Inhibition of the Proteasome Regulator PA28 Aggravates Oxidized Protein Overload in the Diabetic Rat Brain.

Oxidized protein overloading caused by diabetes is one accelerating pathological pathway in diabetic encephalopathy development. To determine whether the PA28-regulated function of the proteasome plays a role in diabetes-induced oxidative damaged protein degradation, brain PA28α and PA28ß interference experiments were performed in a high-fat diet (HFD) and streptozotocin (STZ)-induced rat model. The present results showed that proteasome activity was changed in the brains of diabetic rats, but the constitutive subunits were not. In vivo PA28α and PA28ß inhibition via adeno-associated virus (AAV) shRNA infection successfully decreased PA28 protein levels and further exacerbated oxidized proteins load by regulating proteasome catalytic activity. These findings suggest that the proteasome plays a role in the elimination of oxidized proteins and that PA28 is functionally involved in the regulation of proteasome activity in vivo. This study suggests that abnormal protein turbulence occurring in the diabetic brain could be explained by the proteasome-mediated degradation pathway. Changes in proteasome activity regulator PA28 could be a reason to induce oxidative aggregation in diabetic brain. Proteasome regulator PA28 inhibition in vivo by AAV vector injection could aggravate oxidized proteins abundance in brain of HFD-STZ diabetic rat model.

Genomic structural characterization and transcriptional expression analysis of proteasome activator PA28α and PA28ß subunits from Oplegnathus fasciatus.

Proteasomes are multicatalytic subunit complexes involved in the degradation of cytosolic proteins and antigen presentation. In this study, we have characterized the alpha and beta subunits of proteasome activator complex from rock bream at the molecular level. RbPA28α and RbPA28ß possessed the characteristic features of the subunits identified from mammals and teleosts. The RbPA28α and RbPA28ß proteasome subunits contained a proline-rich motif (Region A), subunit-specific insert in the region corresponding to the KEKE motif of the known PA28α (Region B), conserved activation loop (Region C), a potential protein kinase C recognition site (Region D) and a highly homologous C-terminal region (Region E) among all three PA28 subunits. Multiple sequence alignment and pairwise alignment revealed that RbPA28α and RbPA28ß proteins shared high homology with the teleosts and mammals. RbPA28α and RbPA28ß genome possessed 11 exons interrupted by 10 introns. In silico promoter analysis of RbPA28α and RbPA28ß revealed various transcription factor-binding sites displaying their regulation under various stress conditions. Tissue distribution profiling showed a higher expression in blood and gills. Transcriptional expression analysis of RbPA28α and RbPA28ß showed up-regulation in the immune tissues following LPS and poly I:C challenges, providing further evidence for the immunological role of RbPA28α and RbPA28ß.