Capturing Early Aggregation Transitions of Disordered Tau by Covalent Footprinting Mass Spectrometry

Area of Science:

• Biochemistry
• Neuroscience
• Structural Biology

Background:

• Tau aggregation into beta-sheet-rich fibrils is a hallmark of Alzheimer's disease.
• Early conformational changes in tau are critical for understanding aggregation but remain poorly understood.
• Intrinsically disordered proteins like tau present technical challenges for structural analysis.

Purpose of the Study:

• To capture dynamic conformational changes in full-length human tau during aggregation.
• To identify early molecular events in tau aggregation using a novel technique.
• To provide insights into Alzheimer's disease pathogenesis and therapeutic strategies.

Main Methods:

• Utilized diethyl pyrocarbonate (DEPC) covalent footprinting on full-length human tau 2N4R.
• Combined DEPC footprinting with proteolytic digestion for extensive sequence coverage.
• Employed mass spectrometry to analyze peptide-level kinetics and residue-level changes.

Main Results:

• Captured dynamic conformational transitions across tau during a 72-hour aggregation process.
• Identified the microtubule-binding domain (MTBD) as exhibiting the most significant structural changes.
• Observed early nucleation events and progressive fibril maturation, with N-terminal and C-terminal regions remaining solvent-exposed.

Conclusions:

• Mass spectrometry-based covalent footprinting can directly observe early, dynamic conformational transitions in tau.
• This technique complements existing methods that primarily resolve mature aggregated states.
• Understanding these early changes is crucial for developing effective Alzheimer's disease therapeutics.