Cathepsin C–Catalyzed Ligation Generates Intralysosomal Amyloid Fibrils from Dipeptide Esters

Amyloid fibril-associated endolysosomal dysfunction is implicated in multiple neurodegenerative diseases. We report the rapid generation of intralysosomal amyloid fibrils by simply treating cells with certain dipeptide methyl esters. Cathepsin C mediates the ligation of dipeptides into oligopeptides that, sequence-dependently, self-assemble into amyloid fibrils. Progressive fibril growth, not fibril deposition, mediates lysosomal membrane permeabilization. Cryo-electron tomography studies reveal intralysosomal fibrils and broken lysosomal membranes upon dipeptide treatment. Certain oligopeptide fibril structures are competent to cross-seed the aggregation of neurodegeneration-associated Tau(P301S) at lysosomal sites. Similarly, the degree of lysosomal membrane permeabilization and ESCRT-repair response can be tuned with dipeptide sequence variation. The presented Cathepsin C-dependent amyloid fibril formation approach lends itself toward the development of novel tools to further probe lysosomal biology and pathobiology.