Heterogeneous Tau-Tubulin Complexes Accelerate Microtubule Polymerization

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Tau protein stabilizes neuronal microtubules, crucial for cellular function.
• The precise mechanism of tau-tubulin interaction and its role in neurodegeneration remain unclear.
• Understanding tau's interaction with soluble tubulin is vital for both normal function and disease pathology.

Purpose of the Study:

• To investigate the relationship between tau-tubulin complex heterogeneity and tau's function.
• To elucidate the structural contributions to tau-tubulin complex formation.
• To correlate complex characteristics with tau's effect on microtubule polymerization.

Main Methods:

• Creation of truncated and scrambled tau constructs.
• Characterization of tau-tubulin complex size and heterogeneity under non-polymerizing conditions.
• Assessment of construct function using tubulin polymerization assays.

Main Results:

• The pseudo-repeat region of tau is a major contributor to large, heterogeneous tau-tubulin complexes.
• Additional tubulin binding sites were identified within repeats two and three of the microtubule-binding domain.
• A positive correlation exists between complex size/heterogeneity and the rate of tau-promoted microtubule polymerization.

Conclusions:

• Tau-tubulin complexes can be described as "fuzzy" complexes, highlighting dynamic interactions.
• Heterogeneous complex formation is critical for tau's microtubule-stabilizing function.
• This study provides fundamental insights into intrinsically disordered protein function, emphasizing dynamic complex relevance.