Network Accessibility Limits Enzymatic Degradation of Interfacial Amyloid Networks

Amyloid plaques, formed at biological interfaces by aberrant accumulation of amyloid fibrils, are a pathological hallmark of several neurodegenerative diseases. While clearance of interfacial amyloid plaques is a promising clinical strategy, an analytical platform for elucidating the degradation mechanism of interfacial amyloid networks has not been established. In this study, we establish a framework to analyze the degradation kinetics of interfacial amyloid networks by proteinase K using a multichannel wireless quartz crystal microbalance. The results show that enzymatic degradation of the interfacial amyloid network composed of α-synuclein fibrils proceeds via a two-step mechanism. The two-step degradation comprises exposure of fibrils buried within the network to the solution, followed by proteolytic removal of the exposed fibrils into solution. Further quantitative analysis reveals that the initial exposure process is the rate-limiting step in interfacial degradation and that the removal rate is jointly governed by the proteolytic activity of the degrading agents and the morphology of the interfacial networks, which are not kinetically interchangeable. These findings suggest that unraveling the amyloid network, rather than enhancing proteolytic activity against dispersed fibrils, is more important for effective clearance of interfacial amyloid networks.