Effect of oxidant systems on the ubiquitylation of proteins in the central nervous system.
Ubiquitin (Ub) modification of different proteins plays an important role in many cellular processes. However, the best studied function of Ub is the labeling of proteins committed to rapid degradation, by an ATP-dependent pathway. We previously found that this pathway is operative in the central nervous system (CNS) of adult rats (Adamo et al. [1994] J. Neurosci. Res. 38:358-364). In the present study, we examined the changes in the capacity to form high-molecular-weight Ub protein conjugates (UbPC) and the changes in the production of 2-thiobarbituric acid-reactive substances (TBARS), in the content of protein-associated carbonyl groups (PAC), and in the activity of glutamine synthetase produced by in vitro peroxidation of the cell cytosolic proteins and of the mitochondrial fraction isolated from rat brain. Under these experimental conditions, there was an increase in PAC and TBARS in the cytosol, indicating that damage to certain cellular components had occurred. Simultaneously there was a marked increase in UbPC in comparison with the nonoxidized controls. These conjugates showed an active turnover and accumulated when Ub-mediated proteolysis was inhibited. In vitro peroxidation of the mitochondrial fractions resulted in an increase in the production of PAC and in an enhancement in the formation of UbPC. These results demonstrate that the oxidized proteins can be recognized by the ubiquitylating system and that in the CNS the Ub-dependent proteolytic pathway is one of the possible mechanisms involved in the removal of cytosolic and mitochondrial fraction damaged proteins.
Adamo
A M
AM
Institute of Biological and Physical Biochemistry (IQUIFIB), UBA-CONICET, and Department of Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina.
Pasquini
L A
LA
Moreno
M B
MB
Oteiza
P I
PI
Soto
E F
EF
Pasquini
J M
JM
D000818:Animals; D001921:Brain / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014452:Ubiquitins / Q000378:metabolism*
D009097:Multienzyme Complexes; D011506:Proteins; D014452:Ubiquitins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex