Truncation, cross-linking and interaction of crystallins and intermediate filament proteins in the aging human lens

► Crystallins form a broad mixture of cross-linked species of ~ 40 kDa in the water-soluble fractions of human lenses of all ages. ► Low molecular weight crystallin fragments were increasingly found in the water-insoluble lens fractions with age. ► Proteolysis of beaded filament proteins occurs very early in life. ► α-Crystallin interacts with intermediate filament proteins and their breakdown products under mild heat stress.