Proteolysis of Oxidized Proteins after Oxygen–Glucose Deprivation in Rat Cortical Neurons is Mediated by the Proteasome

Abstract

Oxidative injury contributes to cellular damage during and after cerebral ischemia. However, the downstream catabolic pathways of damaged cellular components in neurons are largely unknown. In the current study, the authors examined the formation of oxidized proteins and their active degradation by the proteasome. In near-pure rat primary cortical neurons, it was found that protein-bound carbonyls as markers for oxidized proteins are increased after oxygen-glucose deprivation (OGD). During and after OGD, degradation of proteins metabolically radiolabeled before OGD increases two-to threefold compared with the normal protein turnover. Proteolysis after reoxygenation was attenuated by the presence of dimethylthiourea, a radical scavenger, and was blocked by lactacystin, a specific proteasome inhibitor. Lactacystin also increased the amount of protein carbonyls formed. In contrast, the activity of the proteasome complex itself after OGD was not different from sham-washed controls. The authors suggest that oxygen-glucose deprivation increases free radicals, which, in turn, oxidize proteins that are recognized and actively degraded by the proteasome complex. This protease itself is relatively resistant against oxidative injury. The authors conclude that the proteasome may be an active part of the cellular defense system against oxidative stress after cerebral ischemia.

Role of the ubiquitin–proteasome system in brain ischemia: Friend or foe?

“…Inhibition of the proteasome was shown to prevent proteolysis of oxidized proteins after OGD, suggesting a role for the UPS in the clearance of oxidized proteins in neuronal cells. Moreover, proteasomal activity was found to be similar immediately after OGD and in sham-washed cultured cortical neurons (Weih et al, 2001), in agreement with the relative resistance of the proteasome against oxidative stress (Reinheckel et al, 1998). However, these results contrast with the protein aggregation and reduced cytosolic and nuclear free ubiquitin distribution reported in the organotypic hippocampal slice culture model of OGD (Ouyang et al, 2005).…”

“…The upregulation in oxidized proteins is coupled to an increase in protein degradation, both during and after OGD (Weih et al, 2001). Inhibition of the proteasome was shown to prevent proteolysis of oxidized proteins after OGD, suggesting a role for the UPS in the clearance of oxidized proteins in neuronal cells.…”

Circulating proteasome activity following mild head injury in children

“…Weih et al demonstrated that proteasome activation is needed for the proteolysis of oxidized proteins in cortical neurons under glucose and oxygen deprivation [34]. Another study showed that enhancement of proteasome activity potentially reduces neuronal vulnerability to oxidative injury [35].…”

Chronic traumatic encephalopathy-integration of canonical traumatic brain injury secondary injury mechanisms with tau pathology

“…Interestingly, It has been hypothesized that one reason oligomeric tau is able to accumulate in tauopathies is due to the fact that both oligomeric tau and cleaved forms of tau, which have an increased propensity for aggregation compared to full-length tau, are preferentially degraded via autophagy (Chesser et al , 2013), a pathway reported to be defective in tauopathies (Piras et al , 2016) and TBI (Sarkar et al , 2014). Although proteasome dysfunction, the mechanism which preferentially degrades monomeric tau, has also been reported to occur following TBI due to mechanisms such as oxidative stress (Bader and Grune, 2006; Weih et al , 2001; Yao et al , 2008), monomeric full-length tau has a decreased propensity to aggregate compared to cleaved tau (Chesser et al , 2013) and is less toxic than oligomeric tau (Spires-Jones et al , 2011). …”

“…In addition to cytoskeletal degradation, protein accumulation following TBI can also occur due to proteasomal dysfunction (Yao et al, 2008). In particular, the proteasome is responsible for the degradation of oxidatively damaged proteins, however, it is also subject to oxidative stress-induced impairment itself (Bader and Grune, 2006; Weih et al, 2001; Yao et al, 2008). In addition to protein accumulation following injury, impairment of axonal transport also leads to somatodendritic accumulation of organelles, such as the mitochondria (Kilinc et al, 2008), although, impairment of mitochondrial dynamics following TBI is complex and includes additional processes such as alterations in fission and fusion (Fischer et al, 2016).…”