Many neurodegenerative diseases including Alzheimer, Parkinson, and polyglutamine (polyQ) diseases are thought to be caused by protein misfolding. The polyQ diseases, including Huntington disease and spinocerebellar ataxias (SCAs), are caused by abnormal expansions of the polyQ stretch in disease-causing proteins, which trigger misfolding of these proteins, resulting in their deposition as inclusion bodies in affected neurons. Although genetic expression of molecular chaperones has been shown to suppress polyQ protein misfolding and neurodegeneration, toward developing a therapy, it is ideal to induce endogenous molecular chaperones by chemical administration. In this study, we assessed the therapeutic effects of heat shock transcription factor 1 (HSF1)-activating compounds, which induce multiple molecular chaperones, on polyQ-induced neurodegeneration in vivo. We found that oral administration of 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) markedly suppresses compound eye degeneration and inclusion body formation in a Drosophila model of SCA. 17-AAG also dramatically rescued the lethality of the SCA model (74.1% rescue) and suppressed neurodegeneration in a Huntington disease model (46.3% rescue), indicating that 17-AAG is widely effective against various polyQ diseases. 17-AAG induced Hsp70, Hsp40, and Hsp90 expression in a dose-dependent manner, and the expression levels correlated with its therapeutic effects. Furthermore, knockdown of HSF1 abolished the induction of molecular chaperones and the therapeutic effect of 17-AAG, indicating that its therapeutic effects depend on HSF1 activation. Our study indicates that induction of multiple molecular chaperones by 17-AAG treatment is a promising therapeutic approach for a wide range of polyQ diseases and possibly other neurodegenerative diseases.

Abnormal aggregation of misfolded proteins and their deposition as inclusion bodies in the brain have been implicated as a common molecular pathogenesis of neurodegenerative diseases including Alzheimer, Parkinson, and the polyglutamine (poly(Q)) diseases, which are collectively called the conformational diseases. The poly(Q) diseases, including Huntington disease and various types of spinocerebellar ataxia, are caused by abnormal expansions of the poly(Q) stretch within diseasecausing proteins, which triggers the disease-causing proteins to aggregate into insoluble ␤-sheet-rich amyloid fibrils. Although oligomeric structures formed in vitro are believed to be more toxic than mature amyloid fibrils in these diseases, the existence of oligomers in vivo has remained controversial. To explore oligomer formation in cells, we employed fluorescence correlation spectroscopy (FCS), which is a highly sensitive technique for investigating the dynamics of fluorescent molecules in solution. Here we demonstrate direct evidence for oligomer formation of poly(Q)-green fluorescent protein (GFP) fusion proteins expressed in cultured cells, by showing a time-dependent increase in their diffusion time and particle size by FCS. We show that the poly(Q)-binding peptide QBP1 inhibits poly(Q)-GFP oligomer formation, whereas Congo red only inhibits the growth of oligomers, but not the initial formation of the poly(Q)-GFP oligomers, suggesting that FCS is capable of identifying poly(Q) oligomer inhibitors. We therefore conclude that FCS is a useful technique to monitor the oligomerization of disease-causing proteins in cells as well as its inhibition in the conformational diseases.Abnormal aggregation and deposition of misfolded proteins in the brain have been implicated as a common molecular pathogenesis of neurodegenerative diseases including Alzheimer disease, Parkinson disease, and the polyglutamine (poly(Q)) 2 diseases, which are collectively called the conformational diseases (1-3). The poly(Q) diseases are a group of at least nine inherited neurodegenerative diseases including Huntington disease and various types of spinocerebellar ataxia, which are caused by abnormal expansions of the poly(Q) stretch to above 40 glutamines within each unrelated diseasecausing protein (4, 5). In the pathogenesis of the poly(Q) diseases, expansions of the poly(Q) stretch in disease-causing proteins are believed to cause alterations in the protein conformation, resulting in assembly of the proteins into insoluble ␤-sheet-rich amyloid-like fibrillar aggregates, and eventually their deposition as inclusion bodies inside affected neurons. However, Finkbeiner and colleagues (6) demonstrated that neuronal cells with poly(Q) protein inclusions have a decreased risk of death, suggesting that the diffuse poly(Q) protein rather than inclusion bodies causes cytotoxicity. Inclusion bodies, which are large intracellular deposits of aggregated proteins, are believed to be formed as a cytoprotective response against the overproduction of misfolded/aggregated pro...

Although ribosomal proteins (RPs) are essential cellular constituents in all living organisms, mechanisms underlying regulation of their gene expression in mammals remain unclear. We have established that 22 out of 79 human RP genes contain sequences similar to the human DREF (DNA replication-related elementbinding factor; hDREF) binding sequence (hDRE) within 200-bp regions upstream of their transcriptional start sites. Electrophoretic gel mobility shift assays and chromatin immunoprecipitation analysis indicated that hDREF binds to hDRE-like sequences in the RP genes both in vitro and in vivo. In addition, transient luciferase assays revealed that hDRE-like sequences act as positive elements for RP gene transcription and cotransfection of an hDREF-expressing plasmid was found to stimulate RP gene promoter activity. Like that of hDREF, expression of RP genes is increased during the late G 1 to S phases, and depletion of hDREF using short hairpin RNA-mediated knockdown decreased RP gene expression and cell proliferation in normal human fibroblasts. Knockdown of the RPS6 gene also resulted in impairment of cell proliferation. These data suggest that hDREF is an important transcription factor for cell proliferation which plays roles in cell cycle-dependent regulation of a number of RP genes.Promoters of Drosophila melanogaster genes related to DNA replication, such as those for the 180-kDa catalytic subunit of DNA polymerase ␣ and proliferating cell nuclear antigen (PCNA), contain a common 8-bp palindromic sequence (5Ј-T ATCGATA-3Ј), named the DNA replication-related element (DRE) (12). These DREs are required for promoter activities both in cultured cells and in flies in vivo (41). We have purified the DRE-binding factor (DREF) from cultured Drosophila cells, consisting of an 86-kDa polypeptide homodimer specifically binding to DRE, and isolated a cDNA (12, 13). The importance of Drosophila DREF in development has been demonstrated from studies using transgenic flies (11,14,44). For example, ectopic expression of Drosophila DREF in eye imaginal disc cells behind the morphogenetic furrow, which are normally postmitotic, induced ectopic DNA synthesis and apoptosis and abolished photoreceptor specifications (11). More recently, we and Hyun et al. have succeeded in knocking down Drosophila DREF expression in various tissues (16,45). Decreased levels of DREF in developing wing and eye imaginal discs were associated with reduction in wing size with smaller cells and drastically aberrant small and rough eyes, respectively. These lines of evidence indicate that the Drosophila DRE/DREF system performs important roles in regulation of cell growth as well as cell proliferation during development.How many and what kind of genes other than those described above are under control of the Drosophila DRE/DREF system? Immunostaining of polytene chromosomes of salivary glands revealed that Drosophila DREF binds to hundreds of loci (8, 10), and recent computational analysis of core promoters in the Drosophila genome showed DRE to be...

Background: Oligomers of pathogenic proteins are implicated in the pathomechanisms of neurodegenerative diseases. Results: Depletion of p62 delays the degradation of polyglutamine protein oligomers via autophagy and exacerbates neurodegeneration in polyglutamine disease model flies. Conclusion: p62 plays a protective role via autophagic degradation of polyglutamine protein oligomers. Significance: p62 should be a therapeutic target for the polyglutamine diseases.