Peristaltic pump-triggered amyloid formation suggests shear stresses are in vivo risk factors of amyloid nucleation

Amyloid fibrils, crystal-like fibrillar aggregates of denatured proteins, are formed linked with the breakdown of supersaturation, causing a series of amyloidosis including Alzheimer’s and Parkinson’s diseases. Although varying in vitro factors are known, in vivo factors breaking supersaturation are unclear. We found that flowing by a peristaltic pump effectively triggers amyloid formation of hen egg white lysozyme, a model amyloidogenic protein, and, moreover, amyloidosis-associated proteins (i.e. α-synuclein, amyloid β 1-40, and β2-microglobulin). The peristaltic pump-dependent amyloid formation was visualized by a fluorescence microscope with looped flow system, revealing dynamic motions under flow. Among them, amyloid fibrils of amyloid β 1-40 were stickier than others, self-associating, absorbing to loop surfaces, and surging upon flicking the loop, implying early stages of cerebral amyloid angiopathy. On the other hand, β2-microglobulin at a neutral pH showed unique two-step amyloid formation with an oligomeric trapped intermediate, which might mimic amyloid formation in patients. Peristalsis-caused strong shear stresses were considered to mechanically break supersaturation. Shearing stresses occu r in vivo at varying levels, suggesting that they break otherwise persistent supersaturation, thus triggering amyloid formation and ultimately leading to amyloidosis. (182 words <200 words)