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A screen for enhancers of clearance identifies huntingtin as an heat shock protein 90 (Hsp90) client protein

Baldo, Barbara, Weiss, Andreas, Parker, Christian, Bibel, Miriam, Paganetti, Paolo and Kaupmann, Klemens (2011) A screen for enhancers of clearance identifies huntingtin as an heat shock protein 90 (Hsp90) client protein. Journal of Biological Chemistry, http:/. ISSN 0021-9258


Mechanisms to reduce the cellular levels of mutant huntingtin (mHtt) provide promising strategies for treating Huntington’s disease (HD). To identify compounds enhancing the degradation of mHtt we performed a high throughput screen, using a hippocampal HN10 cell line expressing a 573 amino acid mHtt fragment. Several hit structures were identified as heat shock protein 90 (Hsp90) inhibitors. Cell treatment with these compounds reduced levels of mHtt as measured by time-resolved Förster resonance energy transfer assays and western blots, without overt toxic effects. To characterize the mechanism of mHtt degradation, we used the potent and selective Hsp90 inhibitor NVP-AUY922. In HdhQ150 embryonic stem (ES) cells and in ES derived neurons, NVP-AUY922 treatment substantially reduced soluble full-length mHtt levels. In HN10 cells, Hsp90 inhibition by NVP-AUY922 enhanced mHtt clearance in the absence of any detectable heat shock protein 70 (Hsp70) induction. Furthermore, inhibition of protein synthesis with cycloheximide or overexpression of dominant-negative heat shock factor 1 (Hsf1) in HdhQ150 ES cells attenuated Hsp70 induction, but did not affect NVP-AUY922 mediated mHtt clearance. Together, these data provided evidence that direct inhibition of Hsp90 chaperone function was crucial for mHtt degradation, rather than heat shock response induction and Hsp70 upregulation. Co-immunoprecipitation experiments revealed a physical interaction of mutant and wild-type Htt with the Hsp90 chaperone. Hsp90 inhibition disrupted the interaction and induced clearance of Htt through the ubiquitin proteasome system. Our data suggest that Htt is an Hsp90 client protein and that Hsp90 inhibition may provide a means to reduce mHtt in HD.

Item Type: Article
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Additional Information: Previous Novartis/ NS publication on this topic: Investigating the role of protein modification in Huntington’s disease: the importance of Htt and Hsp90 interaction in protein clearance and stability Full Text Status: Public Presentation Type: Abstract Keywords: mutant huntingtin, HN10 cells, Hsp90 inhibitors Date: April 2010 Event Title: HD2010: "The Milton Wexler Celebration of Life" Event Location: Boston, USA Event Dates: 4-7 August 2010
Keywords: Huntington's disease, heat shock protein 90, neurodegeneration, NVP-AUY922
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Date Deposited: 13 Oct 2015 13:15
Last Modified: 13 Oct 2015 13:15


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