How much cell death directly contributes to the manifestations of polyglutamine diseases is unclear

How much cell death directly contributes to the manifestations of polyglutamine diseases is unclear. Although there is usually evidence of m-Tyramine hydrobromide apoptosis in cell culture models of polyglutamine toxicity (39), cell death is not seen in some animal models (40), which implies that neuronal dysfunction may be more important than cell death in the disease process. they likely share the same mechanism, in which the expanded polyglutamine tract confers a novel, toxic property on the disease protein. Characterization of that novel property remains a central goal of polyglutamine disease research. One hypothesis is usually that expanded polyglutamine causes altered gene transcription. Nuclear accumulation of mutant protein may disrupt the transcriptional machinery by recruiting other polyglutamine-containing proteins, many of which are transcription factors (10C12). Key components of the transcription apparatus are sequestered in polyglutamine-containing inclusions (13C18). Two polyglutamine diseases are caused by expansions in known transcription factors, the androgen receptor (AR) and TATA-binding protein (8, 9). Other nuclear factors with altered distribution in the presence of mutant polyglutamine include the steroid receptor coactivator-1 (SRC-1), cAMP response element binding protein (CREB)-binding protein (CBP), nuclear corepressor, p53, and TAFII130 (13C18). Overexpression of CBP and TAFII130 has been shown to reduce polyglutamine-induced cell loss m-Tyramine hydrobromide in cell culture (13, 18, 19). Many of these nuclear factors directly regulate histone acetylation or are in complexes that have acetylase activity. Also, a genetic screen in identified factors regulating acetylation as modifiers of polyglutamine-induced degeneration (20). Of the transcription factors implicated in m-Tyramine hydrobromide polyglutamine pathogenesis, we have focused on CBP, because it is usually a coactivator in important signal transduction pathways, for which it is functionally limiting (21). CBP is found in polyglutamine-positive inclusions in patient tissue and in mouse and cell culture models of polyglutamine disease (13, 15, 19, 22). Also, CBP-mediated transcription is usually impaired in the presence of mutant polyglutamine (13, 19). In this study, we examined the consequences of CBP disruption by expanded polyglutamine. We found that nuclear-targeted polyglutamine causes cell death that is mitigated by full-length CBP or its amino-terminal domain name alone. The cell death is usually associated with decreased histone acetylation and reduced by histone deacetylase inhibitors. These data implicate transcriptional dysfunction in polyglutamine toxicity and suggest the use of deacetylase inhibitors as therapeutic agents. Methods Cells and Plasmids. A mouse motor neuron-neuroblastoma Akt1 fusion cell line (MN-1) (23) was maintained in DMEM (Life Technologies, Bethesda, MD) supplemented with penicillin, streptomycin, glutamine, m-Tyramine hydrobromide and 10% FBS (Atlanta Biologicals, Norcross, GA). AR constructs encoding normal and expanded polyglutamine tracts (AR16 and AR110, respectively) were derived from pCMV-AR-HA (24), by (24, 26). Caspase-dependent formation of m-Tyramine hydrobromide a truncated fragment made up of the polyglutamine repeat is usually thought to be an important step in polyglutamine disease pathogenesis (27C29). For this project we restored an NLS to the truncated protein to recreate more accurately the normal localization of mutant AR. In addition, an amino terminal-enhanced GFP tag and a carboxyl-terminal myc tag were added for detection. Expression of these constructs in MN-1 cells caused repeat length-dependent cell death (Fig. ?(Fig.1).1). Expression peaked around 48 h after transfection, although it was still detectable at 96 h by Western blot and visually by GFP. Both anti-myc and anti-GFP antibodies detected comparable bands on Western blot, including an insoluble protein complex that remained in the stacking gel (Fig. ?(Fig.11(34). In our assay, SAHA was comparable to TSA in its ability to reduce cell death induced by AR110NLS ( 0.01) (Fig. ?(Fig.44 0.05), but only at the highest concentration of SAHA. SAHA increased histone acetylation in our cells at these concentrations (data not shown). Neither TSA nor SAHA caused morphological changes in the cells. We tested two other deacetylase inhibitors, sodium butyrate and PBA. These compounds, while inducing histone acetylation, have broader effects on gene expression than TSA. Mariadason (35) showed that sodium butyrate alters the expression of roughly 10 times as many genes as.