title: Age-dependent protein modifications and declining proteasome activity in the human lens.
abstract: The proteasome is known to be the main enzymatic complex responsible for the intracellular degradation of altered proteins, and the age-related accumulation of modified lens proteins is associated to the formation of cataracts. The aim of this study was to determine whether the human lens proteasome becomes functionally impaired with age. The soluble and insoluble protein fractions of human lenses corresponding to various age-groups were characterized in terms of their levels of glyco-oxidative damage and found to show increasing anti-carboxymethyl-lysine immunoreactivity with age. Concomitantly, decreasing proteasome contents and peptidase activities were observed in the water-soluble fraction. The fact that peptidylglutamyl-peptide hydrolase activity is most severely affected with age suggests that specific changes are undergone by the proteasome itself. In particular, increasing levels of carboxymethylation were observed with age in the proteasome. It was concluded that the lower levels of soluble active enzymatic complex present in elderly lenses and the post-translational modifications affecting the proteasome may at least partly explain the decrease in proteasome activity and the concomitant accumulation of carboxymethylated and ubiquitinated proteins which occur with age.
authors.affiliation: Laboratorio de Química Biológica, Facultad de Química, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Comuna Macul, Santiago, Chile.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Viteri
authors.forename: Géraldine
authors.initials: G
authors.lastname: Carrard
authors.forename: Inès
authors.initials: I
authors.lastname: Birlouez-Aragón
authors.forename: Eduardo
authors.initials: E
authors.lastname: Silva
authors.forename: Bertrand
authors.initials: B
authors.lastname: Friguet
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000378:metabolism*; D002102:Cadaver; D002675:Child, Preschool; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D004795:Enzyme Stability; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D007231:Infant, Newborn; D007908:Lens, Crystalline / Q000378:metabolism*; D008875:Middle Aged; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D046988:Proteasome Endopeptidase Complex
chemical_list: D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex