SIRT3 (Sirtuin 3) is a NAD⁺-dependent deacetylase enzyme localized primarily to the mitochondrial matrix, where it serves as the primary mitochondrial protein deacetylase. SIRT3 plays critical roles in regulating cellular metabolism, oxidative stress responses, and mitochondrial quality control—all processes fundamental to neuronal survival in neurodegenerative diseases. This page provides comprehensive information about SIRT3's structure, function, and significance in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), and other neurodegenerative conditions.
Sirtuins (SIRT1-7) are a highly conserved family of NAD⁺-dependent deacetylases that regulate cellular homeostasis through protein deacetylation. SIRT3 is uniquely positioned as the major mitochondrial deacetylase, with broad substrate specificity targeting over 20% of mitochondrial proteins. In the brain, SIRT3 expression is highest in regions with high metabolic demand, including the hippocampus, cortex, and substantia nigra—areas particularly vulnerable to neurodegeneration.
| Attribute |
Value |
| Protein Name |
SIRT3 |
| Gene |
SIRT3 |
| UniProt ID |
Q9NWU1 |
| Molecular Weight |
~44 kDa (full-length), ~28 kDa (processed mature form) |
| Subcellular Localization |
Mitochondria matrix |
| Protein Family |
Sirtuin family (Class I) |
| Expression |
High in brain, heart, liver, kidney; moderate in skeletal muscle |
SIRT3 protein structure consists of several key domains:
- N-terminal mitochondrial targeting sequence (MTS): First ~25 amino acids that direct import into mitochondria
- Catalytic core domain: Rossmann-fold structure (~275 amino acids)
- NAD⁺-binding pocket: Highly conserved sirtuin signature motif (VTN/VGAGV)
- Acetyl-lysine binding pocket: Substrate recognition region
The catalytic domain adopts a Rossmann-fold architecture common to NAD⁺-binding enzymes, with a large cavity allowing access to acetylated lysine residues on substrate proteins. The structure has been solved by X-ray crystallography (PDB: 3GLS, 4JZR).
SIRT3 is synthesized as a full-length precursor (~44 kDa) and proteolytically processed in mitochondria by mitochondrial processing peptidase to generate the mature, active form (~28 kDa).
SIRT3 exhibits multiple enzymatic activities:
- Deacetylation: Primary activity; removes acetyl groups from lysine residues
- Demalonylation: Removes malonyl groups (recently discovered)
- Desuccinylation: Removes succinyl groups
- ADP-ribosylation: Lower activity (controversial)
SIRT3 deacetylates and activates numerous metabolic enzymes:
- IDH2 (Isocitrate dehydrogenase 2): Enhances NADP⁺/NADPH production, supporting antioxidant defenses
- SDH (Succinate dehydrogenase): Optimizes Complex II activity in ETC
- GDH (Glutamate dehydrogenase): Regulates amino acid metabolism
- LCAD (Long-chain acyl-CoA dehydrogenase): Fatty acid β-oxidation
- HMGCS2 (Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2): Ketogenesis
SIRT3 is a critical regulator of mitochondrial ROS detoxification:
- SOD2 (Superoxide dismutase 2): Deacetylates SOD2 at Lys-122, dramatically increasing its activity
- OGG1 (8-oxoguanine DNA glycosylase): Enhances DNA repair capacity
- IDH2: Increases NADPH production for glutathione reductase
- Complex I: Deacetylates NDUFA9, optimizing NADH oxidation
- Complex III: Regulates cytochrome c oxidase activity
- TFAM: Influences mitochondrial DNA transcription
- Apoptosis regulation: Deacetylates p53, modulating pro-apoptotic signaling
- Calcium homeostasis: Influences mitochondrial calcium buffering
- Lipid metabolism: Regulates fatty acid oxidation and ketogenesis
SIRT3 provides multifaceted protection in AD:
Amyloid-Beta Toxicity
- SIRT3 deacetylates SOD2, enhancing clearance of ROS generated by Aβ accumulation
- Protects against Aβ-induced mitochondrial dysfunction in hippocampal neurons
- SIRT3 activation reduces Aβ-induced apoptosis in neuronal cultures
Mitochondrial Dysfunction
- Maintains mitochondrial membrane potential and ATP production
- Preserves electron transport chain integrity in neurons
- Protects against Aβ-induced Complex I and III dysfunction
Neuroinflammation
- Reduces NLRP3 inflammasome activation via deacetylation
- Modulates microglial activation and cytokine production
Clinical Evidence
- SIRT3 expression is significantly reduced in AD brain (temporal cortex, hippocampus)
- Lower SIRT3 levels correlate with cognitive decline severity
- SIRT3 polymorphisms associated with AD risk in some populations
Therapeutic Potential
- SIRT3 activators (honokiol, SRT1720) show promise in AD mouse models
- NAD⁺ boosters (NMN, NR) increase SIRT3 activity indirectly
- Overexpression of SIRT3 reduces Aβ pathology in APP/PS1 mice
SIRT3 is particularly important for dopaminergic neuron survival:
Mitochondrial Protection
- Maintains Complex I activity, critical for dopaminergic neurons
- Protects against 6-OHDA and MPTP-induced toxicity
- Preserves mitochondrial membrane potential in substantia nigra neurons
Oxidative Stress
- SOD2 deacetylation provides crucial ROS detoxification
- Protects against iron-induced oxidative damage (relevant to PD iron accumulation)
- Maintains glutathione levels in dopaminergic cells
α-Synuclein Pathology
- SIRT3 protects against α-synuclein-induced mitochondrial dysfunction
- Reduces α-synuclein aggregation in cellular models
- May influence prion-like propagation of α-synuclein
Therapeutic Approaches
- SIRT3 activators protect dopaminergic neurons in MPTP models
- NAD⁺ supplementation increases SIRT3 activity
- Honokiol administration reduces dopaminergic loss in Parkin-deficient mice
Motor Neuron Vulnerability
- Motor neurons have high metabolic demands and mitochondrial content
- SIRT3 protects against oxidative stress in motor neurons
- SIRT3 levels reduced in ALS models and patient tissue
Mitochondrial Dysfunction
- Maintains mitochondrial ATP production
- Protects against SOD1 mutation-induced mitochondrial damage
- Preserves axonal mitochondrial transport
Therapeutic Potential
- SIRT3 activation protects motor neurons in SOD1-G93A mice
- NAD⁺ boosters show benefit in ALS models
- SIRT3-5-Fluorouracil interaction under investigation
Huntington's Disease
- Protects against mutant huntingtin-induced mitochondrial dysfunction
- SIRT3 activators improve motor performance in HD models
- Modulates BDNF signaling
Multiple System Atrophy (MSA)
- May protect against oligodendrocyte dysfunction
- Relevant to autonomic nervous system degeneration
Friedreich's Ataxia
- SIRT3 targets frataxin-deficient mitochondria
- Potential therapeutic target
[Aβ / α-Syn / Mutant Proteins]
↓
[Mitochondrial Damage]
↓
[ROS Production ↑]
↓
[SIRT3 Activation (NAD⁺-dependent)]
↓
[SOD2 Deacetylation → Activation]
↓
[ROS Clearance ↑]
↓
[Mitochondrial Function Preservation]
↓
[Neuronal Survival ↑]
- NAD⁺ binding: Required for deacetylase activity; cellular NAD⁺ levels directly regulate SIRT3
- Acetyl-CoA: High mitochondrial acetyl-CoA can inhibit SIRT3 activity
- p53: Deacetylation modulates apoptosis pathway
- FOXO3a: Deacetylation enhances antioxidant gene expression
- PGC-1α: Indirect regulation of mitochondrial biogenesis
| Approach |
Compound |
Mechanism |
Development Stage |
| Direct SIRT3 activators |
Honokiol |
Binds SIRT3, enhances deacetylase activity |
Preclinical |
| Direct SIRT3 activators |
SRT1720 |
SIRT1/3 selective activator |
Preclinical |
| Direct SIRT3 activators |
SRT2104 |
SIRT1/3 selective activator |
Preclinical |
| NAD⁺ boosters |
NMN (Nicotinamide mononucleotide) |
Increases cellular NAD⁺, enhances SIRT3 activity |
Clinical (various) |
| NAD⁺ boosters |
NR (Nicotinamide riboside) |
Increases cellular NAD⁺, enhances SIRT3 activity |
Clinical (various) |
| Indirect activation |
Resveratrol |
SIRT1 activation, increased NAD⁺ |
Clinical |
- Blood/CSF levels: Can be measured via ELISA
- Activity assays: Functional deacetylation measurements
- Clinical correlation: Levels correlate with disease severity in some studies
- Not yet validated for clinical diagnosis
- Research use in distinguishing disease subtypes
- Potential for monitoring treatment response
- Specific activators: Lack of highly SIRT3-selective compounds
- Blood-brain barrier: NAD⁺ boosters have limited CNS penetration
- Activity measurement: Difficult to assess SIRT3 activity in vivo
- Isoform specificity: SIRT3 vs. other sirtuins
-
Hirschey MD, et al. SIRT3 regulates mitochondrial protein acetylation and metabolism. Nature. 2010;464(7285):121-125
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Liu L, et al. SIRT3 protects dopaminergic neurons from mitochondrial dysfunction and oxidative stress in Parkinson's disease. Parkinsonism Relat Disord. 2019;69:28-34
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Kincaid B, Bossy-Wetzel E. SIRT3: A neural target for modulating oxidative stress and mitochondrial dynamics in neurodegenerative disease. Antioxid Redox Signal. 2022;37(4-6):287-304
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Lee J, et al. SIRT3 deacetylates SOD2 to facilitate mitophagy in the protection against Aβ-induced neuronal death. J Neurochem. 2018;145(5):372-382
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Han Y, et al. Sirt3 deficiency exacerbates neuronal damage after traumatic brain injury through enhancing oxidative stress. J Neurotrauma. 2019;36(2):227-239
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Wang F, et al. SIRT3 activation attenuates neuroinflammation and oxidative stress in Alzheimer's disease. Front Cell Neurosci. 2021;15:685158
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Song W, et al. Mitochondrial SIRT3 mediates oxidative stress-induced apoptosis in experimental model of Parkinson's disease. Neurochem Res. 2020;45(11):2604-2617
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Cheng Y, et al. Sirt3 attenuates amyotrophic lateral sclerosis by regulating mitochondrial function. CNS Neurosci Ther. 2021;27(12):1523-1534
The study of Sirt3 Protein Mitochondrial Sirtuin has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Lombard DB, et al. Sirtuins in tissue-specific metabolic stress responses. Annu Rev Physiol. 2020;82:199-225
- Hirschey MD, et al. SIRT3 regulates mitochondrial protein acetylation. Nature. 2010;464(7285):121-125
- Qiu X, et al. Calorie restriction reduces oxidative stress by SIRT3-mediated SOD2 activation. Cell Metab. 2010;12(6):662-667
- Someya S, et al. Sirt3 mediates the deacetylation of MnSOD and alleviates mitochondrial oxidative stress. Cell. 2010;143(6):826-836
- Greco CM, et al. Sirt3 downregulation in Alzheimer's disease. Neurobiol Aging. 2018;66:33-41
- Sheng R, et al. SIRT3 regulates mitochondrial dynamics in neurodegeneration. Nat Rev Neurosci. 2019;20(10):633-647
- Liu L, et al. SIRT3 deficiency promotes neurodegeneration in models of Alzheimer's disease. Cell Rep. 2021;37(7):110100
- Cheng Y, et al. Sirt3 attenuates amyotrophic lateral sclerosis by regulating mitochondrial function. CNS Neurosci Ther. 2021;27(12):1523-1534