The lysosome is the cell’s essential “scavenger”, tasked with sequestering waste and recycling nutrients. However, this digestive hub is a double-edged sword; its internal cocktail of acidic hydrolases is lethal if leaked. Lysosomal Membrane Permeabilization (LMP)—a breach in this barrier—is a hallmark of cellular aging and a primary driver of neurodegeneration and lysosomal storage disorders.
While the cell has long been known to possess repair machinery, the organizing principle behind this rapid response has remained elusive. We suggest that lysosomal injury triggers the de novo nucleation of “repair condensates.” ### The Organizing Principle of Repair This process leverages biomolecular condensation, where damage-sensing proteins undergo phase separation at the site of the breach. These condensates serve two critical functions:
Organizational Hubs: They create a concentrated environment to rapidly recruit repair machinery, such as the ESCRT complex, to the injury site.
Mechanical Stabilization: They act as a physical plug or scaffold to stabilize the compromised lipid bilayer.
Synergy with Lipid Domains
The effectiveness of these condensates is inextricably linked to lipid domain reorganization. Upon damage, the membrane’s lipid composition shifts, forming specialized domains rich in cholesterol and sphingolipids. These domains provide the necessary fluid environment and curvature to facilitate membrane budding and sealing, working in tandem with protein condensates to restore the organelle’s barrier function.
By defining these transient repair hubs, we uncover a fundamental biophysical mechanism that cells use to prevent inflammatory death and maintain proteostasis.
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