Chronic ethanol feeding affects proteasome-interacting proteins.
Studies on alcoholic liver injury mechanisms show a significant inhibition of the proteasome activity. To investigate this phenomenon, we isolated proteasome complexes from the liver of rats fed ethanol chronically, and from the liver of their pair-fed controls, using a non-denaturing multiple centrifugations procedure to preserve proteasome-interacting proteins (PIPs). ICAT and MS/MS spectral counting, further confirmed by Western blot, showed that the levels of several PIPs were significantly decreased in the isolated ethanol proteasome fractions. This was the case of PA28alpha/beta proteasome activator subunits, and of three proteasome-associated deubiquitinases, Rpn11, ubiquitin C-terminal hydrolase 14, and ubiquitin carboxyl-terminal hydrolase L5. Interestingly, Rpn13 C-terminal end was missing in the ethanol proteasome fraction, which probably altered the linking of ubiquitin carboxyl-terminal hydrolase L5 to the proteasome. 20S proteasome and most 19S subunits were however not changed but Ecm29, a protein known to stabilize the interactions between the 20S and its activators, was decreased in the isolated ethanol proteasome fractions. It is proposed that ethanol metabolism causes proteasome inhibition by several mechanisms, including by altering PIPs and proteasome regulatory complexes binding to the proteasome.
Bousquet-Dubouch
Marie-Pierre
MP
CNRS, Institut de Pharmacologie et de Biologie Structurale, Toulouse, France. marie-pierre.bousquet@ipbs.fr
Nguen
Sheila
S
Bouyssié
David
D
Burlet-Schiltz
Odile
O
French
Samuel W
SW
Monsarrat
Bernard
B
Bardag-Gorce
Fawzia
F
D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D000431:Ethanol / Q000008:administration & dosage*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D053719:Tandem Mass Spectrometry
D008562:Membrane Glycoproteins; D000431:Ethanol; D019392:Cytochrome P-450 CYP2E1; D046988:Proteasome Endopeptidase Complex