Effect of Oxidant Systems on the Ubiquitylation

ANA M. ADAMO,* LAURA A. PASQUINI, MARCOS BESIO MORENO, PATRICIA I. OTEIZA,

JOURNAL OF NEUROSCIENCE RESEARCH

Wiley-Liss, Inc

Año: 1999 vol. 55 p. 523 - 531

0360-4012

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 ATPdependent 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-molecularweight Ub protein conjugates (UbPC) and the changes in the production of 2-thiobarbituric acid–reactive substances (TBARS), in the content of proteinassociated 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.