Modulation of polyglutamine inclusion formation by the Hsp70 chaperone machine.
Components of the Hsp70 chaperone machine have been implied in protection against polyglutamine (poly-Q) pathologies. Yet, little is known about specific mechanisms and the rate-limiting components that account for this protective effect. Here, we examined the effects of an Hsp70 chaperone family member (HspA1A) and its cofactors Hsp40 (DnaJB1), Bag-1 and CHIP on poly-Q protein inclusion formation and SDS-insolubilization. Overexpression of HspA1A alone did not suppress inclusion formation, while overexpression of DnaJB1 reduced poly-Q inclusion formation and insolubilization. The reducing effect of DnaJB1 on inclusion formation was enhanced by coexpressing HspA1A, and was dependent on the interaction of DnaJB1 with Hsp70/Hsc70 chaperones. Additionally, two factors connecting Hsp70 activity with protein degradation by the ubiquitin-proteasome system Bag-1 and CHIP slightly decreased the levels of soluble poly-Q protein, but the amount of aggregated protein and fraction of cells with inclusions remained unaltered. Our data suggest that the HspA1A chaperone machine can modulate poly-Q inclusion formation depending on the ratio of its components and that DnaJB1 is the rate-limiting step.
Rujano
M A
MA
Department of Cell Biology, Section of Radiation & Stress Cell Biology, University Medical Center Groningen, University of Groningen, The Netherlands.
Kampinga
H H
HH
Salomons
F A
FA
D000818:Animals; D016923:Cell Death; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009447:Neuroblastoma / Q000473:pathology; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D012995:Solubility; D013997:Time Factors