Abstract
The wild type huntingtin protein (Htt), supports the production of brain-derived neurotrophic factor (BDNF), a survival factor for striatal neurons, through cytoplasmic sequestering of RE-1silencing transcription factor (REST). In Huntington´s Disease an inherited degenerative disease, caused by a CAG expansion in the 5´coding region of the gene, the mutant huntingtin protein (mHtt), causes that REST enters pathologically into the nucleus of cells, resulting in the repression of neuronal genes including BDNF, resulting in the progressive neuronal death. It has been reported that Htt associates with Hsp90 and this interaction is involved in regulation of huntingtin aggregation. Discovering mechanisms to reduce the cellular levels of mutant huntingtin and REST provide promising strategies for treating Huntington disease. Here, we use the yeast two-hybrid system to show that N-terminus or REST interacts with the heat shock protein 90 (Hsp90) and identifies REST as an Hsp90 Client Protein. To assess the effects of Hsp90 we used antisense oligonucleotide, and evaluated the levels mHtt and REST levels. Our results show that direct knockdown of endogenous Hsp90 significantly reduces the levels of REST and mutant Huntingtin, decreased the percentage of cells with mHtt in nucleus and rescued cells from mHtt-induced cellular cytotoxicity. Additionally Hsp90–specific inhibitors geldanamicyn and PUH71 dramatically reduced mHtt and REST levels, thereby providing neuroprotective activity. Our data show that Hsp90 is necessary to maintain the levels of REST and mHtt, which suggests that the interactions between Hsp90-REST and Hsp90-Huntingtin could be potential therapeutic targets in Huntington's disease.
Highlights
Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by the mutant huntingtin protein
We examined whether heat shock protein 90 (Hsp90) antisense oligos (ASO) has an effect on the percentage of cells containing mutant huntingtin protein (mHtt) in nucleus, we found at 24 h and 48 h that the percentage of cells co-transfected with mHtt and Hsp90 ASO was of 21.1% and 29.66%, compared to without Hsp90 ASO that was of 77.66% and 84.33%
RE-1silencing transcription factor (REST) expression regulation and how it modulates the expression of its target genes should be understood as a dynamic process that depends on time, site, REST levels, and the coincidence of cofactors, corepressor expression, degradation enzymes, and stability
Summary
Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by the mutant huntingtin protein (mHtt). The molecular basis of the disease lies in the expansion of CAG repeats in the first exon of the huntingtin gene (Htt), the mutant protein contains an abnormally long polyglutamine stretch at the N terminus [1]. Htt sustains the production of brain-derived neurotrophic factor (BDNF), a survival factor for striatal neurons, through cytoplasmic sequestering of repressor element-1 transcription factor/neuron-restrictive silencer factor (REST/NRSF) [5, 6], a major silencing transcription factor that regulates the expression of numerous neuronal genes, through its binding to a sequence of 21 base pairs, called repressor element 1 (RE1) [7]. Stress-induced epigenetic chromatin remodeling is a major regulator of neuronal gene expression and influences phenotypic responses, i.e. resilience or vulnerability [11,12,13]
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