title: Impairment of proteasome function upon UVA- and UVB-irradiation of human keratinocytes.
abstract: The major environmental influence for epidermal cells is sun exposure and the harmful effect of UV radiation on skin is related to the generation of reactive oxygen species that are altering cellular components including proteins. It is now well established that the proteasome is responsible for the degradation of oxidized proteins. Therefore, the effects of UV-irradiation on proteasome have been investigated in human keratinocyte cultures. Human keratinocytes were irradiated with 10 J/cm(2) of UVA and 0.05 J/cm(2) of UVB and proteasome peptidase activities were measured in cell lysates using fluorogenic peptides. All three peptidase activities were decreased as early as 1 h and up to 24 h after irradiation of the cells. Increased levels of oxidized and ubiquitinated proteins as well as proteins modified by the lipid peroxidation product 4-hydroxy-2-nonenal were also observed in irradiated cells. However, immunopurified 20S proteasome exhibited no difference in both peptidase specific activities and 2D gel pattern of subunits in irradiated cells, ruling out the possibility that the 20S proteasome could be a target for the UV-induced damage. Finally, extracts from irradiated keratinocytes were able to inhibit degradation by the proteasome, demonstrating the presence of endogeneous inhibitors, including 4-hydroxy-2-nonenal modified proteins, generated upon UV-irradiation.
authors.affiliation: Laboratoire de Biologie et Biochimie Cellulaire du Vieillissement, Université Paris, 7-Denis Diderot, Paris, France.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Bulteau
authors.forename: Marielle
authors.initials: M
authors.lastname: Moreau
authors.forename: Carine
authors.initials: C
authors.lastname: Nizard
authors.forename: Bertrand
authors.initials: B
authors.lastname: Friguet
mesh_terms: D000447:Aldehydes / Q000494:pharmacology; D015153:Blotting, Western; D001940:Breast / Q000201:enzymology / Q000528:radiation effects; D002364:Caseins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D004817:Epidermis / Q000528:radiation effects; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000201:enzymology / Q000528:radiation effects*; D008875:Middle Aged; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014452:Ubiquitins / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000447:Aldehydes; D002364:Caseins; D017931:DNA Primers; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D014452:Ubiquitins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C027576:4-hydroxy-2-nonenal