Cathepsin-dependent amyloid formation drives mechanical rupture of lysosomal membranes

Area of Science:

• Cell Biology
• Biochemistry
• Neuroscience

Background:

• Lysosomal membrane integrity is crucial for cellular health, and its disruption contributes to lysosomal storage disorders (LSD) and neurodegeneration.
• L-leucyl-L-leucine methyl ester (LLOMe) is a common tool to induce and study lysosomal damage, but its precise mechanism of action is not well understood.

Purpose of the Study:

• To elucidate the structural mechanism by which LLOMe causes lysosomal damage.
• To investigate the role of amyloid formation in LLOMe-induced lysosomal membrane rupture.

Main Methods:

• Cryo-electron tomography was used to visualize LLOMe-induced damage in cultured cells and primary neurons.
• In vitro reconstitution experiments were performed to confirm the observed mechanism.

Main Results:

• LLOMe forms amyloid structures within the lysosomal lumen.
• These amyloid structures directly interact with and rupture the lysosomal membrane through mechanical stress.
• The findings were validated through in vitro reconstitution.

Conclusions:

• LLOMe-induced lysosomal damage is mediated by the formation of amyloid structures that cause mechanical rupture of the lysosomal membrane.
• This study establishes a structural paradigm for lysosomal membrane disruption.
• The findings offer insights into how disease-associated protein aggregates may impair lysosomal integrity in neurodegenerative diseases and LSDs.