| Property | Value |
|---|---|
| Protein Name | Choline Acetyltransferase |
| Gene | CHAT |
| UniProt ID | P21908 |
| Molecular Weight | ~82 kDa (human) |
| Subcellular Localization | Cytoplasm of cholinergic neurons |
| Protein Family | Carnitine/choline acetyltransferase family |
| Tissue Expression | Cholinergic neurons (brain, spinal cord, periphery) |
Choline acetyltransferase (CHAT) is the enzyme that synthesizes the neurotransmitter acetylcholine (ACh) from choline and acetyl-CoA[1]. It is the definitive marker for cholinergic neurons—cells that use acetylcholine as their primary neurotransmitter. CHAT is essential for cholinergic signaling throughout the nervous system, including in brain regions critical for memory and attention (basal forebrain), motor control (brainstem and spinal cord), and autonomic function.
The cholinergic system is prominently affected in Alzheimer's disease, where CHAT activity is dramatically reduced in the basal forebrain and cortex. This loss underlies the cognitive deficits characteristic of AD and has driven the development of cholinesterase inhibitor drugs (donepezil, rivastigmine, galantamine) as symptomatic treatments[2].
CHAT has a characteristic enzyme architecture[1:1]:
The enzyme is organized as a homodimer, with each subunit containing distinct substrate-binding sites for choline and acetyl-CoA.
CHAT catalyzes a simple transfer reaction:
Choline + Acetyl-CoA → Acetylcholine + CoA
The reaction proceeds through a ternary complex mechanism:
CHAT activity is regulated at multiple levels:
| Regulatory Mechanism | Effect |
|---|---|
| Transcriptional control | Cell-type specific expression |
| Alternative splicing | Multiple isoforms with different properties |
| Post-translational modification | Phosphorylation affects activity |
| Product inhibition | Acetylcholine feedback |
CHAT is the sole enzyme for ACh biosynthesis:
CHAT defines the cholinergic system:
Different CHAT isoforms are expressed in:
CHAT loss is a hallmark of AD pathophysiology[2:1]:
Cholinergic Degeneration:
Pathogenic Mechanisms:
Diagnostic Significance:
CHAT alterations in PD include:
| Disorder | CHAT Involvement |
|---|---|
| DLB | Severe cholinergic loss |
| MCI | Early cholinergic changes |
| Myasthenia gravis | Autoantibodies affect function |
| ALS | Motor neuron cholinergic changes |
Cholinesterase inhibitors are standard AD therapy[3]:
| Drug | Mechanism | Status |
|---|---|---|
| Donepezil | AChE inhibition | Approved |
| Rivastigmine | AChE/BChE inhibition | Approved |
| Galantamine | AChE modulation | Approved |
These drugs increase synaptic acetylcholine by inhibiting its breakdown, partially compensating for CHAT loss.
| Strategy | Approach | Status |
|---|---|---|
| CHAT gene therapy | Restore CHAT expression | Preclinical |
| Acetylcholine receptor agonists | Direct receptor activation | Various |
| Neurotrophic factors | Support cholinergic neurons | Research |
CHAT-related biomarkers:
Misawa H, et al. Choline acetyltransferase and acetylcholine. Journal of Neurochemistry. 2011. ↩︎ ↩︎
O'Brien M, et al. Cholinergic neurons in AD and cholinergic therapies. Nature Reviews Neurology. 2023. ↩︎ ↩︎
Hampel H, et al. Cholinergic system: emerging targets for AD therapy. Drug Discovery Today. 2018. ↩︎