Heat shock protein 70 alters the endosome-lysosomal localization of huntingtin.
Huntington's disease is caused by CAG trinucleotide expansions in the gene encoding huntingtin. N- terminal fragments of huntingtin with polyglutamine produce aggregates in the endosome-lysosomal system, where proteolytic fragments of huntingtin is generated. Heat shock protein 70 (HSP70) prevents the formation of protein aggregates, but the effect of HSP70 on the huntingtin in the endosome-lysosomal system is unknown. This study was to determine whether HSP70 alters the distribution of huntingtin in endosome-lysosomal system. HSP70 expressing stable cells (NIH/3T3 or cerebral hybrid cell line A1) were generated, and mutant [(CAG)(100)] huntingtin was transiently overexpressed. Analysis of subcellular distribution by immunocytochemistry or proteolysis cleavage by Western blotting was performed. 18 CAG repeat wild type [WT; (CAG)(18)] huntingtin was used as a control. Cells with huntingtin showed patterns of endosome-lysosomal accumulation, from a "dispersed vacuole (DV)" type into a coalescent "perinuclear vacuole (PV)" type over time. In WT huntingtin, HSP70 increased the cells with the PV types that enhanced the proteolytic cleavage of huntingtin. However, HSP70 reduced cells of the DV and PV types expressing mutant huntingtin, that result in less proteolysis than that of control. In addition, intranuclear inclusions were formed only in mutant cells, which was not affected by HSP70. These results suggest that HSP70 alters the distribution of huntingtin in the endosome- lysosomal system, and that this contributes to huntingtin proteolysis.
Kang
Bong Sun
BS
Department of Neurology, Clinical Research Institute, Seoul National University Hospital, Seoul 110-744, Korea.
Ahn
Jin-Young
JY
Kim
Min Ky
MK
Kim
Hyun-Jeong
HJ
Kang
Lami
L
Lim
Hun-Chang
HC
Park
Kyung-Sook
KS
Lee
Jae-Seon
JS
Seo
Jeong-Sun
JS
Cha
Choong Ik
CI
Kim
Seung U
SU
Park
Yoon Jeong
YJ
Kim
Manho
M
D000818:Animals; D002470:Cell Survival; D003593:Cytoplasm / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism
D018840:HSP70 Heat-Shock Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010447:Peptide Hydrolases