How “extracellular chaperones” help remove abnormal proteins

When exposed to stressful conditions, several proteins tend to misfold and form aggre-gates inside or outside cells. These aggregates, if accumulated, may contribute to age-related disorders, including Alzheimer’s disease. Extracellular chaperones stabilize mis-folded proteins to prevent their aggregation and have been implicated in clearing these defective proteins outside cells, but their mechanisms are poorly understood. Now, re-searchers from Chiba University have developed an assay that can detect this process quantitatively and have uncovered that extracellular chaperones mediate the lysosomal degradation of extracellular misfolded proteins.