| ATP1A2 Protein |
|---|
| Protein Name | Na+/K+-ATPase Alpha 2 Subunit |
| Gene | [ATP1A2](/genes/atp1a2) |
| UniProt ID | [P50991](https://www.uniprot.org/uniprot/P50991) |
| PDB ID | 3wgu, 5aw0 |
| Molecular Weight | ~112 kDa |
| Subcellular Localization | Cell membrane (plasma membrane) |
| Protein Family | P-type ATPase family |
| Expression | Skeletal muscle, heart, brain ([neurons](/entities/neurons), astrocytes) |
The Na+/K+-ATPase alpha 2 subunit (ATP1A2) is a catalytic subunit of the sodium-potassium pump, a fundamental membrane protein that maintains the electrochemical gradients essential for neuronal excitability, secondary transport, and cellular homeostasis. Mutations in ATP1A2 cause familial hemiplegic migraine type 2 (FHM2) and are implicated in Alzheimer's disease and other neurological disorders.[1]
ATP1A2 is a P-type ATPase with characteristic architecture:
¶ Transmembrane Domain
- 10 transmembrane segments (M1-M10)
- Ion binding sites located within the transmembrane domain
- Conformational changes drive ion translocation
- Large cytosolic loop (between M4-M5): Contains ATP binding and phosphorylation domains
- Actuator domain (A domain): Between M2-M3
- Phosphorylation domain (P domain): Contains the invariant Asp residue for ATP-dependent phosphorylation
The enzyme has three binding sites for Na+ (on the intracellular side) and two for K+ (on the extracellular side). The binding sites involve conserved aspartate residues in transmembrane segments M4, M5, and M6.
The Na+/K+-ATPase maintains the characteristic ion gradients across the plasma membrane:
- 3 Na+ ions exported per cycle (out of the cell)
- 2 K+ ions imported into the cell
- ATP hydrolysis provides the energy (E1-E2 conformational cycle)
The pump contributes approximately -10 mV to the resting membrane potential and is crucial for:
- Maintaining neuronal excitability
- Setting the gradient for secondary transporters
- Regulating cell volume
The Na+ gradient drives numerous secondary transporters:
- Glutamate transporters: EAATs use Na+ gradients for glutamate uptake
- Glucose transporters: SGLT family
- Calcium exchangers: NCX relies on Na+ gradient
- Neurotransmitter transporters: DAT, SERT, NET
By maintaining low intracellular Na+, ATP1A2 indirectly supports:
- NCX (Na+/Ca2+ exchanger) function
- Calcium clearance from neurons
- Prevention of calcium overload
In astrocytes, ATP1A2 is particularly important for:
- Potassium spatial buffering
- Glutamate uptake maintenance
- Astrocyte-neuron metabolic coupling
FHM2 is caused by heterozygous mutations in ATP1A2, typically loss-of-function variants:[2]
- Severe migraine attacks with temporary paralysis on one side of the body (hemiplegia)
- Aura symptoms: visual, sensory, or motor
- Triggered by stress, fatigue, or certain foods
- Onset typically in adolescence or early adulthood
- ~50-75% reduction in Na+/K+ pump activity
- Impaired glutamate clearance due to reduced Na+ gradient
- Cortical spreading depression susceptibility
- Elevated extracellular K+ during neural activity
Over 30 pathogenic mutations identified, including:
- D999N: Common mutation with severe phenotype
- T345A: Reduced Na+ affinity
- W281R: Complete loss of function
ATP1A2 dysfunction is implicated in AD through multiple mechanisms:
- Na+/K+ ATPase activity significantly reduced in AD brains[3]
- Correlates with disease severity
- May precede other pathological changes
- Calcium dysregulation: Impaired NCX function
- Glutamate toxicity: Reduced EAAT activity
- Energy failure: Impaired secondary transport
- Amyloid effects: Aβ directly inhibits ATP1A2[4]
ATP1A2 alterations in PD include:
- Reduced expression in substantia nigra
- May contribute to neuronal vulnerability
- Interactions with alpha-synuclein
- Migraine without hemiplegia: Some ATP1A2 variants
- Epilepsy: Several mutations associated with seizure disorders
- Alternating hemiplegia of childhood: Related channelopathies
- Acetazolamide: Carbonic anhydrase inhibitor used prophylactically
- Veratran (channel blocker): Being investigated for FHM
- Gene therapy approaches: Under development
- Na+/K+ ATPase activators: Being investigated for AD
- Lifestyle interventions: Ketogenic diet may improve pump function
- Potassium channel modulators: Target compensatory mechanisms
ATP1A2 activity in:
- CSF: Potential biomarker for neuronal dysfunction
- Platelets: Reflects peripheral nervous system function
- De Fusco et al., Nat Genet (2003): ATP1A2 mutations cause FHM2
- Bottger et al., EMBO J (2011): Structure of Na+/K+-ATPase
- Dick et al., J Cereb Blood Flow Metab (2009): ATP1A2 in migraine pathogenesis
- Berlett & O'Neill, J Alzheimer's Dis (2010): Na+/K+ ATPase in AD
- Guatteo et al., J Neurosci Res (2005): ATP1A2 and glutamate transport
[1] Na+/K+-ATPase in neurological disease (2019)
[2] Familial hemiplegic migraine type 2: Genetics and pathogenesis (2015)
[3] Na+/K+ ATPase in Alzheimer's disease brain (2010)
[4] Amyloid-beta inhibits Na+/K+ ATPase (2008)
[5] Astrocyte Na+/K+ ATPase in neurodegeneration (2019)