title: Impact of ageing on proteasome structure and function in human lymphocytes.
abstract: Key actors of the immune response, lymphocytes exhibit functional deficits with advancing age. For instance, the age-related decline in lymphocyte proliferation may be related to alteration in the degradation of crucial proteins such as cell-cycle regulators. Degradation of these proteins is mediated by the ubiquitin-26S proteasome system. The proteasome is also the major "housekeeping" proteolytic complex responsible for eliminating intracellular damaged proteins. To investigate the occurrence of proteasome structural and functional age-related alterations, 26S proteasome was purified from peripheral blood lymphocytes of 20-63-year-old donors. Changes in peptidase activity were measured and modifications in the proteasome particle structure were analysed using bi-dimensional electrophoresis. We found the age-related decline of 26S proteasome-specific activity to be associated with an increased yield of post-translational modifications of proteasome subunits, while proteasome content and subunit composition were unchanged. In particular, some catalytic and assembly subunits of the 20S proteasome were preferentially modified with age. Western blotting of proteasome subunits resolved by bi-dimensional electrophoresis showed some of these modified subunits to be glycated, conjugated with a lipid peroxidation product and/or ubiquitinated. In conclusion, it is suggested that structural alterations of proteasome subunits may contribute to the observed decline of proteasome activity with age and could play a major role in immune senescence.
authors.affiliation: Laboratoire de Biologie et Biochimie Cellulaire du Vieillissement, Université Paris 7-Denis Diderot, Case Courrier (CC) 7128, 2 Place Jussieu, 75251 Cedex 05, Paris, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Carrard
authors.forename: Marc
authors.initials: M
authors.lastname: Dieu
authors.forename: Martine
authors.initials: M
authors.lastname: Raes
authors.forename: Olivier
authors.initials: O
authors.lastname: Toussaint
authors.forename: Bertrand
authors.initials: B
authors.lastname: Friguet
mesh_terms: D000328:Adult; D000375:Aging / Q000378:metabolism*; D015153:Blotting, Western; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D004586:Electrophoresis; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology*; D008875:Middle Aged; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D018384:Oxidative Stress; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D021241:Spectrometry, Mass, Electrospray Ionization; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D014452:Ubiquitins; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease