However, DCPIB, a VRAC inhibitor, significantly affected ATP-induced increases in intracellular calcium levels and Eact-induced ANO1 activation. In addition, VI-116 showed minimal effect on hERG K+ channel activity up to 10 μM. These results indicate that VI-116 is a potent and selective VRAC inhibitor and a useful research tool for pharmacological dissection of VRAC.

A strong association between multiple sclerosis (MS) and Epstein-Barr virus (EBV) has been established but the exact role of EBV in MS remains controversial. Recently, molecular mimicry between EBNA1 and specific GlialCAM, CRYAB and ANO2 peptides has been suggested as a possible pathophysiological mechanism. The aim of this study was to analyse anti-EBV antibodies in MS patients against (I) EBV lifecycle proteins, (II) putative cross-reactive peptides, and (III) during treatment. In this retrospective cross-sectional study, 258 serum samples were included consisting of EBV-negative (n = 25) and EBV-positive (n = 36) controls, 192 MS samples including untreated relapsing-remitting MS (RRMS) with and without relapses, secondary progressive MS (SPMS) and primary progressive MS (PPMS) patients, and 106 patients on 8 different treatment regimens. IgG and IgM antibody titers against EBV docking/fusion proteins (gp350, gh/gp42, gh/gL/gp42), immediate early antigen (BZLF1), early antigens (EA p85, EA P138, EA P54), capsid antigens (VCA P18, VCA P23, VCA gp125) and late antigens (EBNA1) were measured. Specific EBNA1 and GlialCAM, CRYAB and ANO2 peptides were synthesized and also incorporated in our custom magnetic bead based multiplex assay. We observed significantly elevated IgG antibody titers in EBV-positive controls, RRMS with and without relapse, SPMS and PPMS patients for all lifecycle antigens except for several early antigens when compared to EBV-negative controls. Significantly higher IgG antibody titers were observed in RRMS patients for fusion proteins and EBNA1 peptides when compared to EBV-positive controls. An MS specific response was observed for ANO2 but not for GlialCAM or CRYAB. No significant treatment effects or a specific IgM response were detectable. The MS-specific, differential antibody response to EBV antigens confirms an altered immunological response to EBV in MS patients. EBV reactivation does not appear to play an important role in MS pathogenesis and no differential antibody signatures were observed between MS disease phases. The MS-specific anti-ANO2 antibody response suggests a potential role for EBNA1 as an antigenic driver, although the exact role of anti-ANO2 antibodies needs to be determined. The precise pathophysiological role of EBV in MS remains uncertain and requires further investigation.

TMEM16B (ANO2) is the Ca2+-activated chloride channel expressed in multiple brain regions, including the amygdala. Here we report that Ano2 knockout mice exhibit impaired anxiety-related behaviors and context-independent fear memory, thus implicating TMEM16B in anxiety modulation. We found that TMEM16B is expressed in somatostatin-positive (SOM+) GABAergic neurons of the central lateral amygdala (CeL), and its activity modulates action potential duration and inhibitory postsynaptic current (IPSC). We further provide evidence for TMEM16B actions not only in the soma but also in the presynaptic nerve terminals of GABAergic neurons. Our study reveals an intriguing role for TMEM16B in context-independent but not context-dependent fear memory, and supports the notion that dysfunction of the amygdala contributes to anxiety-related behaviors.

Specialized Ca 2+ -dependent ion channels ubiquitously couple intracellular Ca 2+ signals to a change in cell polarization. The existing physiological evidence suggests that Ca 2+ -activated Cl − channels (CaCCs) are functional in taste cells. Because Ano1 and Ano2 encode channel proteins that form CaCCs in a variety of cells, we analyzed their expression in mouse taste cells. Transcripts for Ano1 and Ano2 were detected in circumvallate (CV) papillae, and their expression in taste cells was confirmed using immunohistochemistry. When dialyzed with CsCl, taste cells of the type III exhibited no ion currents dependent on cytosolic Ca 2+ . Large Ca 2+ -gated currents mediated by TRPM5 were elicited in type II cells by Ca 2+ uncaging. When TRPM5 was inhibited by triphenylphosphine oxide (TPPO), ionomycin stimulated a small but resolvable inward current that was eliminated by anion channel blockers, including T16Ainh-A01 (T16), a specific Ano1 antagonist. This suggests that CaCCs, including Ano1-like channels, are functional in type II cells. In type I cells, CaCCs were prominently active, blockable with the CaCC antagonist CaCCinh-A01 but insensitive to T16. By profiling Ano1 and Ano2 expressions in individual taste cells, we revealed Ano1 transcripts in type II cells only, while Ano2 transcripts were detected in both type I and type II cells. P2Y agonists stimulated Ca 2+ -gated Cl − currents in type I cells. Thus, CaCCs, possibly formed by Ano2, serve as effectors downstream of P2Y receptors in type I cells. While the role for TRPM5 in taste transduction is well established, the physiological significance of expression of CaCCs in type II cells remains to be elucidated.