The induction levels of heat shock protein 70 differentiate the vulnerabilities to mutant huntingtin among neuronal subtypes.
The reason why vulnerabilities to mutant polyglutamine (polyQ) proteins are different among neuronal subtypes is mostly unknown. In this study, we compared the gene expression profiles of three types of primary neurons expressing huntingtin (htt) or ataxin-1. We found that heat shock protein 70 (hsp70), a well known chaperone molecule protecting neurons in the polyQ pathology, was dramatically upregulated only by mutant htt and selectively in the granule cells of the cerebellum. Granule cells, which are insensitive to degeneration in the human Huntington's disease (HD) pathology, lost their resistance by suppressing hsp70 with siRNA, whereas cortical neurons, affected in human HD, gained resistance by overexpressing hsp70. This indicates that induction levels of hsp70 are a critical factor for determining vulnerabilities to mutant htt among neuronal subtypes. CAT (chloramphenicol acetyltransferase) assays showed that CBF (CCAAT box binding factor, CCAAT/enhancer binding protein zeta) activated, but p53 repressed transcription of the hsp70 gene in granule cells. Basal and mutant htt-induced expression levels of p53 were remarkably lower in granule cells than in cortical neurons, suggesting that different magnitudes of p53 are linked to distinct induction levels of hsp70. Surprisingly, however, heat shock factor 1 was not activated in granule cells by mutant htt. Collectively, different levels of hsp70 among neuronal subtypes might be involved in selective neuronal death in the HD pathology.
Tagawa
Kazuhiko
K
Department of Neuropathology, Medical Research Institute and 21st Century Center of Excellence Program for Brain Integration and Its Disorders, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
Marubuchi
Shigeki
S
Qi
Mei-Ling
ML
Enokido
Yasushi
Y
Tamura
Takuya
T
Inagaki
Reina
R
Murata
Miho
M
Kanazawa
Ichiro
I
Wanker
Erich E
EE
Okazawa
Hitoshi
H
D000328:Adult; D000368:Aged; D000818:Animals; D002415:Cats; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism / Q000473:pathology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008875:Middle Aged; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000502:physiology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D018840:HSP70 Heat-Shock Proteins; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins