Irina Ritsch: Transthyretin aggregation in fluid flow- a structural perspective/ Special New Year´s Seminar

Transthyretin (TTR) is a blood plasma protein involved in spontaneous and hereditary amyloidosis (ATTR) characterized by the presence of (amyloid) protein fibrils in numerous tissues of patients. In vivo, the molecular mechanism by which the stable, natively folded tetramer transitions to the fibrillar state remains unclear, but shear forces from fluid flow have been proposed as a contributing factor. We explored in vitro how fluid flow that is intended to mimic blood circulation can induce TTR aggregation, by a simple but efficient rapid stirring (agitation) experiment. Agitation was found to be sufficient to induce aggregation of wild-type human TTR at physiologically relevant concentrations and neutral pH. Using a combination of imaging and fluorescence we investigated aggregation kinetics and characterized aggregation intermediates. The agitation assay was supplemented by high resolution NMR experiments, and μRheo-NMR to investigate TTR aggregation under milder laminar shear stress at the molecular level. We compared human TTR to natural TTR ortholog variants from species that have evolved strongly diverging heart rates (hummingbird with fast heart rate, and African elephant with slow heart rate). Hummingbird TTR was substantially kinetically stabilized against shear-induced aggregation, which was also reflected in the kinetic stability of the native tetramer as determined by tryptophan fluorescence.