ANO8 (Anoctamin 8)

ANO8 (Anoctamin 8)

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">ANO8 (Anoctamin 8)</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>ANO8</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>TMEM16H, Anoctamin 8</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>19p13.3</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>57727</td>
</tr>
<tr>
<td class="label">OMIM ID</td>
<td>607684</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000156469</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q3YPP3</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>823 amino acids</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Anoctamin (TMEM16) family</td>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>High</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Testis</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Low-Moderate</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Anoctamin</td>
<td>Tissue Distribution</td>
</tr>
<tr>
<td class="label">ANO1</td>
<td>Epithelium, smooth muscle</td>
</tr>
<tr>
<td class="label">ANO2</td>
<td>Neurons, retina</td>
</tr>
<tr>

ANO8 (Anoctamin 8)

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">ANO8 (Anoctamin 8)</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>ANO8</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>TMEM16H, Anoctamin 8</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>19p13.3</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>57727</td>
</tr>
<tr>
<td class="label">OMIM ID</td>
<td>607684</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000156469</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q3YPP3</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>823 amino acids</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Anoctamin (TMEM16) family</td>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>High</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Testis</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Low-Moderate</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Anoctamin</td>
<td>Tissue Distribution</td>
</tr>
<tr>
<td class="label">ANO1</td>
<td>Epithelium, smooth muscle</td>
</tr>
<tr>
<td class="label">ANO2</td>
<td>Neurons, retina</td>
</tr>
<tr>
<td class="label">ANO8</td>
<td>Brain, testis, lung</td>
</tr>
<tr>
<td class="label">ANO6</td>
<td>Ubiquitous</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

ANO8 (Anoctamin 8), also known as TMEM16H (Transmembrane Protein 16H), is a member of the anoctamin family of calcium-activated chloride channels (CaCCs). The anoctamin family comprises 10 members (ANO1-10) in humans, all of which function either as calcium-activated chloride channels or as phospholipid scramblases. ANO8 is expressed in various tissues including the brain, lung, testis, and cardiovascular system, with particularly notable expression in neuronal tissues where it participates in calcium-dependent signaling pathways relevant to neurodegenerative diseases. [@hartmann2008]

The anoctamin family has emerged as critical regulators of cellular ion homeostasis, with ANO8 representing a somewhat atypical member whose precise physiological roles are still being characterized. Unlike some well-studied family members like ANO1 (TMEM16A) which is prominent in epithelial secretion, ANO8 exhibits a more restricted tissue distribution with enriched expression in neuronal populations. This neuronal enrichment has sparked interest in understanding its potential contributions to neurodegenerative disease pathogenesis, particularly given the central role of calcium dysregulation in conditions like Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. [@pedemonte2014]

Gene Information

Protein Structure and Function

Structural Architecture

ANO8 encodes a transmembrane protein with eight predicted transmembrane domains, consistent with the overall architecture of the anoctamin family. [@picollo2015] Each anoctamin monomer contains:

• N-terminal cytoplasmic domain: Contains regulatory sequences
• Transmembrane segments 1-8: Form the ion conduction pathway
• Re-entrant loop: Forms part of the pore structure
• C-terminal cytoplasmic domain: Contains regulatory elements

Calcium Activation Mechanism

ANO8 functions as a calcium-activated chloride channel with the following characteristics [@caputo2015]:

The calcium sensitivity of ANO8 suggests it serves as a downstream effector of calcium signaling cascades, converting calcium signals into chloride conductance changes that modulate cellular excitability.

Ion Selectivity and Conductance

ANO8 exhibits:

• High chloride selectivity: Prefers Cl- over other anions
• Moderate conductance: Typical single-channel conductance in the range of 10-30 pS
• Voltage dependence: Mild voltage-dependent activation
• Calcium sensitivity: Sub-micromolar calcium affinity

Tissue-Specific Expression

ANO8 expression patterns include:

Cellular Functions

ANO8 participates in several cellular processes:

Expression Patterns in the Brain

Regional Distribution

ANO8 is expressed throughout the brain with distinct regional patterns:

• Cerebral [cortex](/brain-regions/cortex): High expression in pyramidal neurons
• [Hippocampus](/brain-regions/hippocampus): Prominent in CA1-CA3 regions and dentate gyrus
• Cerebellum: Purkinje cells and granule cells
• Substantia nigra: Dopaminergic neurons
• Basal ganglia: Medium spiny neurons
• Brainstem: Various neuronal populations

Cell Type Expression

ANO8 is expressed in:

• [Neurons](/entities/neurons): Both excitatory and inhibitory neurons
• [Astrocytes](/entities/astrocytes): Glial expression
• [Oligodendrocytes](/entities/oligodendrocytes): Myelin-producing cells
• Vascular endothelial cells: Blood-brain barrier

Developmental Expression

ANO8 expression changes during development:

• Low expression in embryonic brain
• Increasing expression postnatally
• Stable expression in adult brain
• Potential changes in aging

Neurodegeneration Connections

Alzheimer's Disease

Calcium dysregulation is a hallmark of Alzheimer's disease pathophysiology [@berridge2010], and ANO8 may contribute to this dysregulation through several mechanisms:

Amyloid-Beta Effects

[Amyloid-beta](/proteins/amyloid-beta) (Aβ) peptides disrupt calcium homeostasis in neurons through:

• Formation of calcium-permeable channels in membrane
• Activation of NMDA receptors leading to calcium overload
• Dysfunction of calcium ATPases and channels
• ER calcium release through ryanodine receptors

• Modulation of excitotoxicity: Chloride flux influences membrane potential and excitatory status
• Response to calcium overload: ANO8 activation may occur secondary to calcium dysregulation
• Contribution to chloride homeostasis: Disrupted chloride regulation affects GABAergic signaling

Tau Pathology Connections

[Tau](/proteins/tau) pathology affects calcium homeostasis through:

• Microtubule disruption affecting calcium channel trafficking
• Direct interaction with voltage-gated calcium channels
• Synaptic zinc dysregulation affecting calcium signaling

Synaptic Dysfunction

Synaptic plasticity requires precise calcium signaling. Aβ and tau disrupt:

• Long-term potentiation (LTP)
• Long-term depression (LTD)
• Calcium-dependent gene expression

• Resting chloride conductance affecting synaptic integration
• Calcium signal termination
• Voltage dynamics at synapses

Parkinson's Disease

Calcium-activated chloride channels may play important roles in dopaminergic neuron function [@guzman2010]:

Substantia Nigra Vulnerability

The substantia nigra pars compacta (SNc) contains dopaminergic neurons with unique calcium dynamics:

• Pacemaker activity requires L-type calcium channels
• Calcium influx during pacemaking creates metabolic stress
• Mitochondrial dysfunction results from calcium overload

• Modulating neuronal excitability
• Responding to calcium dysregulation
• Contributing to dopaminergic neuron vulnerability

Alpha-Synuclein Interactions

[α-Synuclein](/proteins/alpha-synuclein) aggregation affects calcium homeostasis:

• Forms ion-permeable membrane pores
• Disrupts mitochondrial calcium handling
• Activates ER stress pathways

• Calcium dysregulation could hyperactivate ANO8
• Chloride conductance changes affect excitability
• Potential for positive feedback on pathology

Amyotrophic Lateral Sclerosis (ALS)

Calcium dyshomeostasis is a prominent feature of ALS pathogenesis [@grosskreutz2010]:

Motor Neuron Vulnerability

Motor neurons exhibit particular sensitivity to calcium dysregulation:

• Low calcium-buffering capacity
• High mitochondrial demand
• Long axons requiring efficient calcium handling

• Modulation of motor neuron excitability
• Response to calcium dysregulation
• Potential interactions with ALS-related proteins

Relationships with ALS Genes

Several ALS-related genes affect calcium homeostasis:

• SOD1 mutations: Disrupt mitochondrial calcium handling
• TARDBP (TDP-43): Affects calcium channel expression
• FUS: Alters RNA processing of calcium-related genes
• C9orf72: Affects calcium signaling pathways

Epilepsy

Calcium-activated chloride channels regulate neuronal excitability, and ANO8 may play roles in:

• Seizure susceptibility
• Epileptogenesis
• Antiepileptic drug responses

Mechanism of Action

Calcium Signaling Integration

ANO8 serves as a downstream effector in calcium signaling cascades:

Interaction with Other Ion Channels

ANO8 interacts with other ion channels:

• Voltage-gated calcium channels: Source of activating calcium
• GABA-A receptors: Chloride conductance synergy
• KCC2: Chloride extrusion coordination
• Volume-regulated anion channels: Regulatory volume decrease

Signaling Pathways

ANO8 may be regulated by:

• Calmodulin: Calcium-dependent regulatory protein
• Phosphorylation: PKA, PKC modulation
• Trafficking: Surface expression regulation
• Alternative splicing: Functional variants

Therapeutic Implications

Drug Discovery Targets

The anoctamin family is being explored as potential drug targets [@duran2011]:

Agonists

• Increase chloride secretion: Potential for cystic fibrosis (ANO1)
• Modulate neuronal excitability: Potential for epilepsy

Antagonists

• Reduce pathological chloride flux: Cancer proliferation
• Modulate smooth muscle tone: Hypertension

ANO8-Specific Considerations

For ANO8, therapeutic strategies might include:

• Calcium homeostasis modulators: Address upstream calcium dysregulation
• ANO8 expression modulators: Reduce pathological expression
• Channel blockers: Prevent excessive chloride flux

Clinical Relevance

ANO8 may be relevant to:

• Biomarker development: ANO8 expression as disease marker
• Drug response prediction: ANO8 variants affecting therapy
• Gene therapy potential: Modulate ANO8 expression

Research Directions

Current Research Focus

Emerging Areas

• Single-cell sequencing: ANO8 expression in specific neuronal types
• iPSC models: Neurons from neurodegenerative disease patients
• CRISPR screens: ANO8 genetic interactions
• Structural biology: High-resolution ANO8 structure

Knowledge Gaps

Key questions remain:

• What are the precise physiological roles of ANO8?
• How does ANO8 contribute to neurodegenerative diseases?
• Can ANO8 be safely targeted therapeutically?
• What are the downstream effectors of ANO8 activity?

Animal Models

Model systems used to study anoctamins:

• Mouse models: Knockout and transgenic lines
• Zebrafish: Visualize channel function in vivo
• Xenopus oocytes: Electrophysiological characterization
• Cell lines: Overexpression and knockdown studies

Genetics and Variants

Known Variants

ANO8 polymorphisms may affect:

• Channel expression levels
• Calcium sensitivity
• Protein trafficking
• Disease susceptibility

Population Genetics

• ANO8 shows limited coding variation
• Common variants in regulatory regions
• Potential ancestry differences in allele frequencies

Comparison with Other Anoctamins

See Also

• [Calcium Signaling](/mechanisms/calcium-signaling)
• [Chloride Channels](/entities/chloride-channels)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [Neuronal Excitability](/mechanisms/neuronal-excitability)
• [Ion Channelopathies](/mechanisms/ion-channelopathies)
• [Neurodegeneration](/diseases/neurodegeneration)

External Links

• [NCBI Gene: ANO8](https://www.ncbi.nlm.nih.gov/gene/57727)
• [UniProt: ANO8](https://www.uniprot.org/uniprot/Q3YPP3)
• [GeneCards: ANO8](https://www.genecards.org/cgi-bin/carddisp.pl?gene=ANO8)
• [Ensembl: ANO8](https://www.ensembl.org/Homo_sapiens/ENSG00000156469)
• [HGNC: ANO8](https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/49968)

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