Macromolecular crowding and supersaturation protect hemodialysis patients from the onset of dialysis-related amyloidosis

Abstract

Dialysis-related amyloidosis (DRA), a serious complication among long-term hemodialysis patients, is caused by amyloid fibrils of β2-microglobulin (β2m). Although high serum β2m levels and a long dialysis vintage are the primary and secondary risk factors for the onset of DRA, respectively, patients with these do not always develop DRA, indicating that there are additional risk factors. To clarify these unknown factors, we investigate the effects of human sera on β2m amyloid fibril formation, revealing that sera markedly inhibit amyloid fibril formation. Results from over 100 sera indicate that, although the inhibitory effects of sera deteriorate in long-term dialysis patients, they are ameliorated by maintenance dialysis treatments in the short term. Serum albumin prevents amyloid fibril formation based on macromolecular crowding effects, and decreased serum albumin concentration in dialysis patients is a tertiary risk factor for the onset of DRA. We construct a theoretical model assuming cumulative effects of the three risk factors, suggesting the importance of monitoring temporary and accumulated risks to prevent the development of amyloidosis, which occurs based on supersaturation-limited amyloid fibril formation in a crowded milieu.

Detection of Fibril Nucleation in Micrometer-Sized Protein Condensates and Suppression of Sup35NM Fibril Nucleation by Liquid–Liquid Phase Separation

“…It should be noted that agarose did not affect the motility of the Sup35NM molecule in the droplets, as shown in Figure 2C. In addition, stabilizing certain protein structures in the crowding environment 47 of the droplets may reduce amyloid nucleation. The detailed molecular mechanism must be investigated using other analytical methods, such as fluorescence protein−protein interaction analysis.…”

Mechanisms of polyphosphate-induced amyloid fibril formation triggered by breakdown of supersaturation

“…So far, we have developed a Handai amyloid burst inducer (HANABI) by combining a water bath-type ultrasonicator and microplate reader, which has made it possible to automate amyloid fibril formation of amyloidogenic proteins [68]. Moreover, controlling the oscillation amplitude and frequency of each transducer, we have developed an optimized sonoreactor, which has improved reproducibility and the control of amyloid fibril formation (Figure 7) [69][70][71]. Although the protein-misfolding cyclic amplification (PMCA) makes it possible to detect pathological amyloid fibrils formed in vivo with high sensitivity using ultrasonication [72,73], the HANABI system, in addition, effectively stimulates the solution to disrupt the supersaturation state and promote spontaneous amyloid fibril formation.…”

Kinetic quantitative analysis reveals the suppression of Sup35NM amyloid fibril nucleation by liquid-liquid phase separation.

“…For instance, the high viscosity of the droplets (40) reduces the nucleation rate, as is thought to occur in semi-crystalline polymers (41). The stabilization of certain protein structures in the crowding environment (42) of the droplets may reduce amyloid nucleation. The detailed molecular mechanism must be investigated using other analytical methods, such as fluorescence proteinprotein interaction analysis.…”