RESUMEN
The Microtubule-binding repeat region (MTBR) of Tau has been studied extensively due to its pathological implications in neurodegenerative diseases like Alzheimer's disease. The pathological property of MTBR is mainly due to the R3 repeat's high propensity for self-aggregation, highlighting the critical molecular grammar of the repeat. Utilizing the R1R3 construct (WT) and its G326E mutant (EE), we determine the distinct characteristics of various peptide segments that modulate the aggregation propensity of the R3 repeat using NMR spectroscopy. Through time-dependent experiments, we have identified 317KVTSKCGS324 in R3 repeat as the aggregation initiating motif (AIM) due to its role at the initial stages of aggregation. The G326E mutation induces changes in conformation and dynamics at the AIM, thereby effectively abrogating the aggregation propensity of the R1R3 construct. We further corroborate our findings through MD simulations and propose that AIM is a robust site of interest for tauopathy drug design.
Asunto(s)
Simulación de Dinámica Molecular , Agregado de Proteínas , Proteínas tau , Proteínas tau/química , Proteínas tau/metabolismo , Proteínas tau/genética , Humanos , Resonancia Magnética Nuclear Biomolecular , Mutación , Secuencia de AminoácidosRESUMEN
The initial stages of amyloid fibrilization begin with the monomers populating aggregation-prone conformers. Characterization of such aggregation-prone conformers is crucial in the study of neurodegenerative diseases. The current study characterizes the aggregation pathway of two tau protein constructs that have been recently demonstrated to form Alzheimer's (AD) fibril structures with divalent ions and chronic traumatic encephalopathy (CTE) fibril structures with monovalent ions. The results highlight the involvement of identical residues in both the primary and secondary processes of both AD and CTE fibril propagation. Nuclear magnetic resonance relaxation experiments reveal increased flexibility of the motifs 321KCGS within R3 and 364PGGGN within R4 in the presence of MgCl2/NaCl, correlating with faster aggregation kinetics and indicating efficient primary nucleation. Notably, the seeded aggregation kinetics of the tau monomers in the presence and absence of metal ions are strikingly different. This correlates with the overall sign of the 15N-ΔR2 profile specifying the dominant mechanism involved in the process of aggregation.