β2-microglobulin amyloid fibrils are nanoparticles that disrupt lysosomal membrane protein trafficking and inhibit protein degradation by lysosomes.
Fragmentation of amyloid fibrils produces fibrils that are reduced in length but have an otherwise unchanged molecular architecture. The resultant nanoscale fibril particles inhibit the cellular reduction of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), a substrate commonly used to measure cell viability, to a greater extent than unfragmented fibrils. Here we show that the internalization of β2-microglobulin (β2m) amyloid fibrils is dependent on fibril length, with fragmented fibrils being more efficiently internalized by cells. Correspondingly, inhibiting the internalization of fragmented β2m fibrils rescued cellular MTT reduction. Incubation of cells with fragmented β2m fibrils did not, however, cause cell death. Instead, fragmented β2m fibrils accumulate in lysosomes, alter the trafficking of lysosomal membrane proteins, and inhibit the degradation of a model protein substrate by lysosomes. These findings suggest that nanoscale fibrils formed early during amyloid assembly reactions or by the fragmentation of longer fibrils could play a role in amyloid disease by disrupting protein degradation by lysosomes and trafficking in the endolysosomal pathway.
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Toral
T
Jakhria
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Andrew L
AL
Hellewell
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Morwenna Y
MY
Porter
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Matthew P
MP
Jackson
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Kevin W
KW
Tipping
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Wei-Feng
WF
Xue
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
Sheena E
SE
Radford
From the School of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom e.w.hewitt@leeds.ac.uk.
Eric W
EW
Hewitt
D000682:Amyloid / Q000502:physiology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D053758:Nanoparticles / Q000378:metabolism; D010084:Oxidation-Reduction; D010539:Permeability; D021381:Protein Transport; D059748:Proteolysis; D001613:beta 2-Microglobulin / Q000502:physiology*
D000682:Amyloid; D008565:Membrane Proteins; D001613:beta 2-Microglobulin
Amyloid; Fibril; Lysosome; Membrane Trafficking; Protein Degradation