Phosphorylated Tau at Threonine 231 (p-tau231)

Overview

Phosphorylated Tau at Threonine 231 (p-tau231) is a hyperphosphorylated form of the Tau protein encoded by the MAPT gene. Phosphorylation at T231 represents an early and critical event in tau pathogenesis, making p-tau231 one of the most sensitive biomarkers for Alzheimer’s disease and other tauopathies^{1p-tau231 as an early biomarker for Alzheimer's disease2020 · DOI 10.1016/j.jad.2020.12.092Open reference}.

Biological Significance

Why Threonine 231?

The T231 phosphorylation site is particularly important because:

1. Early Marker: Phosphorylation occurs early in AD progression, even before clinical symptoms

2. Conformational Change: T231 phosphorylation promotes tau dimerization and oligomerization

3. Microtubule Disruption: Severely impairs tau’s ability to stabilize microtubules

4. Aggregation Nucleation: Serves as a seed for neurofibrillary tangle formation

Structural Context

T231 is located in the:

• Proline-rich domain (PRR): Residues 151-244

• Adjacent to microtubule-binding repeats (R1-R4)

• Critical hinge region between N-terminal and C-terminal domains

Phosphorylation Biology

Kinases

Multiple kinases phosphorylate T231:

Kinase	Role	Notes
GSK-3β	Primary	Hyperactive in AD brain
CDK5	Major	Phosphorylates T231 efficiently
MARK/PAR-1	Early event	Involved in tau spreading

Phosphatases

• PP2A: Major phosphatase dephosphorylating T231

• PP1: Minor contribution

• Activity reduced in AD brain

Role in Alzheimer’s Disease

Pathogenic Mechanisms

1. Microtubule Destabilization

   • Reduced tau-microtubule binding

   • Impaired axonal transport

   • Synaptic dysfunction

2. Tau Aggregation

   • p-tau231 promotes paired helical filament formation

   • Serves as template for further phosphorylation

   • Spreads between connected neurons

3. Neuronal Dysfunction

   • Loss of neurotrophic support

   • Mitochondrial transport defects

   • Calcium dysregulation

Spreading Mechanism

p-tau231 serves as a “seed” for prion-like propagation:

• Released from dying neurons

• Taken up by neighboring cells

• Templates further tau pathology

Biomarker Potential

Diagnostic Value

p-tau231 is an early and specific biomarker for AD:

Feature	p-tau231	p-tau181	p-tau217
Detectable in preclinical AD	++	+	+
Specificity for AD vs. other dementias	+++	++	+++
Correlation with tau PET	++	++	+++
Cerebrospinal fluid	Available	Available	Available
Blood-based detection	Emerging	Available	Emerging

Clinical Applications

• Early Diagnosis: Detectable before clinical symptoms

• Disease Progression: Correlates with cognitive decline

• Treatment Monitoring: Potential biomarker for drug trials

Detection Methods

Established Techniques

• ELISA: Highly sensitive CSF detection

• SIMOA: Ultra-sensitive blood detection

• Western Blot: Semi-quantitative analysis

• Mass Spectrometry: Site-specific quantification

Emerging Technologies

• Single molecule array (Simoa): Picoliter-scale detection

• Immuno-PCR: Enhanced sensitivity

• Blood p-tau231: Under development

Therapeutic Implications

Targeting p-tau231

1. Kinase Inhibitors: GSK-3β, CDK5 modulators

2. Phosphatase Activators: PP2A activators

3. Anti-tau Antibodies: Immunotherapy targeting phosphorylated tau

4. Aggregation Inhibitors: Prevent p-tau231 oligomerization

Challenges

• Blood-brain barrier penetration

• Kinase inhibitor specificity

• Early intervention timing

Research Directions

• Blood-based p-tau231 detection

• PET ligands for p-tau231

• Understanding kinase-phosphatase balance

• Clinical validation studies

See Also

• Alzheimer’s Disease

• Tau Protein

• MAPT Gene

• p-tau181

• p-tau217

• Neurofibrillary Tangles

• Tau Pathology

External Links

• UniProt: P10636

• AlphaFold: P10636

• AlzGene: MAPT