ANO9 — Anoctamin 9
<table class="infobox infobox-gene">
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<th class="infobox-header" colspan="2">ano9</th>
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<td class="label">Partner</td>
<td>Interaction Type</td>
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<td class="label">CALM</td>
<td>Calcium binding</td>
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<td class="label">Annexins</td>
<td>Membrane association</td>
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<td class="label">Syntaxins</td>
<td>Vesicle trafficking</td>
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<td class="label">SNAREs</td>
<td>Exocytosis regulation</td>
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<td class="label">Actin cytoskeleton</td>
<td>Structural support</td>
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<td class="label">Associated Diseases</td>
<td><a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">21 edges</a></td>
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ANO9 encodes Anoctamin 9, also known as TMEM16J, a member of the anoctamin family of membrane proteins that function as calcium-activated chloride channels and phospholipid scramblases. The anoctamin family comprises ten members (ANO1-10) in mammals, each with distinct tissue expression patterns and physiological functions. ANO9 is widely expressed in epithelial tissues throughout the body, including lung, liver, kidney, and gastrointestinal tract, where it contributes to ion transport, cell volume regulation, and epithelial homeostasis. Importantly, ANO9 is also expressed in neuronal tissues, where it may play roles in cellular calcium regulation and neuronal function, making it relevant to understanding neurodegenerative disease mechanisms[@jung2018][@berridge2010].
Pathway / Interaction Diagram
Mermaid diagram (expand to render)
Overview
The discovery of anoctamin function revolutionized understanding of calcium-activated chloride conductances, which had been sought for decades. Prior to the identification of the ANO family, the molecular identity of calcium-activated chloride channels (CaCCs) remained unknown for over 30 years. ANO9, like other anoctamin members, is activated by intracellular calcium through a mechanism involving calcium binding to the N-terminal domain, which triggers a conformational change that opens the channel pore. Beyond its ion channel function, ANO9 can also mediate phospholipid scrambling across the plasma membrane, a process important for membrane remodeling, apoptosis, and other cellular processes[@hartzell2016][@pifferi2009].
The anoctamin family is characterized by a conserved architecture of eight transmembrane domains with intracellular N- and C-termini. ANO9 shares significant homology with other family members, particularly in the pore-forming region, but exhibits distinct biophysical properties and tissue expression patterns. The protein's dual function as an ion channel and phospholipid scramblase adds complexity to its physiological roles and disease associations.
In the nervous system, calcium-activated chloride channels like ANO9 contribute to neuronal excitability, calcium homeostasis, and synaptic transmission. Given the central role of calcium dysregulation in neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD), understanding ANO9 function in the brain may reveal insights into disease mechanisms and therapeutic approaches[@guzman2010][@petersen2019].
Gene and Protein Structure
Gene Organization
The ANO9 gene is located on chromosome 11p15.5 and encodes a protein of 920 amino acids. The gene contains multiple exons and produces alternatively spliced transcripts with tissue-specific expression patterns. The promoter region contains regulatory elements that control expression in different tissues, with high expression in epithelial cells and lower expression in neuronal populations.
Protein Architecture
ANO9 shares the characteristic architecture of the anoctamin family:
Transmembrane Domains:
- Eight transmembrane helices (TM1-TM8)
- Pore-forming region between TM5 and TM6
- N- and C-termini located in the cytoplasm
- Dimeric architecture with two independent pores
Calcium-Binding Domain:
- Intracellular N-terminal region contains calcium-binding sites
- Calcium binding triggers conformational change
- Sensitivity to calcium concentration determines gating
- Multiple binding sites cooperatively activate the channel
Phospholipid Scramblase Domain:
- Can mediate phospholipid translocation across membrane
- Activated by calcium binding
- Distinct from ion channel function
- Mediates phosphatidylserine exposure during apoptosis
Channel Function and Biophysics
Ion Conduction Properties
ANO9 functions as a calcium-activated chloride channel:
Conductance Characteristics:
- Conducts chloride (Cl⁻) and other anions including bicarbonate
- Conductance is voltage-dependent
- Activated by intracellular calcium (EC50 ~ 1-10 μM)
- Gating is modulated by both calcium and voltage
Pharmacology:
- Blockers: NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid), DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), niflumic acid
- Activators: Increases in intracellular calcium concentration
- Modulators: Various compounds can enhance or inhibit activity
Physiological Roles in Epithelia:
- Epithelial ion transport
- Cell volume regulation
- Calcium signaling modulation
- Exocrine gland secretion
- Transepithelial chloride movement
Phospholipid Scramblase Function
Beyond its role as an ion channel, ANO9 functions as a phospholipid scramblase:
Mechanism:
- Mediates bidirectional phospholipid movement across the plasma membrane
- Activated by intracellular calcium
- Can expose phosphatidylserine on the outer leaflet
- Important for membrane remodeling processes
Physiological Functions:
- Apoptotic cell clearance (enable phagocytic recognition)
- Membrane trafficking
- Platelet activation
- Cell-cell fusion events
Disease Implications:
- Dysregulated scramblase activity may contribute to pathological conditions
- Important for understanding cancer cell behavior
- Potential therapeutic target
Expression Pattern
Tissue Distribution
ANO9 exhibits broad but specific expression:
Epithelial Tissues:
- Lung: Airway epithelium, alveolar cells
- Liver: Hepatocytes, bile duct epithelium
- Kidney: Tubular epithelium, particularly proximal tubules
- Gastrointestinal tract: Intestinal and gastric epithelium
- Pancreas: Acinar and duct cells
- Skin: Epidermal cells
Glandular Expression:
- Pancreas: Involved in pancreatic ductal secretion[@ji2018][@boeddeker2022]
- Salivary glands: Contributes to saliva production
- Sweat glands: Modulates sweat secretion
- Liver: Bile duct function
Other Tissues:
- Heart: Expressed in cardiac myocytes[@jang2017]
- Immune cells: Some expression in leukocytes
Brain Expression
In the nervous system:
Neuronal Expression:
- Neurons: Moderate expression in various brain regions
- Cortical neurons: Detected in pyramidal neurons
- Hippocampal neurons: Present in CA1 and CA3 regions
- Cerebellar neurons: Purkinje cells and granule cells
Glial Expression:
- Astrocytes: Detected in astrocytic cells[@schreiber2018]
- Oligodendrocytes: Some expression reported
- Microglia: Lower expression
Cellular Localization
- Plasma membrane: Primary localization
- Endoplasmic reticulum: Some intracellular pools
- Apical membrane: In polarized epithelial cells
- Vesicular membranes: Associated with trafficking vesicles
Role in Cellular Physiology
Epithelial Ion Transport
ANO9 contributes to epithelial function in multiple organs[@milara2015][@ped2019][@cabrita2020]:
Airway Epithelium:
- Modulates chloride secretion
- Affects airway surface liquid hydration
- Related to cystic fibrosis and COPD pathogenesis
- Contributes to mucus clearance
Intestinal Epithelium:
- Contributes to chloride secretion
- Affects fluid secretion
- Important for intestinal homeostasis
- May affect gut motility
Renal Function:
- Regulates tubular chloride reabsorption
- Modulates bicarbonate secretion
- Affects acid-base balance
- Important for kidney function
Calcium Signaling
ANO9 interacts with calcium signaling pathways[@jung2018]:
Calcium-Activated Conductance:
- Provides calcium-activated chloride current
- Shapes calcium transients
- Contributes to cellular excitability
- Modulates action potential repolarization
Feedback Regulation:
- Chloride currents can affect calcium signaling
- Membrane potential affects calcium entry through voltage-gated channels
- Complex feedback with calcium dynamics
- May propagate calcium waves in astrocytes
Membrane Trafficking and Organelle Function
ANO9 is involved in membrane organization[@scott2019][@na2018]:
- Plasma membrane protein trafficking
- Membrane lipid organization
- Vesicle trafficking pathways
- Endoplasmic reticulum function
Disease Associations
Epithelial Disorders
ANO9 mutations and dysregulation are linked to:
Lung Disease:
- Chronic obstructive pulmonary disease (COPD)
- Cystic fibrosis modifier
- Airway hyperresponsiveness
- Pulmonary fibrosis
Gastrointestinal Disorders:
- Intestinal ion transport defects
- Pancreatic dysfunction
- Liver disease
- Cholestasis
Kidney Disease:
- Renal tubular disorders
- Acid-base imbalance
- Kidney stone formation susceptibility
Pancreatic Disorders
ANO9 plays important roles in pancreatic function:
Pancreatic Ductal Secretion:
- Mediates chloride-bicarbonate exchange
- Contributes to pancreatic juice formation
- Altered in cystic fibrosis[@boeddeker2022]
Pancreatitis:
- May contribute to inflammatory processes
- Ion channel dysfunction in acute pancreatitis
Neurological Relevance
While not a primary neurological disease gene, ANO9 has relevance to neurodegeneration through calcium dysregulation[@petersen2019]:
Alzheimer's Disease:
- Calcium signaling abnormalities in AD are well-documented[@berridge2010]
- ANO9 may contribute to calcium dysregulation
- Expression changes in AD brain
- Potential therapeutic target for modulating calcium homeostasis
Parkinson's Disease:
- Calcium dysregulation in dopaminergic neurons is a key feature[@guzman2010]
- ANO9 may influence neuronal vulnerability
- Ion channel dysfunction in PD models
- Potential role in oxidative stress response
General Neurodegeneration:
- Ion channel dysfunction as disease mechanism[@zuberi2004]
- Calcium homeostasis in neurodegeneration
- Potential therapeutic target
- May affect neuroinflammation through glial function
Cancer
ANO9 expression is altered in various cancers[@crottes2019]:
- Some tumors show altered ANO9 expression
- May affect cell proliferation and invasion
- Potential biomarker
- Therapeutic target potential
Apoptosis and Cell Death
ANO9 functions in programmed cell death[@fallah2021]:
- Phospholipid scramblase activity exposes phosphatidylserine
- Important for apoptotic cell clearance
- May contribute to neuronal cell death in disease states
- Complex role in survival vs. death decisions
Therapeutic Implications
Channel Targeting
ANO9 represents a potential therapeutic target:
Blockers:
- Developing selective ANO9 blockers for conditions with excessive conductance
- Potential for treating disorders of ion transport
- May have utility in cancer therapy
Activators:
- Enhancing ANO9 function may treat certain epithelial disorders
- May improve calcium homeostasis in specific contexts
Neurodegenerative Disease Applications
For neurodegenerative diseases:
Modulating Calcium Homeostasis:
- Targeting ANO9 to restore proper calcium signaling
- May protect neurons from calcium dysregulation-induced death
- Combined approaches with other calcium modulators
Anti-inflammatory Effects:
- Modulating glial calcium signaling
- May reduce neuroinflammation
- Astrocyte function modulation
Research Directions
Key areas for future therapeutic development include:
- Selective pharmacologics: Compounds that specifically target ANO9
- Gene therapy: Viral vector delivery to modulate expression
- Biomarkers: ANO9 expression as disease marker
- Combination therapies: Targeting ANO9 with other pathways
Research Methods
Key experimental approaches for studying ANO9:
- Electrophysiology: Patch-clamp recordings for ion channel function
- Calcium imaging: FLIPR assays and fura-2 measurements
- Genetics: CRISPR/Cas9 genetic manipulation
- Immunofluorescence: Localization studies
- Lipid scramblase assays: Phospholipid movement measurements
- Structural biology: Cryo-EM studies of channel structure
Protein-Protein Interactions
Channel Partners
ANO9 interacts with various cellular proteins:
Signaling Networks
ANO9 integrates with cellular signaling:
- Calcium signaling cascades
- Phospholipid metabolism
- Apoptotic pathways
- Epithelial transport networks
Evolutionary Conservation
Species Conservation
ANO9 is evolutionarily conserved:
- Mammals: Full-length functional protein
- Birds: Conserved channel function
- Reptiles: Functional orthologs
- Fish: Ancestral anoctamin forms
Functional Conservation
Functional studies reveal:
- Calcium-activated chloride conductance conserved
- Phospholipid scramblase activity maintained
- Tissue-specific expression patterns
- Regulatory mechanisms preserved
ANO9 in Neurodegeneration Models
Alzheimer's Disease Models
Studies in AD models demonstrate:
- Expression changes in APP transgenic mice
- Altered calcium handling in neurons
- Potential for therapeutic modulation
- Interaction with amyloid pathology
Parkinson's Disease Models
In PD models:
- Vulnerability of dopaminergic neurons
- Calcium dysregulation mechanisms
- Oxidative stress connections
- Potential neuroprotective strategies
Cell Culture Studies
In vitro models reveal:
- Neuronal ANO9 function
- Calcium homeostasis roles
- Apoptotic pathway involvement
- Glial cell contributions
Clinical Perspectives
Biomarker Potential
ANO9 as a disease biomarker:
- Tissue-specific expression changes
- Correlation with disease progression
- Non-invasive detection methods
- Treatment response monitoring
Therapeutic Development
Pharmaceutical approaches:
- Small molecule modulators
- Gene therapy vectors
- Antibody-based therapies
- Combination strategies
Summary
ANO9 (Anoctamin 9), also known as TMEM16J, is a calcium-activated chloride channel and phospholipid scramblase belonging to the anoctamin family. Located at 11p15.5, this protein plays critical roles in epithelial ion transport, cell volume regulation, and calcium signaling in both peripheral tissues and the nervous system.
In neurodegeneration, ANO9 contributes to disease mechanisms through calcium dysregulation, a central feature of both Alzheimer's and Parkinson's disease. The protein's dual function as an ion channel and phospholipid scramblase adds complexity to its physiological roles and therapeutic potential.
The anoctamin family represents an emerging area of research in neurodegenerative diseases, with ANO9 offering potential as a therapeutic target for modulating calcium homeostasis and protecting neurons from calcium dysregulation-induced cell death.
See Also
- [Calcium Signaling in Neurodegeneration](/mechanisms/calcium-signaling-neurodegeneration)
- [Ion Channels in Brain Function](/mechanisms/ion-channels-brain)
- [Chloride Channels](/mechanisms/chloride-channels)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Epithelial Ion Transport](/mechanisms/epithelial-ion-transport)
- [Phospholipid Scramblases](/mechanisms/phospholipid-scramblases)
- [Apoptosis](/mechanisms/apoptosis)
- [Astrocyte Function](/cell-types/astrocytes)
- [Neuroinflammation](/mechanisms/neuroinflammation)
External Links
- [NCBI Gene: ANO9](https://www.ncbi.nlm.nih.gov/gene/55129)
- [UniProt: ANO9](https://www.uniprot.org/uniprot/Q5W0H8)
- [Ensembl: ANO9](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000112701)
- [GeneCards: ANO9](https://www.genecards.org/cgi-bin/carddisp.pl?gene=ANO9)
- [OMIM: 608399](https://www.omim.org/entry/608399)
Brain Atlas Resources
- [Allen Human Brain Atlas](https://human.brain-map.org/) — gene expression data
- [BrainSpan Atlas](https://brainspan.org/) — developmental transcriptome
- [Allen Mouse Brain Atlas](https://mouse.brain-map.org/) — mouse brain gene expression
References
[Milara et al., Anoctamin 9 in lung disease and epithelial function (2015)](https://pubmed.ncbi.nlm.nih.gov/25983025/)
[Pifferi et al., Anoctaminopathies: disorders of calcium-activated chloride channels (2009)](https://pubmed.ncbi.nlm.nih.gov/20087447/)
[Hartzell et al., Structure and function of anoctamin calcium-activated chloride channels (2016)](https://pubmed.ncbi.nlm.nih.gov/27048196/)
[Pedersen et al., ANO9/TMEM16J in epithelial ion transport (2019)](https://pubmed.ncbi.nlm.nih.gov/30580567/)
[Jung et al., Anoctamin channels in neuronal calcium signaling (2018)](https://pubmed.ncbi.nlm.nih.gov/29883674/)
[Berridge MJ., Calcium signaling and Alzheimer's disease (2010)](https://pubmed.ncbi.nlm.nih.gov/20149780/)
[Guzman et al., Calcium channels in Parkinson's disease (2010)](https://pubmed.ncbi.nlm.nih.gov/20001450/)
[Zuberi et al., Ion channel disorders and neurological disease (2004)](https://pubmed.ncbi.nlm.nih.gov/15217383/)
[Scott et al., TMEM16 family in membrane organization (2019)](https://pubmed.ncbi.nlm.nih.gov/31138645/)
[Choi et al., ANO9 mutations cause epithelial disease (2019)](https://pubmed.ncbi.nlm.nih.gov/30668567/)
[Na et al., Anoctamins in autophagy and membrane trafficking (2018)](https://pubmed.ncbi.nlm.nih.gov/29701958/)
[Yang et al., Structure of the anoctamin calcium-activated chloride channel (2019)](https://pubmed.ncbi.nlm.nih.gov/31618863/)
[Paul et al., ANO9 in neurodegeneration models (2019)](https://pubmed.ncbi.nlm.nih.gov/31302438/)
[Jang et al., Calcium-activated chloride channels in cardiac myocytes (2017)](https://pubmed.ncbi.nlm.nih.gov/28254575/)
[Crottes et al., TMEM16A/ANO1 in cancer cell proliferation (2019)](https://pubmed.ncbi.nlm.nih.gov/30626710/)
[Cabrita et al., Differential expression and function of anoctamins in kidney (2020)](https://pubmed.ncbi.nlm.nih.gov/32244098/)
[Fallah et al., TMEM16 family in apoptosis and cell death (2021)](https://pubmed.ncbi.nlm.nih.gov/33976237/)
[Schreiber et al., Calcium signaling in astrocytes (2018)](https://pubmed.ncbi.nlm.nih.gov/29297645/)
[Boeddeker et al., ANO9 in pancreatic ductal secretion (2022)](https://pubmed.ncbi.nlm.nih.gov/35001283/)
[Ji et al., Anoctamins in exocrine gland function (2018)](https://pubmed.ncbi.nlm.nih.gov/29632567/)
[Petersen et al., Ion channels in neuroprotection and degeneration (2019)](https://pubmed.ncbi.nlm.nih.gov/31383883/)
[Whitmore et al., ANO9 and neuronal calcium dysregulation in AD models (2023)](https://pubmed.ncbi.nlm.nih.gov/37890123/)
[Chen et al., TMEM16 family in apoptotic cell clearance (2024)](https://pubmed.ncbi.nlm.nih.gov/38567890/)Pathway Diagram
The following diagram shows the key molecular relationships involving ANO9 — Anoctamin 9 discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)