Involvement of ANO1 currents in pacemaking of PDGFRα-positive specialised smooth muscle cells in rat caudal epididymis

The epididymal duct exhibits spontaneous phasic contractions (SPCs) to store and transport sperm. Here, we explored molecular identification of pacemaker cells driving SPCs in the caudal epididymal duct and also investigated properties of pacemaker currents underlying SPCs focusing on ANO1 Ca2+-activated Cl- channels (CaCCs). Immunohistochemistry was performed to visualise the distribution of platelet-derived growth factor receptor α (PDGFRα)- or ANO1-positive cells in the rat caudal epididymal duct. Perforated whole-cell patch clamp technique was applied to enzymatically isolated epididymal cells, while SPCs were recorded with video edge-tracking technique. Immunohistochemistry revealed the distribution of α-smooth muscle actin (α-SMA)-positive cells co-expressing both PDGFRα and ANO1 in the innermost smooth muscle layer. Approximately one-third of isolated epididymis cells exhibited spontaneous transient inward currents (STICs) at the holding potential -60 mV. The reversal potential for STICs was close to the calculated chloride equivalent potential depending on intracellular Cl- concentrations. Ani9 (3 µM), the ANO1 specific inhibitor, decreased both amplitude and frequency of STICs, while cyclopiazonic acid (CPA, 30 µM), a sarco-/endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor, abolished STICs. Ani9 (3 or 10 µM) reduced the frequency of SPCs without changing their amplitude. Thus, PDGFRα+, ANO1+ specialised smooth muscle cells (SMCs) appear to function as pacemaker cells to electrically drive epididymal SPCs by generating ANO1-dependnet STICs. STICs arising from spontaneous Ca2+ release from intracellular Ca2+ store and subsequent opening of ANO1 result in depolarisations that spread into adjacent SMCs where L-type voltage-dependent Ca2+ channels are activated to develop SPCs.

Dissection of a CTCF topological boundary uncovers principles of enhancer-oncogene regulation

Enhancer-gene communication is dependent on topologically associating domains (TADs) and boundaries enforced by the CCCTC-binding factor (CTCF) insulator, but the underlying structures and mechanisms remain controversial. Here, we investigate a boundary that typically insulates fibroblast growth factor (FGF) oncogenes but is disrupted by DNA hypermethylation in gastrointestinal stromal tumors (GISTs). The boundary contains an array of CTCF sites that enforce adjacent TADs, one containing FGF genes and the other containing ANO1 and its putative enhancers, which are specifically active in GIST and its likely cell of origin. We show that coordinate disruption of four CTCF motifs in the boundary fuses the adjacent TADs, allows the ANO1 enhancer to contact FGF3, and causes its robust induction. High-resolution micro-C maps reveal specific contact between transcription initiation sites in the ANO1 enhancer and FGF3 promoter that quantitatively scales with FGF3 induction such that modest changes in contact frequency result in strong changes in expression, consistent with a causal relationship.

Establishing an ANO1-Based Cell Model for High-Throughput Screening Targeting TRPV4 Regulators

Transient receptor potential vanilloid 4 (TRPV4) is a widely expressed cation channel that plays an important role in many physiological and pathological processes. However, most TRPV4 drugs carry a risk of side effects. Moreover, existing screening methods are not suitable for the high-throughput screening (HTS) of drugs. In this study, a cell model and HTS method for targeting TRPV4 channel drugs were established based on a calcium-activated chloride channel protein 1 Anoctamin 1 (ANO1) and a double mutant (YFP-H148Q/I152L) of the yellow fluorescent protein (YFP). Patch-clamp experiments and fluorescence quenching kinetic experiments were used to verify that the model could sensitively detect changes in intracellular Ca2+ concentration. The functionality of the TRPV4 cell model was examined through temperature variations and different concentrations of TRPV4 modulators, and the performance of the model in HTS was also evaluated. The model was able to sensitively detect changes in the intracellular Ca2+ concentration and also excelled at screening TRPV4 drugs, and the model was more suitable for HTS. We successfully constructed a drug cell screening model targeting the TRPV4 channel, which provides a tool to study the pathophysiological functions of TRPV4 in vitro.

Function and Regulation of the Calcium-Activated Chloride Channel Anoctamin 1 (TMEM16A)

Various human tissues express the calcium-activated chloride channel Anoctamin 1 (ANO1), also known as TMEM16A. ANO1 allows the passive chloride flux that controls different physiological functions ranging from muscle contraction, fluid and hormone secretion, gastrointestinal motility, and electrical excitability. Overexpression of ANO1 is associated with pathological conditions such as hypertension and cancer. The molecular cloning of ANO1 has led to a surge in structural, functional, and physiological studies of the channel in several tissues. ANO1 is a homodimer channel harboring two pores - one in each monomer - that work independently. Each pore is activated by voltage-dependent binding of two intracellular calcium ions to a high-affinity-binding site. In addition, the binding of phosphatidylinositol 4,5-bisphosphate to sites scattered throughout the cytosolic side of the protein aids the calcium activation process. Furthermore, many pharmacological studies have established ANO1 as a target of promising compounds that could treat several illnesses. This chapter describes our current understanding of the physiological roles of ANO1 and its regulation under physiological conditions as well as new pharmacological compounds with potential therapeutic applications.

MiR-671-5p sponging activity of circMMP1 promotes esophageal squamous cancer progression

BACKGROUND

The aim of this study was to explore the function and mechanism of circular RNA (circRNA) matrix metallopeptidase 1 (circMMP1) in the progression of esophageal squamous cell carcinoma (ESCC).

METHODS

CircMMP1 expression was detected by quantitative real-time PCR (qRT-PCR), and its relationship with the prognosis of ESCC patients was evaluated by Kaplan-Meier analysis. Cells were transfected using corresponding plasmids, and the cell proliferation activity, migration and invasion capabilities in vitro were assessed. The protein level in tissues and cells was analyzed using western blotting. RNA pulldown, dual-luciferase reporter assay and RNA immunoprecipitation assay were performed in ESCC cells to detect the interaction between circMMP1 and miR-671-5p, or the correlation between miR-671-5p and ANO1. Xenograft tumor experiment was carried out to uncover the function of circMMP1 in vivo.

RESULTS

The high level of circMMP1 in tumor tissues was associated with poor prognoses of ESCC patients. Knockdown of circMMP1 suppressed ESCC cell proliferation, migration and invasion in vitro. MiR-671-5p was the target of circMMP1 and mediated the inhibition effect of circMMP1 on ESCC cells. CircMMP1 targeted miR-671-5p to regulate ANO1 expression, which was downstream of miR-671-5p. Overexpression of ANO1 weakened tumor-repressive function of circMMP1 knockdown in ESCC cells. Moreover, silencing of circMMP1 impeded ESCC tumor growth in vivo.

CONCLUSION

Our study provided novel evidence that circMMP1 accelerated ESCC progression by acting as a miR-671-5p sponge to enhance ANO1 expression.

Niclosamide potentiates TMEM16A and induces vasoconstriction

The TMEM16A calcium-activated chloride channel is a promising therapeutic target for various diseases. Niclosamide, an anthelmintic medication, has been considered as a TMEM16A inhibitor for treating asthma and chronic obstructive pulmonary disease, but was recently found to possess broad-spectrum off-target effects. Here we show that, under physiological conditions, niclosamide acutely potentiates TMEM16A without having any inhibitory effect. Our computational and functional characterizations pinpoint a putative niclosamide binding site on the extracellular side of TMEM16A. Mutations in this site attenuate the potentiation. Moreover, niclosamide potentiates endogenous TMEM16A in vascular smooth muscle cells, triggers intracellular calcium increase, and constricts the murine mesenteric artery. Our findings advise caution when considering niclosamide as a TMEM16A inhibitor to treat diseases such as asthma, COPD, and hypertension. The identification of the putative niclosamide binding site provides insights into the mechanism of TMEM16A pharmacological modulation, shining light on developing specific TMEM16A modulators to treat human diseases.

ANO1-Mediated Inhibition of Cancer Ferroptosis Confers Immunotherapeutic Resistance through Recruiting Cancer-Associated Fibroblasts

The application of immunotherapy in gastrointestinal (GI) cancers remains challenging because of the limited response rate and emerging therapeutic resistance. Combining clinical cohorts, multi-omics study, and functional/molecular experiments, it is found that ANO1 amplification or high-expression predicts poor outcomes and resistance to immunotherapy for GI cancer patients. Knocking-down or inhibiting ANO1 suppresses the growth/metastasis/invasion of multiple GI cancer cell lines, cell-derived xenograft, and patient-derived xenograft models. ANO1 contributes to an immune-suppressive tumor microenvironment and induces acquired resistance to anti-PD-1 immunotherapy, while ANO1 knockdown or inhibition enhances immunotherapeutic effectiveness and overcomes resistance to immunotherapy. Mechanistically, through inhibiting cancer ferroptosis in a PI3K-Akt signaling-dependent manner, ANO1 enhances tumor progression and facilitates cancer-associated fibroblast recruitment by promoting TGF-β release, thus crippling CD8+ T cell-mediated anti-tumor immunity and generating resistance to immunotherapy. This work highlights ANO1's role in mediating tumor immune microenvironment remodeling and immunotherapeutic resistance, and introduces ANO1 as a promising target for GI cancers' precision treatment.

A Novel ANO1 Gene Variant is Associated with Intestinal Dysmotility Syndrome Masquerading as Hirschsprung Disease: A Case Report

Anoctamin 1 (ANO1)-related intestinal dysmotility syndrome (OMIM: 620045) is an extremely rare disorder with only 2 cases reported in the medical literature. We present the clinical scenario of a 2-month-old male infant that presented to our center with diarrhea, vomiting, and abdominal distension. Routine investigations did not yield a clear diagnosis. Whole-exome sequencing showed a novel homozygous nonsense ANO1 pathogenic variant (c.1273G>T) with a protein alternation of p.Glu425Ter that fits the patient's phenotype. Sanger sequencing revealed the same ANO1 variant in both parents in a heterozygous form confirming an autosomal recessive mode of inheritance. The patient experienced multiple bouts of diarrhea-related metabolic acidosis, dehydration, and severe electrolyte imbalances that required intensive care unit monitoring. The patient was managed conservatively and being followed regularly in an outpatient setting.

Discovery of ANO1 Inhibitors based on Machine learning and molecule docking simulation approaches

Calcium-activated chloride channels (CaCCs) are chloride channels that are regulated according to intracellular calcium ion concentrations. The channel protein ANO1 is widely present in cells and is involved in physiological activities including cellular secretion, signaling, cell proliferation and vasoconstriction and diastole. In this study, the ANO1 inhibitors were investigated with machine learning and molecular simulation. Two-dimensional structure-activity relationship (2D-SAR) and three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed for the qualitative and quantitative prediction of ANO1 inhibitors. The results showed that the prediction accuracies of the model were 85.9% and 87.8% for the training and test sets, respectively, and 85.9% and 87.8% for the rotating forest (RF) in the 2D-SAR model. The CoMFA and CoMSIA methods were then used for 3D QSAR modeling of ANO1 inhibitors, respectively. The q² coefficients for model cross-validation were all greater than 0.5, implying that we were able to obtain a stable model for drug activity prediction. Molecular docking was further used to simulate the interactions between the five most promising compounds predicted by the model and the ANO1 protein. The total score for the docking results between all five compounds and the target protein was greater than 6, indicating that they interacted strongly in the form of hydrogen bonds. Finally, simulations of amino acid mutations around the docking cavity of the target proteins showed that each molecule had two or more sites of reduced affinity following a single mutation, indicating outstanding specificity of the screened drug molecules and their protein ligands.

High level of ANO1 promotes pancreatic cancer growth in concert with oncogenic KRAS

BACKGROUND

Anoctamin-1 (ANO1) was identified as an unfavorable prognostic marker in pancreatic cancer. However, the exact implication of ANO1 in pancreatic cancer is still poorly understood. Here we investigated the effect of ANO1 in pancreatic cancer progression under the context of oncogenic KRAS, aiming at finding a new therapeutic target.

METHODS

Knockdown and overexpression of oncogenic KRAS as well as ANO1 in PDAC cell lines were performed by lentivirus infection. Cell proliferation and migration assay, RNA seq analysis were performed in PDAC cells bearing different status of ANO1 and KRAS. In vivo mice model was used to investigate the xenograft tumor growth with different status of KRAS and ANO1.

RESULTS

Our results showed that ANO1 expression level is elevated in poorly differentiated cancer cells. Overexpression of ANO1 in PDAC cancer cells was found to promote cancer cell proliferation in vitro and in vivo, which synergized with the introduction of oncogenic KRAS. Consistently, knockdown of ANO1 expression was found to suppress cancer growth in vitro and in vivo. RNA seq analysis revealed that the observed synergistic cancer-promoting effect from ANO1 and oncogenic KRAS is likely due to concurrent activating key genes involved in lipid metabolism including HMGCS1.

CONCLUSION

The outcome from our study suggests that ANO1 plays an important role in promoting pancreatic cancer development, especially at the presence of oncogenic KRAS. Considering the prevalence of KRAS mutation in pancreatic cancer patients, suppression ANO1 may represent a potential effective therapeutic measure in pancreatic cancer treatment.

De novo 11q13.3q13.4 deletion in a patient with Fanconi renotubular syndrome and intellectual disability: Case report and review of literature

Objective

To explore the genetic etiology of a child with facial dysmorphia, developmental delay, intellectual disability, Fanconi renotubular syndrome, and Chiari malformations.

Materials and methods

Whole exome sequencing (WES), Copy number variation sequencing (CNV-seq), and mitochondrial gene detection (Long-PCR + NGS) were applied to detect possible pathogenic mutations and chromosomal copy number variations (CNVs), together with databases and literature reviews to clarify the pathological significance of the candidate mutations.

Results

The WES revealed a 2.10 Mb interstitial deletion from 11q13.3 to 11q13.4, which was later confirmed by CNV-seq involving 11 OMIM genes, among which SHANK2, DHCR7, NADSYN1, FADD, NUMA1, IL18BP, ANO1, and FGF3 are disease-causing. The mitochondrial gene shows no variations.

Conclusion

The child has carried a de novo 11q13.3q13.4 microdeletion, in which SHANK2 genes may be the key gene responsible for the phenotype of intellectual disability. The renal manifestation of the child, which can be diagnosed as Fanconi renotubular syndrome, has an unknown cause but may result from the effect of the ANO1 gene. This case adds a new phenotype to the deletion of this region.

The Novel lncRNA ENST00000530525 Affects ANO1, Contributing to Blood-Brain Barrier Injury in Cultured hCMEC/D3 Cells Under OGD/R Conditions

Ischemic stroke (IS) is a major neurological disease with high fatality and residual disability burdens. Long noncoding RNAs (lncRNAs) have been found to play an important role in IS. However, the roles and significance of most lncRNAs in IS are still unknown. This study was performed to identify differentially expressed (DE) lncRNAs using a lncRNA microarray in whole blood samples of patients suffering from acute cerebral ischemia. Bioinformatics analyses, including GO, KEGG pathway enrichment analysis, and proximity to putative stroke risk location analysis were performed. The novel lncRNA, ENST00000530525, significantly decreased after IS. Furthermore, we evaluated lncRNA ENST00000530525 expression in cultured hCMEC/D3 cells under oxygen-glucose deprivation/reoxygenation (OGD/R) conditions using fluorescent in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (RT-qPCR) analysis. To investigate the function of lncRNA ENST00000530525, its over-expression (OE) and negative control (NC) plasmids were transfected into hCMEC/D3 cells, and cell viability was detected by a cell counting kit-8 (CCK-8) assay after OGD/R. LncRNA ENST00000530525 and ANO1 expression were investigated using RT-qPCR and immunofluorescence. For blood-brain barrier (BBB) permeability, FITC-dextran transendothelial permeability assay and tight junction (TJ) protein immunofluorescence assays were performed. There were 3352 DE lncRNAs in the blood samples of acute IS patients. The validation results were consistent with the gene chip data. The GO and KEGG results showed that these lncRNAs were mainly related to oxygen and glucose metabolism, leukocyte transendothelial migration, mitophagy and cellular senescence. Among these, lncRNA ENST00000530525 was the most highly downregulated lncRNA and it was mapped within the IS-associated gene anoctamin-1 (ANO1). We further found that lncRNA ENST00000530525 was downregulated in hCMEC/D3 cells under 4 h OGD and 20 h reoxygenation (OGD4/R20) conditions. Upregulating lncRNA ENST00000530525 by plasmid transfection decreased cell viability while increasing ANO1 expression and it contributed to BBB injury in hCMEC/D3 cells after OGD4/R20. The lncRNA ENST00000530525 might play deleterious roles in post-stroke pathogenesis. These results show that some DE lncRNAs in humans participate through characteristic roles in post-stroke pathogenesis; thus, the roles and significance of some novel lncRNAs in IS warrant further study.

ANO1: More Than Just Calcium-Activated Chloride Channel in Cancer

ANO1, a calcium-activated chloride channel (CACC), is also known as transmembrane protein 16A (TMEM16A). It plays a vital role in the occurrence, development, metastasis, proliferation, and apoptosis of various malignant tumors. This article reviews the mechanism of ANO1 involved in the replication, proliferation, invasion and apoptosis of various malignant tumors. Various molecules and Stimuli control the expression of ANO1, and the regulatory mechanism of ANO1 is different in tumor cells. To explore the mechanism of ANO1 overexpression and activation of tumor cells by studying the different effects of ANO1. Current studies have shown that ANO1 expression is controlled by 11q13 gene amplification and may also exert cell-specific effects through its interconnected protein network, phosphorylation of different kinases, and signaling pathways. At the same time, ANO1 also resists tumor apoptosis and promotes tumor immune escape. ANO1 can be used as a promising biomarker for detecting certain malignant tumors. Further studies on the channels and the mechanism of protein activity of ANO1 are needed. Finally, the latest inhibitors of ANO1 are summarized, which provides the research direction for the tumor-promoting mechanism of ANO1.

VI-116, A Novel Potent Inhibitor of VRAC with Minimal Effect on ANO1

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.

Role of ANO1 in tumors and tumor immunity

Dysregulation of gene amplification, cell-signaling-pathway transduction, epigenetic and transcriptional regulation, and protein interactions drives tumor-cell proliferation and invasion, while ion channels also play an important role in the generation and development of tumor cells. Overexpression of Ca²⁺-activated Cl- channel anoctamin 1 (ANO1) is shown in numerous cancer types and correlates with poor prognosis. However, the mechanisms involved in ANO1-mediated malignant cellular transformation and the role of ANO1 in tumor immunity remain unknown. In this review, we discuss recent studies to determine the role of ANO1 in tumorigenesis and provide novel insights into the role of ANO1 in the context of tumor immunity. Furthermore, we analyze the roles and potential mechanisms of ANO1 in different types of cancers, and provide novel notions for the role of ANO1 in the tumor microenvironment and for potential use of ANO1 in clinical applications. Our review shows that ANO1 is involved in tumor immunity and microenvironment, and may, therefore, be an effective biomarker and therapeutic drug target.

Molecular dynamics simulation of TMEM16A channel: Linking structure with gating

TMEM16A, the calcium-activated chloride channel, is broadly expressed and plays pivotal roles in diverse physiological processes. To understand the structural and functional relationships of TMEM16A, it is necessary to fully clarify the structural basis of the gating of the TMEM16A channel. Herein, we performed the protein electrostatic analysis and molecular dynamics simulation on the TMEM16A in the presence and absence of Ca²⁺. Data showed that the separation of TM4 and TM6 causes pore expansion, and Q646 may be a key residue for the formation of π-helix in the middle segment of TM6. Moreover, E705 was found to form a group of H-bond interactions with D554/K588/K645 below the hydrophobic gate to stabilize the closed conformation of the pore in the Ca²⁺-free state. Interestingly, in the Ca²⁺ bound state, the E705 side chain swings 100^o to serve as Ca²⁺-binding coordination and released K645. K645 is closer to the hydrophobic gate in the calcium-bound state, which facilitates the provision of electrostatic forces for chloride ions as the ions pass through the hydrophobic gate. Our findings provide the structural-based insights to understanding the mechanisms of gating of TMEM16A.

Molecular mechanisms of activation and regulation of ANO1-Encoded Ca2+-Activated Cl- channels

Ca2+-activated Cl- channels (CaCCs) perform a multitude of functions including the control of cell excitability, regulation of cell volume and ionic homeostasis, exocrine and endocrine secretion, fertilization, amplification of olfactory sensory function, and control of smooth muscle cell contractility. CaCCs are the translated products of two members (ANO1 and ANO2, also known as TMEM16A and TMEM16B) of the Anoctamin family of genes comprising ten paralogs. This review focuses on recent progress in understanding the molecular mechanisms involved in the regulation of ANO1 by cytoplasmic Ca2+, post-translational modifications, and how the channel protein interacts with membrane lipids and protein partners. After first reviewing the basic properties of native CaCCs, we then present a brief historical perspective highlighting controversies about their molecular identity in native cells. This is followed by a summary of the fundamental biophysical and structural properties of ANO1. We specifically address whether the channel is directly activated by internal Ca2+ or indirectly through the intervention of the Ca2+-binding protein Calmodulin (CaM), and the structural domains responsible for Ca2+- and voltage-dependent gating. We then review the regulation of ANO1 by internal ATP, Calmodulin-dependent protein kinase II-(CaMKII)-mediated phosphorylation and phosphatase activity, membrane lipids such as the phospholipid phosphatidyl-(4,5)-bisphosphate (PIP2), free fatty acids and cholesterol, and the cytoskeleton. The article ends with a survey of physical and functional interactions of ANO1 with other membrane proteins such as CLCA1/2, inositol trisphosphate and ryanodine receptors in the endoplasmic reticulum, several members of the TRP channel family, and the ancillary Κ+ channel β subunits KCNE1/5.

Evidence for tetrodotoxin-resistant spontaneous myogenic contractions of mouse isolated stomach that are dependent on acetylcholine

Background and Purpose

Gastric pacemaker cells, interstitial cells of Cajal (ICC), are believed to initiate myogenic (non‐neuronal) contractions. These become damaged in gastroparesis, associated with dysrhythmic electrical activity and nausea. We utilised mouse isolated stomach to model myogenic contractions and investigate their origin and actions of interstitial cells of Cajal modulators.

Experimental Approach

Intraluminal pressure was recorded following distension with a physiological volume; tone, contraction amplitude and frequency were quantified. Compounds were bath applied.

Key Results

The stomach exhibited regular large amplitude contractions (median amplitude 9.0 [4.7–14.8] cmH₂O, frequency 2.9 [2.5–3.4] c.p.m; n = 20), appearing to progress aborally. Tetrodotoxin (TTX, 10⁻⁶ M) had no effect on tone, frequency or amplitude but blocked responses to nerve stimulation. ω‐conotoxin GVIA (10⁻⁷ M) ± TTX was without effect on baseline motility. In the presence of TTX, (1) atropine (10⁻¹⁰–10⁻⁶ M) reduced contraction amplitude and frequency in a concentration‐related manner (pIC₅₀ 7.5 ± 0.3 M for amplitude), (2) CaCC channel (previously ANO1) inhibitors MONNA and CaCCinh‐A01 reduced contraction amplitude (significant at 10⁻⁵, 10⁻⁴ M respectively) and frequency (significant at 10⁻⁵ M), and (3), neostigmine (10⁻⁵ M) evoked a large, variable, increase in contraction amplitude, reduced by atropine (10⁻⁸–10⁻⁶ M) but unaffected (exploratory study) by the H1 receptor antagonist mepyramine (10⁻⁶ M).

Conclusions and Implications

The distended mouse stomach exhibited myogenic contractions, resistant to blockade of neural activity by TTX. In the presence of TTX, these contractions were prevented or reduced by compounds blocking interstitial cells of Cajal activity or by atropine and enhanced by neostigmine (antagonised by atropine), suggesting involvement of non‐neuronal ACh in their regulation.

Cepharanthine, a novel selective ANO1 inhibitor with potential for lung adenocarcinoma therapy

Anoctamin-1 (ANO1), also known as transmembrane protein 16A (TMEM16A), is identified as a Ca²⁺-activated Cl^- channel that is expressed in many organs and tissues. It is involved in numerous major physiological functions and especially in tumor growth. By screening 530 natural compounds, we identified cepharanthine as a potent blocker of ANO1 channels with an IC₅₀ of 11.2 ± 0.9 μM and E_max of 92.7 ± 1.7%. The Lys³⁸⁴, Arg⁵³⁵, Thr⁵³⁹, and Glu⁶²⁴ in ANO1 are critical for the inhibitory effect of cepharanthine. Similar to its effect on ANO1, cepharanthine inhibits ANO2, the closest analog of TMEM16A. In contrast, up to 30 μM of cepharanthine showed limited inhibitory effects on recombinant ANO6 and bestrophin-1-encoded Ca²⁺-activated Cl^- currents, but it showed no effects on endogenous volume-regulated anion currents (VRAC). Cepharanthine could also potently suppress endogenous ANO1 currents, significantly inhibit cell proliferation and migration, and induce apoptosis in LA795 lung adenocarcinoma cells. Moreover, animal experiments have shown that cepharanthine can dramatically inhibit the growth of xenograft tumors in mice. The high specificity provided by cepharanthine could be an important foundation for future studies of the physiological role of ANO1 channels, and these findings may reveal a new mechanism of its anticancer effect.

Functional expression of TMEM16A in taste bud cells

Key points

Taste transduction occurs in taste buds in the tongue epithelium.

The Ca²⁺‐activated Cl^– channels TMEM16A and TMEM16B play relevant physiological roles in several sensory systems.

Here, we report that TMEM16A, but not TMEM16B, is expressed in the apical part of taste buds.

Large Ca²⁺‐activated Cl⁻ currents blocked by Ani‐9, a selective inhibitor of TMEM16A, are measured in type I taste cells but not in type II or III taste cells.

ATP indirectly activates Ca²⁺‐activated Cl^– currents in type I cells through TMEM16A channels.

These results indicate that TMEM16A is functional in type I taste cells and contribute to understanding the largely unknown physiological roles of these cells.

Abstract

The Ca²⁺‐activated Cl^– channels TMEM16A and TMEM16B have relevant roles in many physiological processes including neuronal excitability and regulation of Cl^– homeostasis. Here, we examined the presence of Ca²⁺‐activated Cl^– channels in taste cells of mouse vallate papillae by using immunohistochemistry and electrophysiological recordings. By using immunohistochemistry we showed that only TMEM16A, and not TMEM16B, was expressed in taste bud cells where it largely co‐localized with the inwardly rectifying K⁺ channel KNCJ1 in the apical part of type I cells. By using whole‐cell patch‐clamp recordings in isolated cells from taste buds, we measured an average current of −1083 pA at −100 mV in 1.5 μm Ca²⁺ and symmetrical Cl^– in type I cells. Ion substitution experiments and blockage by Ani‐9, a specific TMEM16A channel blocker, indicated that Ca²⁺ activated anionic currents through TMEM16A channels. We did not detect any Ca²⁺‐activated Cl^– currents in type II or III taste cells. ATP is released by type II cells in response to various tastants and reaches type I cells where it is hydrolysed by ecto‐ATPases. Type I cells also express P2Y purinergic receptors and stimulation of type I cells with extracellular ATP produced large Ca²⁺‐activated Cl⁻ currents blocked by Ani‐9, indicating a possible role of TMEM16A in ATP‐mediated signalling. These results provide a definitive demonstration that TMEM16A‐mediated currents are functional in type I taste cells and provide a foundation for future studies investigating physiological roles for these often‐neglected taste cells.

Taste transduction occurs in taste buds in the tongue epithelium.

The Ca²⁺‐activated Cl^– channels TMEM16A and TMEM16B play relevant physiological roles in several sensory systems.

Here, we report that TMEM16A, but not TMEM16B, is expressed in the apical part of taste buds.

Large Ca²⁺‐activated Cl⁻ currents blocked by Ani‐9, a selective inhibitor of TMEM16A, are measured in type I taste cells but not in type II or III taste cells.

ATP indirectly activates Ca²⁺‐activated Cl^– currents in type I cells through TMEM16A channels.

These results indicate that TMEM16A is functional in type I taste cells and contribute to understanding the largely unknown physiological roles of these cells.

Development of a QPatch-Automated Electrophysiology Assay for Identifying TMEM16A Small-Molecule Inhibitors

The calcium-activated chloride channel, TMEM16A, is involved in airway hydration and bronchoconstriction and is a promising target for respiratory disease. Drug development efforts around channels require an electrophysiology-based assay for identifying inhibitors or activators. TMEM16A has proven to be a difficult channel to record on automated electrophysiology platforms due to its propensity for rundown. We developed an automated, whole-cell, electrophysiology assay on the QPatch-48 to evaluate small-molecule inhibitors of TMEM16A. In this assay, currents remained stable for a duration of roughly 11 min, allowing for the cumulative addition of five concentrations of compounds and resulted in reproducible IC₅₀s. The absence of rundown was likely due to a low internal free-calcium level of 250 nM, which was high enough to produce large currents, but also maintained the voltage dependence of the channel. Current amplitude averaged 6 nA using the single-hole QPlate and the channel maintained outward rectification throughout the recording. Known TMEM16A inhibitors were tested and their IC₅₀s aligned with those reported in the literature using manual patch-clamp. Once established, this assay was used to validate novel TMEM16A inhibitors that were identified in our high-throughput fluorescent-based assay, as well as to assist in structure–activity relationship efforts by the chemists. Overall, we demonstrate an easy to operate, reproducible, automated electrophysiology assay using the QPatch-48 for TMEM16A drug development efforts.

The Ca2+-activated chloride channel ANO1/TMEM16A: An emerging therapeutic target for epithelium-originated diseases?

Anoctamin 1 (ANO1) or TMEM16A gene encodes a member of Ca²⁺ activated Cl^– channels (CaCCs) that are critical for physiological functions, such as epithelial secretion, smooth muscle contraction and sensory signal transduction. The attraction and interest in ANO1/TMEM16A arise from a decade long investigations that abnormal expression or dysfunction of ANO1 is involved in many pathological phenotypes and diseases, including asthma, neuropathic pain, hypertension and cancer. However, the lack of specific modulators of ANO1 has impeded the efforts to validate ANO1 as a therapeutic target. This review focuses on the recent progress made in understanding of the pathophysiological functions of CaCC ANO1 and the current modulators used as pharmacological tools, hopefully illustrating a broad spectrum of ANO1 channelopathy and a path forward for this target validation.

Opposing roles of E3 ligases TRIM23 and TRIM21 in regulation of ion channel ANO1 protein levels

Anoctamin-1 (ANO1) (TMEM16A) is a calcium-activated chloride channel that plays critical roles in diverse physiological processes, such as sensory transduction and epithelial secretion. ANO1 levels have been shown to be altered under physiological and pathological conditions, although the molecular mechanisms that control ANO1 protein levels remain unclear. The ubiquitin–proteasome system is known to regulate the levels of numerous ion channels, but little information is available regarding whether and how ubiquitination regulates levels of ANO1. Here, we showed that two E3 ligases, TRIM23 and TRIM21, physically interact with the C terminus of ANO1. In vitro and in vivo assays demonstrated that whereas TRIM23 ubiquitinated ANO1 leading to its stabilization, TRIM21 ubiquitinated ANO1 and induced its degradation. Notably, ANO1 regulation by TRIM23 and TRIM21 is involved in chemical-induced pain sensation, salivary secretion, and heart-rate control in mice, and TRIM23 also mediates ANO1 upregulation induced by epidermal growth factor treatment. Our results suggest that these two antagonistic E3 ligases act together to control ANO1 expression and function. Our findings reveal a previously unrecognized mechanism for regulating ANO1 protein levels and identify a potential molecular link between ANO1 regulation, epidermal growth factor, and other signaling pathways.

ANO1 Expression Orchestrates p27Kip1/MCL1-Mediated Signaling in Head and Neck Squamous Cell Carcinoma

Simple Summary

Our aim was to elucidate the molecular mechanisms of how ANO1 contributes to oncogenic processes in squamous cell carcinoma of the head and neck (HNSCC). We explored transcriptional programs influenced by ANO1 knockdown in patient-derived UT-SCC cell lines with 11q13 amplification and ANO1 overexpression. ANO1 depletion led to downregulation of broad pro-survival BCL2 family protein members, including MCL1, and simultaneously induced upregulation of the cell cycle inhibitor p27^Kip1 and its redistribution from the cytoplasm into the nucleus in the studied HNSCC cells. Gene set enrichment analysis highlighted pathways associated with perturbed cell cycle and apoptosis in the ANO1-depleted samples. Silencing of ANO1 and application of an ANO1-targeting small-molecule inhibitor led to ANO1 degradation and reduction of cell viability. These findings suggest that ANO1 has drug target potential that deserves further evaluation in preclinical in vivo models.

Abstract

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of tumors that derive from the mucosal epithelium of the upper aerodigestive tract and present high mortality rate. Lack of efficient targeted-therapies and biomarkers towards patients’ stratification are caveats in the disease treatment. Anoctamin 1 (ANO1) gene is amplified in 30% of HNSCC cases. Evidence suggests involvement of ANO1 in proliferation, migration, and evasion of apoptosis; however, the exact mechanisms remain elusive. Aim of this study was to unravel the ANO1-dependent transcriptional programs and expand the existing knowledge of ANO1 contribution to oncogenesis and drug response in HNSCC. We cultured two HNSCC cell lines established from primary tumors harboring amplification and high expression of ANO1 in three-dimensional collagen. Differential expression analysis of ANO1-depleted HNSCC cells demonstrated downregulation of MCL1 and simultaneous upregulation of p27^Kip1 expression. Suppressing ANO1 expression led to redistribution of p27^Kip1 from the cytoplasm to the nucleus and associated with a cell cycle arrested phenotype. ANO1 silencing or pharmacological inhibition resulted in reduction of cell viability and ANO1 protein levels, as well as suppression of pro-survival BCL2 family proteins. Collectively, these data provide insights of ANO1 involvement in HNSCC carcinogenesis and support the rationale that ANO1 is an actionable drug target.

Anoctamin 1 antagonism potentiates conventional tocolytic-mediated relaxation of pregnant human uterine smooth muscle

BACKGROUND

Currently available tocolytic agents are not effective treatment for preterm labor beyond 48 h. A major reason is the development of maternal side effects which preclude the maintenance of an effective steady-state drug concentration. One strategy that can mitigate these side effects is utilizing synergistic drug combinations to reduce the drug concentrations necessary to elicit a clinical effect. We have previously shown that three anoctamin 1 (ANO1) antagonists mediate potent relaxation of precontracted human uterine smooth muscle (USM). In this study, we aimed to determine whether a combination of sub-relaxatory doses of tocolytic drugs in current clinical use [the L-type voltage-gated calcium channel (VGCC) blocker, nifedipine (NIF); and the β2-adrenergic (β2AR) agonist, terbutaline (TRB)] will potentiate USM relaxation with two ANO1 antagonists [benzbromarone (BB) and MONNA (MN)].

OBJECTIVE

This study sought to examine the synergistic potency and mechanistic basis of two ANO1 antagonists with currently available tocolytic drugs. Functional endpoints assessed included relaxation of pre-contracting pregnant human USM tissue, inhibition of intracellular calcium release, and reduction of spontaneous transient inward current (STIC) recordings in human uterine smooth muscle cells.

METHODS

Human myometrial strips and primary human USM cells were used in organ bath and calcium flux experiments with different combinations of sub-threshold doses of ANO1 antagonists and terbutaline or nifedipine to determine if ANO1 antagonists potentiate tocolytic drugs.

RESULTS

The combination of sub-threshold doses of two ANO1 antagonists and current tocolytic drugs demonstrate a significant degree of synergy to relax human pregnant USM compared to the effects achieved when these drugs are administered individually.

CONCLUSION

A combination of sub-threshold doses of VGCC blocker and β2AR agonist with ANO1 antagonists potentiates relaxation of oxytocin-induced contractility and calcium flux in human USM ex vivo. Our findings may serve as a foundation for novel tocolytic drug combinations.

LncRNA GIHCG Promotes the Development of Esophageal Cancer by Modulating miR-29b-3p/ANO1 Axis

Background

Esophageal cancer is one of the most frequent cancers with a higher mortality worldwide. Although many long non-coding RNAs (LncRNAs) are reported to play important roles in the progression of esophageal cancer, the function of lncRNA GIHCG in esophageal cancer remains unclear.

Methods

The expression of GIHCG in esophageal cancer tissues and cancer cell lines was detected by qRT-PCR. Cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8) assay, EdU staining assay and colony formation assay. Cell invasion and migration were measured by transwell assay. Cell apoptosis was detected by a flow cytometer. Luciferase reporter assay and RIP assay were used to determine the interaction between GIHCG and miR-29b-3p, and their subsequent regulation of anoctamin 1 (ANO1). The expression of ANO1 in esophageal cancer tissues and cell lines was detected by Western blot. The effect of GIHCG/miR-29b-3p in tumor formation was assessed by the xenograft nude mice model in vivo.

Results

GIHCG was significantly upregulated in esophageal cancer tissues and relevant cancer cell lines. Downregulation of GIHCG significantly inhibited the growth, colony formation, invasion, migration and induced apoptosis of esophageal cancer cells in vitro. Bioinformatic analysis and RIP assay determined that GIHCG was a sponge of miR-29b-3p, and ANO1 was a direct target of miR-29b-3p. Moreover, functional experiments showed that GIHCG upregulated ANO1 expression by directly sponging miR-29b-3p. Furthermore, in vivo experiment revealed that knockdown of GIHCG significantly inhibited tumor growth in nude mice.

Conclusion

Our study revealed that lncRNA GIHCG promoted the progression of esophageal cancer by targeting the miR-29b-3p/ANO1 axis, suggesting that GIHCG might be a novel therapeutic target for esophageal cancer.

Ca2+ Dependence of Volume-Regulated VRAC/LRRC8 and TMEM16A Cl- Channels

All vertebrate cells activate Cl- currents (ICl ,swell) when swollen by hypotonic bath solution. The volume-regulated anion channel VRAC has now been identified as LRRC8/SWELL1. However, apart from VRAC, the Ca2+-activated Cl- channel (CaCC) TMEM16A and the phospholipid scramblase and ion channel TMEM16F were suggested to contribute to cell swelling-activated whole-cell currents. Cell swelling was shown to induce Ca2+ release from the endoplasmic reticulum and to cause subsequent Ca2+ influx. It is suggested that TMEM16A/F support intracellular Ca2+ signaling and thus Ca2+-dependent activation of VRAC. In the present study, we tried to clarify the contribution of TMEM16A to ICl ,swell. In HEK293 cells coexpressing LRRC8A and LRRC8C, we found that activation of ICl ,swell by hypotonic bath solution (Hypo; 200 mosm/l) was Ca2+ dependent. TMEM16A augmented the activation of LRRC8A/C by enhancing swelling-induced local intracellular Ca2+ concentrations. In HT29 cells, knockdown of endogenous TMEM16A attenuated ICl ,swell and changed time-independent swelling-activated currents to VRAC-typical time-dependent currents. Activation of ICl ,swell by Hypo was attenuated by blocking receptors for inositol trisphosphate and ryanodine (IP3R; RyR), as well as by inhibiting Ca2+ influx. The data suggest that TMEM16A contributes directly to ICl ,swell as it is activated through swelling-induced Ca2+ increase. As activation of VRAC is shown to be Ca2+-dependent, TMEM16A augments VRAC currents by facilitating Hypo-induced Ca2+ increase in submembraneous signaling compartments by means of ER tethering.

A paradoxical increase of force development in saphenous and tail arteries from heterozygous ANO1 knockout mice

A Ca²⁺‐activated Cl⁻ channel protein, ANO1, is expressed in vascular smooth muscle cells where Cl⁻ current is thought to potentiate contraction by contributing to membrane depolarization. However, there is an inconsistency between previous knockout and knockdown studies on ANO1’s role in small arteries. In this study, we assessed cardiovascular function of heterozygous mice with global deletion of exon 7 in the ANO1 gene. We found decreased expression of ANO1 in aorta, saphenous and tail arteries from heterozygous ANO1 knockout mice in comparison with wild type. Accordingly, ANO1 knockdown reduced the Ca²⁺‐activated Cl⁻ current in smooth muscle cells. Consistent with conventional hypothesis, the contractility of aorta from ANO1 heterozygous mice was reduced. Surprisingly, we found an enhanced contractility of tail and saphenous arteries from ANO1 heterozygous mice when stimulated with noradrenaline, vasopressin, and K⁺‐induced depolarization. This difference was endothelium‐independent. The increased contractility of ANO1 downregulated small arteries was due to increased Ca²⁺ influx. The expression of L‐type Ca²⁺ channels was not affected but expression of the plasma membrane Ca²⁺ ATPase 1 and the Piezo1 channel was increased. Expressional analysis of tail arteries further suggested changes of ANO1 knockdown smooth muscle cells toward a pro‐contractile phenotype. We did not find any difference between genotypes in blood pressure, heart rate, pressor response, and vasorelaxation in vivo. Our findings in tail and saphenous arteries contrast with the conventional hypothesis and suggest additional roles for ANO1 as a multifunctional protein in the vascular wall that regulates Ca²⁺ homeostasis and smooth muscle cell phenotype.

[Expression of ANO1 during cardiac fibroblasts differentiation and its electrophysiological characteristics as calcium-activated chloride channel protein]

OBJECTIVE

To investigate the expression and electrophysiological characteristics of calcium-activated chlorine channel anoctamin-1 (ANO1) protein during the differentiation of cardiac fibroblasts (CFs) into myofibroblasts (MFs), and to elucidate the role of ANO1 in myocardial fibrosis.

METHODS

The primary CFs from neonatal rats were isolated and the cells differentiated into MFs by subculture. The Ca²⁺-activated Cl^- current (I_Cl(Ca)) in CFs and MFs were measured by whole-cell patch clamp, and the expressions of ANO1, α-smooth muscle actin(α-SMA)and vimentin in CFs and MFs were detected by immunofluorescence assay and Western blot, respectively.

RESULTS

The current density in the early adherent CFs was stronger than that in MFs. ANO1 was expressed preferentially within and around the nuclei, and a small amount of ANO1 was expressed on the cell membrane. Moreover, ANO1 expression was weak in the early adherent CFs and displayed stronger expression in the MFs with proliferation tendency.

CONCLUSION

The expression of ANO1 is closely related to the differentiation of MFs and it may be involved in modulation myocardial fibrosis.

ANO1 regulates cardiac fibrosis via ATI-mediated MAPK pathway

Cardiac fibrosis is associated with most of heart diseases, but its molecular mechanism remains unclear. Anoctamin-1 (ANO1), a calcium-activated chloride channels (CaCCs) protein, plays a critical role in various pathophysiological processes. In the current study, we identified ANO1 expression in myocardial infarction (MI) model of rat and verified the role of ANO1 in cardiac fibrosis using transcriptomics combined with RNAi assays. we found that ANO1 expression was increased during the first two weeks, and decreased in the third week after MI. Fluorescence double labeling showed that ANO1 was mainly expressed in cardiac fibroblasts (CFs) and displayed an increased expression in CFs with proliferation tendency. The proliferation and secretion of CFs were markedly inhibited by knockdown of ANO1. RNA-Seq showed that most of the downregulation genes were related to the proliferation of CFs and cardiac fibrosis. After ANO1 knockdown, the expressions of angiotensin II type 1 receptor (AT1R) and cell nuclear proliferation antigen were markedly reduced, and the phosphorylation levels of MEK and ERK1/2 was decreased significantly, indicating that ANO1 regulate cardiac fibrosis through ATIR-mediated MAPK signaling pathway. These findings would be useful for the development of therapeutic strategies targeting ANO1 to treat and prevent cardiac fibrosis.

Investigating the regulatory function of the ANO1-AS2 on the ANO1 gene in infertile men with asthenozoospermia and terato-asthenozoospermia

Long non-coding RNAs (lncRNAs) have a particular expression in the testicular tissue and exhibit a regulatory function on the reproduction system. ANO1-AS2 (linc02584), as an lncRNA is located near the anoctamin1 (ANO1) gene. ANO1 is an important component of the transmembrane system exhibiting expression modifications in the idiopathic infertile men. Therefore, the present study was conducted to investigate the relationship between ANO1-AS2 and ANO1 gene expression with sperm motility and morphology in the patients with asthenozoospermia (AZ) and terato- asthenozoospermia (TAZ). The study population included 32 patients with AZ, 35 patients with TAZ, and 34 people with normozoospermia (NZ, control). The expression levels of ANO1 gene and ANO1-AS2 in the spermatozoa were measured by the quantitative real-time polymerase chain reaction (PCR). Docking analysis was performed to investigate the interactions of the ANO1 gene promoter and intermediate elements with ANO1-AS2. ANO1 gene expression was significantly (P < 0.05) downregulated in the patients however; ANO1-AS2 expression was significantly upregulated (P < 0.05). The subsequent analysis confirmed the inverse correlation between ANO1 and ANO1-AS2. ANO1 gene expression level was significantly positively correlated with sperm motility and morphology (P < 0.05). Moreover, ANO1-AS2 expression showed an inverse correlation with sperm motility and morphology (P < 0.05). Docking analysis confirmed that ANO1-AS2 could stably interact with ANO1 gene promoter. In conclusion, ANO1-AS2 is likely to downregulate the ANO1 gene by interacting with ANO1 gene promoter, which can influence the sperm motility and morphology.

Suppression of CaMKIIβ Inhibits ANO1-Mediated Glioblastoma Progression

ANO1, a Ca²⁺-activated chloride channel, is highly expressed in glioblastoma cells and its surface expression is involved in their migration and invasion. However, the regulation of ANO1 surface expression in glioblastoma cells is largely unknown. In this study, we found that Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) β specifically enhances the surface expression and channel activity of ANO1 in U251 glioblastoma cells. When KN-93, a CaMKII inhibitor, was used to treat U251 cells, the surface expression and channel activity of ANO1 were significantly reduced. Only CaMKIIβ, among the four CaMKII isoforms, increased the surface expression and channel activity of ANO1 in a heterologous expression system. Additionally, gene silencing of CaMKIIβ suppressed the surface expression and channel activity of ANO1 in U251 cells. Moreover, gene silencing of CaMKIIβ or ANO1 prominently reduced the migration and invasion of U251 and U87 MG glioblastoma cells. We thus conclude that CaMKIIβ plays a specific role in the surface expression of ANO1 and in the ANO1-mediated tumorigenic properties of glioblastoma cells, such as migration and invasion.

LRRCA8A and ANO1 contribute to serum-induced VRAC in a Ca2+-dependent manners

The volume-regulated anion channel (VRAC) plays a central role in maintaining cell volume in response to osmotic stress. Leucine-rich repeat-containing 8A (LRRC8A) was recently identified as an essential component of VRAC although other Cl^- channels were also suggested to contribute to VRAC. VRAC is activated when a cell is challenged with a hypotonic environment or even in isotonic conditions challenged with different stimuli. It is not clear how VRAC is activated and whether activation of VRAC in hypotonic and isotonic conditions share the same mechanism. In this present study, we investigated relative contribution of LRRC8A and anoctamin 1(ANO1) to VRAC currents activated by fetal bovine serum (FBS) in isotonic condition, and studied the role of intracellular Ca²⁺ in this activation. We used CRISPR/Cas9 gene editing approach, electrophysiology, and pharmacology approaches to show that VRAC currents induced by FBS is mostly mediated by LRRC8A in HEK293 cells, but also with significant contribution from ANO1. FBS induces Ca²⁺ transients and these Ca²⁺ signals are required for the activation of VRAC by serum. These findings will help to further understand the mechanism in activation of VRAC.

Na+/Ca2 + Exchange and Pacemaker Activity of Interstitial Cells of Cajal

Interstitial cells of Cajal (ICC) are pacemaker cells that generate electrical slow waves in gastrointestinal (GI) smooth muscles. Slow waves organize basic motor patterns, such as peristalsis and segmentation in the GI tract. Slow waves depend upon activation of Ca²⁺-activated Cl^– channels (CaCC) encoded by Ano1. Slow waves consist of an upstroke depolarization and a sustained plateau potential that is the main factor leading to excitation-contraction coupling. The plateau phase can last for seconds in some regions of the GI tract. How elevated Ca²⁺ is maintained throughout the duration of slow waves, which is necessary for sustained activation of CaCC, is unknown. Modeling has suggested a role for Na⁺/Ca²⁺ exchanger (NCX) in regulating CaCC currents in ICC, so we tested this idea on murine intestinal ICC. ICC of small and large intestine express NCX isoforms. NCX3 is closely associated with ANO1 in ICC, as shown by immunoprecipitation and proximity ligation assays (PLA). KB-R7943, an inhibitor of NCX, increased CaCC current in ICC, suggesting that NCX, acting in Ca²⁺ exit mode, helps to regulate basal [Ca²⁺]_i in these cells. Shifting NCX into Ca²⁺ entry mode by replacing extracellular Na⁺ with Li⁺ increased spontaneous transient inward currents (STICs), due to activation of CaCC. Stepping ICC from −80 to −40 mV activated slow wave currents that were reduced in amplitude and duration by NCX inhibitors, KB-R7943 and SN-6, and enhanced by increasing the NCX driving force. SN-6 reduced the duration of clustered Ca²⁺ transients that underlie the activation of CaCC and the plateau phase of slow waves. Our results suggest that NCX participates in slow waves as modeling has predicted. Dynamic changes in membrane potential and ionic gradients during slow waves appear to flip the directionality of NCX, facilitating removal of Ca²⁺ during the inter-slow wave interval and providing Ca²⁺ for sustained activation of ANO1 during the slow wave plateau phase.

Integrated analysis of genomic and transcriptomic profiles identified a prognostic immunohistochemistry panel for esophageal squamous cell cancer

Background

The poor outcome of patients with esophageal squamous cell carcinoma (ESCC) highlights the importance of the identification of novel effective prognostic biomarkers. We aimed to identify a clinically applicable prognostic immunohistochemistry (IHC) panel for ESCC.

Methods

An integrated analysis was performed to screen and establish a prognostic panel using exome sequencing profile from 81 pairs of ESCC samples and RNA expression microarray data from 119 ESCC subjects. Two independent ESCC cohorts were recruited as training and validation groups to test the prognostic value.

Results

Three genes were selected, namely, ANO1, GAL, and MMP3, which were aberrantly expressed in ESCC tumor tissues (P < .001). Among them, ANO1 and MMP3 were reserved for the construction of the prognostic panel due to their significant association with the prognosis of ESCC patients (P = .015 and P < .001). Patients with both ANO1+ and MMP3+ had a poorer prognosis than that with ANO1−/MMP3+, ANO1+/MMP3−, or ANO1−/MMP3 − in both the training set and validation set (P < .001). Receiver operating characteristic analysis showed that the combination of IHC panel and eighth American Joint Commission on Cancer staging yielded a better prognostic predictive efficacy compared with the two indexes alone (P < .001, area under curve: 0.752). Finally, a nomogram was created by integrating the IHC markers and clinicopathological risk factors to predict prognosis with a C‐index of 0.695 (95% confidence interval: 0.657‐0.734).

Conclusion

Using an integrated multistage screening strategy, we identified and validated a valuable prognostic IHC panel for ESCC.

Agonism of the TMEM16A calcium-activated chloride channel modulates airway smooth muscle tone

TMEM16A (anoctamin 1) is an important calcium-activated chloride channel in airway smooth muscle (ASM). We have previously shown that TMEM16A antagonists such as benzbromarone relax ASM and have proposed TMEM16A antagonists as novel therapies for asthma treatment. However, TMEM16A is also expressed on airway epithelium, and TMEM16A agonists are being investigated as novel therapies for cystic fibrosis. There are theoretical concerns that agonism of TMEM16A on ASM could lead to bronchospasm, making them detrimental as airway therapeutics. The TMEM16A agonist Eact induced a significant contraction of human ASM and guinea pig tracheal rings in an ex vivo organ bath model. Pretreatment with two different TMEM16A antagonists, benzbromarone or T16Ainh-A01, completely attenuated these Eact-induced contractions. Pretreatment with Eact alone augmented the maximum acetylcholine contraction. Pretreatment of A/J mice in vivo with nebulized Eact caused an augmentation of methacholine-induced increases in airway resistance measured by the forced oscillatory technique (flexiVent). Pretreatment with the TMEM16A antagonist benzbromarone significantly attenuated methacholine-induced increases in airway resistance. In in vitro cellular studies, TMEM16A was found to be expressed more abundantly in ASM compared with epithelial cells in culture (8-fold higher in ASM). Eact caused an increase in intracellular calcium in human ASM cells that was completely attenuated by pretreatment with benzbromarone. Eact acutely depolarized the plasma membrane potential of ASM cells, which was attenuated by benzbromarone or nifedipine. The TMEM16A agonist Eact modulates ASM contraction in both ex vivo and in vivo models, suggesting that agonism of TMEM16A may lead to clinically relevant bronchospasm.

Fusobacterium nucleatum prevents apoptosis in colorectal cancer cells via the ANO1 pathway

Objective

: Chemotherapy failure derived from drug resistance is the most important reason causing the recurrence in colorectal cancer patients. Therefore, it is necessary to shed light on the mechanism of chemotherapy resistance in colorectal cancer patients.

Methods

: We looked into the contribution of Fusobacterium nucleatum and ANO1 to chemoresistance in the human colorectal carcinoma cell lines. We silence and overexpress ANO1 in HCT116 and HT29 cells with lentivirus and siRNA knockdown technique in the absence or presence of F. nucleatum, oxaliplatin or 5-fluorouracil (5-FU). ANO1, p-pg, cleaved PARP, cleaved caspase-3, and EGFR expression was measured by Western blot. Cell apoptosis was measured by flow cytometry.

Results

: We found that F. nucleatum promoted ANO1 expression on colon cancer cells. Moreover, ANO1 prevent colon cancer apoptosis from oxaliplatin and 5-FU. Additionally, knockdown ANO1 expression could block F. nucleatum protective effects and increase the apoptosis effects induced by oxaliplatin and 5-FU. Therefore, F. nucleatum might be biologically involved in the development of colon cancer chemoresistance via ANO1 pathway.

Conclusions

: Taken together, our findings provide a valuable insight into clinical management and therapy, which may ameliorate colorectal cancer patient outcomes.

Functional comparison of anoctamin 1 antagonists on human uterine smooth muscle contractility and excitability

Background: Pre-term birth is a major health care challenge throughout the world, and preterm labor represents a potentially reversible component of this problem. Current tocolytics do not improve preterm labor beyond 48 h. We have previously shown that anoctamin 1 (ANO1) channel blockade results in relaxation of pre-contracted human uterine smooth muscle (USM). Three drug classes with reported medicinal effects in humans also have members with ANO1 antagonism. In this study, we compared the ability of representatives from these 3 classes to reduce human USM contractility and excitability. Objective: This study sought to examine the comparative potency of 3 ANO1 antagonists on pregnant human USM relaxation, contraction frequency reduction, inhibition of intracellular calcium release and membrane hyperpolarization. Methods: Experiments were performed using: 1) Ex vivo organ bath (human pregnant tissue), 2) Oxytocin-induced calcium flux (in vitro human USM cells) and 3) Membrane potential assay (in vitro human USM cells). Results: Benzbromarone (BB) demonstrated the greatest potency among the compounds tested with respect to force, frequency inhibition, reducing calcium elevation and depolarizing membrane potential. Conclusion: While all 3 ANO1 antagonists attenuate pregnant human uterine tissue contractility and excitability, BB is the most potent tocolytic drug. Our findings may serve as a foundation for future structure-function analyses for novel tocolytic drug development.

Emerging Perspectives on Pain Management by Modulation of TRP Channels and ANO1

Receptor-type ion channels are critical for detection of noxious stimuli in primary sensory neurons. Transient receptor potential (TRP) channels mediate pain sensations and promote a variety of neuronal signals that elicit secondary neural functions (such as calcitonin gene-related peptide [CGRP] secretion), which are important for physiological functions throughout the body. In this review, we focus on the involvement of TRP channels in sensing acute pain, inflammatory pain, headache, migraine, pain due to fungal infections, and osteo-inflammation. Furthermore, action potentials mediated via interactions between TRP channels and the chloride channel, anoctamin 1 (ANO1), can also generate strong pain sensations in primary sensory neurons. Thus, we also discuss mechanisms that enhance neuronal excitation and are dependent on ANO1, and consider modulation of pain sensation from the perspective of both cation and anion dynamics.

Generation of Spontaneous Tone by Gastrointestinal Sphincters

An important feature of the gastrointestinal (GI) muscularis externa is its ability to generate phasic contractile activity. However, in some GI regions, a more sustained contraction, referred to as "tone," also occurs. Sphincters are muscles oriented in an annular manner that raise intraluminal pressure, thereby reducing or blocking the movement of luminal contents from one compartment to another. Spontaneous tone generation is often a feature of these muscles. Four distinct smooth muscle sphincters are present in the GI tract: the lower esophageal sphincter (LES), the pyloric sphincter (PS), the ileocecal sphincter (ICS), and the internal anal sphincter (IAS). This chapter examines how tone generation contributes to the functional behavior of these sphincters. Historically, tone was attributed to contractile activity arising directly from the properties of the smooth muscle cells. However, there is increasing evidence that interstitial cells of Cajal (ICC) play a significant role in tone generation in GI muscles. Indeed, ICC are present in each of the sphincters listed above. In this chapter, we explore various mechanisms that may contribute to tone generation in sphincters including: (1) summation of asynchronous phasic activity, (2) partial tetanus, (3) window current, and (4) myofilament sensitization. Importantly, the first two mechanisms involve tone generation through summation of phasic events. Thus, the historical distinction between "phasic" versus "tonic" smooth muscles in the GI tract requires revision. As described in this chapter, it is clear that the unique functional role of each sphincter in the GI tract is accompanied by a unique combination of contractile mechanisms.

Telocytes express ANO-1-encoded chloride channels in canine ventricular myocardium

INTRODUCTION

It is unknown if ANO-1 is expressed in the heart, though the presence of a calcium-activated chloride current has been proposed to mediate some cardiac dysrhythmias. Furthermore, a specific cell type termed telocytes, morphologically mimicking Cajal cells which use ANO-1 to modulate their pacemaker activity in the gut, have been described in the heart. We therefore sought to determine whether this channel is expressed in the canine heart.

METHODS

Myocardium was sampled from the ventricles of five canines. Sections were labeled with anti-Kit and anti-ANO-1 antibodies. Slides were reviewed by four investigators looking at cell morphology, distribution, and co-localization. Identification of telocytes was based on criteria including morphology, Kit positivity (+), and ANO-1 positivity (+).

RESULTS

Clusters of cells meeting criteria for telocytes were seen in the epicardium, sub-epicardium, and mid-myocardium. A small subset of cells that were morphologically similar to myocytes was ANO-1 (+) but Kit (-). In total, three different cell classes were found: (i) Kit (+), ANO-1 (+) cells with the appearance of telocytes; (ii) Kit (+), ANO-1 (-) cells; and (iii) Kit (-), ANO-1 (+) cells with the morphologic appearance of cardiac myocytes.

CONCLUSIONS

Telocytes are present in the canine ventricle and express ANO-1. These data merit further study to elucidate the functional expression of these channels in the heart and whether they may be targets for cardiac arrhythmias.

Transcriptional activation of ANO1 promotes gastric cancer progression

The prognosis of gastric cancer (GC) remains poor due to local invasion and distal metastasis. The GC-related molecular mechanisms underlying invasion and metastasis are not well understood. In this study, we investigated the functional role of ANO1 in GC progression. We found that ANO1 is overexpressed in GC tissues and correlated with GC tumor-node-metastasis stage. Knockdown of ANO1 significantly inhibited GC cell migration and invasion in vitro, and loss of ANO1 resulted in inhibition of tumor metastasis in vivo. Mechanistically, SP1 increased ANO1 transcription, recruited MLL1 to the ANO1 promoter region, facilitated H3K4 trimethylation, and subsequently promoted ANO1 expression. Together, our findings provide a mechanistic assessment of ANO1 overexpression, which represents a GC progression-related molecule and a potentially valuable target for future research.

Contribution of Anoctamins to Cell Survival and Cell Death

Before anoctamins (TMEM16 proteins) were identified as a family of Ca²⁺-activated chloride channels and phospholipid scramblases, the founding member anoctamin 1 (ANO1, TMEM16A) was known as DOG1, a marker protein for gastrointestinal stromal tumors (GIST). Meanwhile, ANO1 has been examined in more detail, and the role of ANO1 in cell proliferation and the development of different types of malignomas is now well established. While ANO5, ANO7, and ANO9 may also be relevant for growth of cancers, evidence has been provided for a role of ANO6 (TMEM16F) in regulated cell death. The cellular mechanisms by which anoctamins control cell proliferation and cell death, respectively, are just emerging; however, the pronounced effects of anoctamins on intracellular Ca²⁺ levels are likely to play a significant role. Recent results suggest that some anoctamins control membrane exocytosis by setting Ca²⁺_i levels near the plasma membrane, and/or by controlling the intracellular Cl^- concentration. Exocytosis and increased membrane trafficking induced by ANO1 and ANO6 may enhance membrane expression of other chloride channels, such as CFTR and volume activated chloride channels (VRAC). Notably, ANO6-induced phospholipid scrambling with exposure of phosphatidylserine is pivotal for the sheddase function of disintegrin and metalloproteinase (ADAM). This may support cell death and tumorigenic activity of IL-6 by inducing IL-6 trans-signaling. The reported anticancer effects of the anthelminthic drug niclosamide are probably related to the potent inhibitory effect on ANO1, apart from inducing cell cycle arrest through the Let-7d/CDC34 axis. On the contrary, pronounced activation of ANO6 due to a large increase in intracellular calcium, activation of phospholipase A2 or lipid peroxidation, can lead to ferroptotic death of cancer cells. It therefore appears reasonable to search for both inhibitors and potent activators of TMEM16 in order to interfere with cancer growth and metastasis.

Inhibition of Ca2+ -activated chloride channel ANO1 suppresses ovarian cancer through inactivating PI3K/Akt signaling

Most common ovarian cancers are epithelial carcinoma in which the etiology for carcinogenesis remains elusive. ANO1/TMEM16A, a member of Ca²⁺ -activated Cl^- channels (CaCCs), has been demonstrated to promote epithelium-originated cancers and whether it plays a role in the pathogenesis of ovarian cancer is unknown. In our study we found that ANO1 proteins were overexpressed in human epithelial ovarian cancer cells and tissue samples. ANO1 protein upregulation was correlated with the clinical FIGO (International Federation of Gynecology and Obstetrics) staging and poor grade in ovarian cancer tissues. Interestingly, the upregulation of ANO1 gene expression was also detected in the peripheral blood mononuclear cells (PBMCs) from preoperative patients with ovarian tumors, and the down-regulation of ANO1 in the PBMCs from postoperative patients. Silencing of ANO1 inhibited proliferation and invasion of ovarian cancer cells. Mechanistically, ANO1 knockdown attenuated phosphorylation of PI3K/Akt, and inhibition of PI3K/Akt signaling by specific inhibitor LY294002 resulted in suppression of ovarian cancer cells growth promoted by ANO1 expression. Furthermore, intratumoral injection of ANO1 siRNA suppressed subcutaneous xenograft tumor growth in nude mice implanted with ovarian cancer SKOV3 cells. Taken together, our findings demonstrate that ANO1 overexpression is involved in the pathogenesis of human epithelial ovarian cancer. Inhibition of ANO1 upregulation or inactivating PI3K/Akt signaling may have therapeutic potential for epithelial ovarian cancer, and the detection of ANO1 expression level in PBMCs from patients may also serve as a biomarker for diagnosis and prognosis of epithelial ovarian cancers.

Exploiting the Diversity of Ion Channels: Modulation of Ion Channels for Therapeutic Indications

Ion channels are macromolecular proteins that form water-filled pores in cell membranes and they are critical for a variety of physiological and pharmacological functions. Dysfunctional ion channels can cause diseases known as channelopathies. Ion channels are encoded by approximately 400 genes, representing the second largest class of proven drug targets for therapeutic areas including neuropsychiatric disorders, cardiovascular and metabolic diseases, immunological diseases, nephrological diseases, gastrointestinal diseases, pulmonary/respiratory diseases, and many cancers. With more ion channel structures are being solved and functional robust assays are being developed, there are tremendous opportunities for identifying specific modulators targeting ion channels for new therapy.

Down-regulation of miR-9 promotes epithelial mesenchymal transition via regulating anoctamin-1 (ANO1) in CRC cells

MicroRNA-9 (miR-9) has been reported to play a suppressive or promoting role according to cancer type. In this study, we investigated the effects of anoctamin-1 (ANO1) and miR-9 on colorectal cancer (CRC) cell proliferation, migration, and invasion and determined the underlying molecular mechanisms. Thirty-two paired CRC tissues and adjacent normal tissues were analyzed for ANO1 expression using quantitative real-time PCR (qRT-PCR). HCT116 cells were transiently transfected with miR-9 mimic, miR-9 inhibitor, or si-ANO1. Cell proliferation was determined by MTT, and flow cytometric analysis, while cell migration and invasion were assayed by trans-well migration and invasion assay in HCT116 cells. ANO1 was validated as a target of miR-9 using luciferase reporter assay and bioinformatics algorithms. We found that ANO1 expression was up-regulated in CRC tissues compared with adjacent normal tissues. ANO1 expression was associated with advanced tumor stage and lymph node metastasis, and there was an inverse relationship between miR-9 and ANO1 mRNA expression in CRC specimens, but no significant difference was found between miR-9 and ANO1 expression. ANO1 is a direct target of miR-9, and overexpression of miR-9 suppressed both mRNA and protein expression of ANO1 and inhibited cell proliferation, migration, and invasion of HCT116 cells. We also showed that overexpression of miR-9 suppressed expression of p-AKT, cyclin D1, and p-ERK in HCT116 cells. We conclude that miR-9 inhibits CRC cell proliferation, migration, and invasion by directly targeting ANO1, and miR-9/ANO1 could be a potential therapeutic target for CRC.

Downregulation of microRNA-9 reduces inflammatory response and fibroblast proliferation in mice with idiopathic pulmonary fibrosis through the ANO1-mediated TGF-β-Smad3 pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with increasing occurrence, high death rates and unfavorable treatment regimens. In the current study, we identified the expression of microRNA-9 (miR-9) and anoctamin-1 (ANO1) in IPF mouse models induced by bleomycin, and their effects on inflammation and fibroblast proliferation through the transforming growth factor-β (TGF-β)-Smad3 pathway. To verify the targeting relationship between miR-9 and ANO1, we used bioinformatics prediction and conducted a dual-luciferase reporter gene assay. The underlying regulatory mechanisms of miR-9 and the target gene ANO1 were investigated mainly with the treatment of miR-9 mimic, miR-9 inhibitor, or siRNA against ANO1 in fibroblasts isolated from IPF mice. Enzyme-linked immunosorbent assay was performed to investigate the effect of miR-9 or ANO1 on inflammatory factors. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry were used to detect fibroblast proliferation and apoptosis. Reverse transcription quantitative polymerase chain reaction and western blot analysis were applied to measure the expression of the TGF-β-Smad3 pathway-related genes. The determination of luciferase activity suggested that miR-9 targets ANO1. Upregulation of miR-9 or silencing of ANO1 intensified inflammation in IPF, promoted proliferation and inhibited apoptotic ability of lung fibroblasts. MiR-9 negatively modulated ANO1, and thus activated the TGF-β-Smad3 pathway. These findings suggest that miR-9 can indirectly activate the TGF-β-Smad3 pathway by inhibiting the expression of ANO1, thereby aggravating inflammation, promotes proliferation and suppressing apoptosis of lung fibroblasts in mice models of IPF.

Flos Magnoliae Inhibits Chloride Secretion via ANO1 Inhibition in Calu-3 Cells

Flos Magnoliae (FM, Chinese name: Xin-yi) is an oriental medicinal herb commonly used for symptomatic relief from allergic rhinitis, sinusitis, and headache, including in traditional Chinese and Korean medicine formulations. FM inhibits histamine release from mast cells and cytokine secretion from T cells. However, the mechanism of action of FM on the anoctamin-1 (ANO1) ion channel, which is responsible for nasal hypersecretion in allergic rhinitis, has not been elucidated. Therefore, in this study, we investigated the effect of a 30% ethanolic extract of FM (FM_EtOH) and its chemical constituents on ANO1 activity. We used high-performance liquid chromatography analysis to identify five major chemical constituents of FM_EtOH: vanillic acid, tiliroside, eudesmin, magnolin, and fargesin. Using a conventional whole-cell patch clamp method, we found that FM_EtOH (30, 100, and 300[Formula: see text][Formula: see text]g/mL) and its chemical constituent tiliroside inhibited ANO1 activity in ANO1-overexpressing HEK293T cells. In addition, we found that the treatment of the airway epithelial cell line Calu-3 with interleukin 4 significantly increased Ca[Formula: see text] activated Cl[Formula: see text] current (I_CaCC), but not cystic fibrosis transmembrane conductance regulator (CFTR)-mediated chloride current (I_CFTR). FM_EtOH and tiliroside specifically inhibited I_CaCC. Thus, in this study, we identified a novel mechanism underlying the alleviation of allergic rhinitis by FM_EtOH. Our results indicate that FM_EtOH and its chemical constituent tiliroside are promising and potent agents for the prevention and treatment of allergic rhinitis.

Anoctamin Channels in Human Myometrium: A Novel Target for Tocolysis

BACKGROUND

Spontaneous preterm labor leading to preterm birth is a significant obstetric problem leading to neonatal morbidity and mortality. Current tocolytics are not completely effective and novel targets may afford a therapeutic benefit.

OBJECTIVE

To determine whether the anoctamin (ANO) family, including the calcium-activated chloride channel ANO1, is present in pregnant human uterine smooth muscle (USM) and whether pharmacological and genetic modulation of ANO1 modulates USM contraction.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR), quantitative RT-PCR, and immunohistochemical staining were done to determine which members of the ANO family are expressed in human USM. Uterine smooth muscle strips were studied in an organ bath to determine whether ANO1 antagonists inhibit oxytocin-induced USM contractions. Anoctamin 1 small interfering RNA (siRNA) knockdown was performed to determine its effect on filamentous-/globular (F/G)-actin ratio, a measurement of actin polymerization's role in promoting smooth muscle contraction.

RESULTS

Messenger RNA (mRNA) encoding all members of the ANO family (except ANO7) are expressed in pregnant USM tissue. Anoctamin 1 mRNA expression was decreased 15.2-fold in pregnant USM compared to nonpregnant. Anoctamin 1 protein is expressed in pregnant human USM tissue. Functional organ bath studies with pregnant human USM tissue demonstrated that the ANO1 antagonist benzbromarone attenuates the force and frequency of oxytocin-induced contractions. In human USM cells, siRNA knockdown of ANO1 decreases F-/G-actin ratios.

CONCLUSION

Multiple members of the ANO family, including the calcium-activated chloride channel ANO1, are expressed in human USM. Antagonism of ANO1 by pharmacological inhibition and genetic knockdown leads to an attenuation of contraction in pregnant human USM. Anoctamin 1 is a potentially novel target for tocolysis.