Protein aggregation and proteasome dysfunction after brain ischemia.
OBJECTIVE
Protein unfolding and aggregation are dominant early pathogenic events in neurons after brain ischemia. This study used a transient cerebral ischemia model to investigate whether overproduction of unfolded proteins after brain ischemia is a consequence of proteasome dysfunction.


METHODS
Proteasome peptidase activity and proteasome subcellular redistribution and assembly were studied by peptidase activity assay, Western blot analysis, and size-exclusion chromatography.


RESULTS
Proteasome peptidase activity, as determined with the peptide substrate succinyl-LLVY-7-amino-4-methylcoumarin, was moderately decreased, and the 26S proteasome was disassembled during the early period of reperfusion after transient brain ischemia. Furthermore, the proteasome subunits, particularly the 19S components, were deposited into the protein aggregate-containing fraction after an episode of transient cerebral ischemia.


CONCLUSIONS
These results clearly demonstrate that after an episode of brain ischemia, proteasomes are disassembled and aggregated and thus fail to function normally. Deposition of proteasomes into protein aggregates may also indicate that proteasomes attempt to degrade ubiquitin-conjugated proteins (ubiproteins) overproduced after brain ischemia. However, ubiproteins are too numerous to be degraded and trap some of the proteasomes into their aggregates after brain ischemia.
Ge
Pengfei
P
Department of Neurosurgery, First Teaching Hospital, Jilin University, Jilin, China.
Luo
Yinan
Y
Liu
Cindy L
CL
Hu
Bingren
B
D000818:Animals; D015153:Blotting, Western; D002545:Brain Ischemia / Q000378:metabolism* / Q000473:pathology*; D002845:Chromatography / Q000379:methods; D007511:Ischemia; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010447:Peptide Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions; D025801:Ubiquitin / Q000378:metabolism
D025801:Ubiquitin; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease