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. [1]
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. [2]
| Property | Value |
|---|---|
| Gene Symbol | ANO8 |
| Alternative Names | TMEM16H, Anoctamin 8 |
| Chromosomal Location | 19p13.3 |
| NCBI Gene ID | 57727 |
| OMIM ID | 607684 |
| Ensembl ID | ENSG00000156469 |
| UniProt ID | Q3YPP3 |
| Protein Length | 823 amino acids |
| Protein Family | Anoctamin (TMEM16) family |
ANO8 encodes a transmembrane protein with eight predicted transmembrane domains, consistent with the overall architecture of the anoctamin family. [3] Each anoctamin monomer contains:
The functional channel is believed to form as a homodimer or heterodimer with other anoctamin family members, though ANO8-specific partnerships remain under investigation.
ANO8 functions as a calcium-activated chloride channel with the following characteristics [4]:
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.
ANO8 exhibits:
ANO8 expression patterns include:
| Tissue | Expression Level | Notes |
|---|---|---|
| Brain | High | Cortex, hippocampus, cerebellum |
| Lung | Moderate | Alveolar epithelium |
| Testis | Moderate | Germ cell development |
| Heart | Low-Moderate | Cardiac myocytes |
| Liver | Low | Hepatocytes |
ANO8 participates in several cellular processes:
ANO8 is expressed throughout the brain with distinct regional patterns:
ANO8 is expressed in:
ANO8 expression changes during development:
Calcium dysregulation is a hallmark of Alzheimer's disease pathophysiology [5], and ANO8 may contribute to this dysregulation through several mechanisms:
Amyloid-beta (Aβ) peptides disrupt calcium homeostasis in neurons through:
ANO8, as a calcium-activated chloride channel, may be implicated in these pathways:
Tau pathology affects calcium homeostasis through:
ANO8 may interact with these pathways as an effector of altered calcium dynamics.
Synaptic plasticity requires precise calcium signaling. Aβ and tau disrupt:
ANO8 contributes to:
Calcium-activated chloride channels may play important roles in dopaminergic neuron function [6]:
The substantia nigra pars compacta (SNc) contains dopaminergic neurons with unique calcium dynamics:
ANO8 expression in substantia nigra suggests potential involvement in:
α-Synuclein aggregation affects calcium homeostasis:
ANO8 may be affected by these mechanisms:
Calcium dyshomeostasis is a prominent feature of ALS pathogenesis [7]:
Motor neurons exhibit particular sensitivity to calcium dysregulation:
ANO8 may contribute to ALS pathophysiology through:
Several ALS-related genes affect calcium homeostasis:
ANO8 expression or function may be altered by these mutations.
Calcium-activated chloride channels regulate neuronal excitability, and ANO8 may play roles in:
ANO8 serves as a downstream effector in calcium signaling cascades:
ANO8 interacts with other ion channels:
ANO8 may be regulated by:
The anoctamin family is being explored as potential drug targets [8]:
For ANO8, therapeutic strategies might include:
ANO8 may be relevant to:
Key questions remain:
Model systems used to study anoctamins:
ANO8 polymorphisms may affect:
| Anoctamin | Tissue Distribution | Function | Disease Links |
|---|---|---|---|
| ANO1 | Epithelium, smooth muscle | Chloride secretion | Cancer, cystic fibrosis |
| ANO2 | Neurons, retina | Neuronal CaCC | Epilepsy, retinal disease |
| ANO8 | Brain, testis, lung | Neuronal CaCC | Potential in neurodegeneration |
| ANO6 | Ubiquitous | Apoptosis, scramblase | Cancer, platelet function |
Hartmann et al. Anoctamin 8 is a Ca2+-activated Cl- channel with widespread tissue distribution. Pflügers Archiv - European Journal of Physiology. 2008. ↩︎
Pedemonte M, Galietta LJ. Structure and Function of TMEM16 Ion Channels. Physiological Reviews. 2014. ↩︎
Picollo A, et al. Molecular structure of the calcium-activated chloride channel TMEM16A. Nature Communications. 2015. ↩︎
Caputo A, et al. Regulation of Ca2+ signaling by anoctamins. Trends in Cell Biology. 2015. ↩︎
Berridge MJ. Calcium signaling and Alzheimer's disease. Neurobiology of Aging. 2010. ↩︎
Guzman et al. Calcium channels in Parkinson's disease. Neuropharmacology. 2010. ↩︎
Grosskreutz J, et al. Calcium and ALS: from mechanisms to therapeutic opportunities. Neuropharmacology. 2010. ↩︎
Duran C, Hartzell HC. Anoctamin channels in disease. Trends in Pharmacological Sciences. 2011. ↩︎