Induction and selective accumulation of mutant ubiquitin in CA1 pyramidal neurons after transient global ischemia.
Accumulation of mutant ubiquitin-B (UBB(+1)) in neurons is considered the hallmark of proteasomal dysfunction in neurodegenerative disorders, however no such evidence in ischemic brain has been reported. We investigated the contribution of UBB(+1) in delayed neuronal death after transient global ischemia. Transient global ischemia was achieved by occlusion of bilateral common carotid arteries for 5 min and reperfusion in male Mongolian gerbils (n=6 per each time point). In the CA1 region, UBB(+1) immunoreactivity appeared in the cytoplasm of pyramidal cells at 30 min post-ischemia, and the density of these neurons increased at day 2 (P<0.001) and further increased at day 4 post-ischemia. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL)-positive (apoptotic) cells appeared selectively in the CA1 region at day 3 and their density increased further at day 4 post-ischemia (P<0.001). In contrast, UBB(+1) immunoreactivity was only transiently detected from 30 min to 1 day post-ischemia in CA3, dentate gyrus, and frontal cortex, but disappeared at day 2 post-ischemia. No TUNEL-positive cells were observed in these three regions. UBB(+1) mRNA was detected by reverse transcription-polymerase chain reaction in every region of the hippocampus and frontal cortex of ischemic gerbils and even in the non-ischemic control animals, and its expression level was independent of brain region and time after ischemia. Our results indicate induction and selective accumulation of UBB(+1) protein in dying neurons of the CA1 region and suggest that UBB(+1) expression may be induced by proteasomal dysfunction after transient global ischemia.
Yamashiro
K
K
Department of Neurology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Liu
R
R
Maeda
M
M
Hattori
N
N
Urabe
T
T
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism* / Q000503:physiopathology; D016923:Cell Death / Q000502:physiology; D005625:Frontal Lobe / Q000166:cytology / Q000378:metabolism; D005849:Gerbillinae; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D017966:Pyramidal Cells / Q000378:metabolism*; D017384:Sequence Deletion / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes