Effect of TRAP1 mutation on modification of [A53T]α-Synuclein toxicity.

<p>(A) Western blot analysis of HEK293 lysates transfected with indicated constructs showed similar expression levels of TRAP1[WT] and TRAP1[D158N] and a reduction of endogenous TRAP1 by siTRAP1. Blot was probed with TRAP1-specific antibody. ß-Actin served as loading control. (B, C) Effect of TRAP1[WT] and TRAP1[D158N] on [A53T]α-Synuclein-induced effects in HEK293 cells. (B) Effect of TRAP1[D158N] on [A53T]α-Synuclein-induced toxicity. Cell survival after rotenone (200 µM) treatment was monitored. Compared to TRAP1[WT], cells expressing TRAP1[D158N] displayed a significant reduction in survival (t-test, **p<0.01). (C) Assessment of ATP production via Complex I in unstressed cells with [A53T]α-Synuclein expression revealed a significant reduction of ATP levels in TRAP1[D158N] versus TRAP1[WT] expressing cells (t-test, ***p<0.001).</p

[A53T]α-Synuclein expression in fly heads results in age-dependent loss of DA.

<p>(A) Western blot showing abundance of human [A53T]α-Synuclein after aminergic neuron (<i>ddc-GAL4</i>)-specific expression in lysates of fly heads. While flies without [A53T]α-Synuclein transgene do not show any detectable signal for [A53T]α-Synuclein in Western blot, an increase of [A53T]α-Synuclein protein levels was observed by increasing the copy number of transgenes. Syntaxin served as a loading control and molecular weight markers are indicated. (B) Whereas <i>ddc>A53T/+</i> flies displayed no significant difference in longevity as compared to <i>ddc/+</i> flies, flies homozygous for <i>ddc>A53T</i> showed a significant decrease (p<0.001, Log rank test). (C) Compared to controls (<i>ddc/+</i>), <i>ddc>A53T</i>/+ flies showed a significant age-dependent loss of DA at 3 and 4 weeks post eclosion (*p<0.05 vs. control). (D) Only <i>ddc>A53T</i> flies showed a significant decrease (***p<0.001) in DA concentration in fly heads at 4 weeks. Comparisons of multiple controls were not significant (4 week values as per cent of 1 week values; ANOVA followed by Newman-Keuls Multiple Comparison Test).</p

Alterations in TRAP1 levels influence [A53T]α-Synuclein-induced sensitivity to oxidative stress and mitochondrial effects in HEK293 cells.

<p>HEK293 cells were transfected with plasmids promoting [A53T]α-Synuclein or TRAP1 expression. Empty vector transfection served as control. In addition, RNAi-mediated silencing of endogenous TRAP1 was induced (siTRAP1). Cells transfected with indicated plasmid combinations were treated with (A) hydrogen peroxide (100 µm) or (B) rotenone (200 µM) to induce oxidative stress. Cell numbers were analyzed to monitor survival. (C–E) HEK293 without oxidative stress treatment overexpressing the indicated proteins, or with RNAi-mediated silencing of TRAP1 were analyzed for (C) ATP production via Complex I, (D) total ATP content, and (E) mitochondrial membrane potential. Statistical analysis of displayed bar graphs was performed using ANOVA followed by Newman-Keuls Multiple Comparison Test. (A, B) Biologically relevant comparisons are indicated in bar graphs. (C) Differences compared to control are indicated. (A, B, C) A detailed summary of all comparisons is summarized in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002488#pgen.1002488.s008" target="_blank">Figure S8</a>. (D, E) Only cells with [A53T]α-Synuclein expression and TRAP1 reduction displayed significant differences in statistical analysis as indicated in graph. All other comparisons were not significant. *p<0.05; **p<0.01; ***p<0.001; ns = not significant.</p

Analysis of polyQ aggregate load.

<p>(<b>A</b>) Exemplified filter retardation analysis to visualize polyQ aggregates. Decreasing amounts of loaded protein derived from fly heads of control (<i>GMR-GAL4</i>, top), <i>GMR>polyQ</i> (middle) or <i>GMR>polyQ</i> in combination with a candidate suppressor (bottom). (<b>B</b>) Densitometric measures of filter retardation analysis. Data depicted as fold change compared to control (<i>GMR>polyQ</i>) for suppressors and enhancers of polyQ-induced toxicity. Independent homogenates (if available) were used for repetitions. In case of none or only one independent repetition n≤2 is indicated. In all other cases, number of independent repetitions is n≥3. Significant changes are indicated * p<0.05; *** p<0.001.</p

Screening for modifiers of polyQ-induced toxicity.

<p>(<b>A</b>) Rough eye phenotype (REP) used as a primary readout for screening. Compared to control (upper panels), eye-specific (<i>GMR-GAL4</i>) expression of polyQ (lower panels) induces disturbances of the external eye texture, e. g. depigmentation of the compound eye observed by light microscopy (left) and as depicted in scanning electron micrographs (middle). Toluidine blue-stained semi-thin eye sections reveal that the disturbance of external eye structures is accompanied by degeneration of retinal cells (right). (<b>B</b>) Modification of the polyQ-induced REP by enhancers and suppressors. VDRC transformants used to silence respective genes: <i>CG3284</i> (11219), <i>CG16807</i> (23843), <i>CG15399</i> (19450) and <i>CG7843</i> (22574). (<b>C</b>) Flow chart of the screening procedures to identify modifiers of polyQ-induced toxicity. (<b>D</b>) Brief summary of screen results. Scale bars represent either 200 µm in eye pictures or 50 µm in semi-thin eye sections.</p

TRAP1 overexpression protects rat cortical neurons from [A53T]α-Synuclein-induced sensitivity to rotenone.

<p>(A) Western blot analysis of cells infected with lentivirus promoting either GFP, TRAP1 or [A53T]α-Synuclein expression. For visualization, the blot was probed with either TRAP1- or α-Synuclein-specific antibodies, respectively. ß-Actin was used for normalization. (B) Rat cortical neurons infected with lentivirus promoting GFP expression were stained for neuronal marker NeuN (red) and DNA (Hoechst, blue). A high percentage of cells showed co-localization between GFP and the neuronal marker NeuN, indicative for high infection efficacy. Scale bar indicates 43 µm. (C) Quantification of cell survival after 16 h of rotenone treatment of cells infected with viruses mediating expression of indicated protein. Significant differences compared to control (GFP) are indicated. All other comparisons revealed highly significant differences (p<0.001) in statistical analysis (ANOVA followed by Newman-Keuls Multiple Comparison Test). **p<0.01; ***p<0.001; ns = not significant.</p

TRAP1 overexpression mitigates detrimental effects induced by neuronal [A53T]α-Synuclein expression.

<p>(A) Overexpression of [A53T]α-Synuclein under control of <i>ddc-GAL4</i> resulted in reduction of DA in fly heads at 4 weeks, which was potentiated by TRAP1 deficiency (<i>TRAP1[KG]/+;ddc>A53T/+</i>), but mitigated by TRAP1 overexpression (<i>ddc>A53T/hTRAP1</i>). (B) <i>ddc>A53T</i> flies display a reduction of TH-positive neurons, which was potentiated by TRAP1 deficiency, but rescued to control levels by TRAP1 overexpression. (C) In negative geotaxis assays <i>ddc>A53T</i> flies displayed a time-dependent decline in locomotion. Reduction of TRAP1 enhanced the inability to climb (although not significant), while overexpression of hTRAP1 provided a significant rescue effect (comparison of <i>ddc>A53T/+</i> vs <i>ddc>A53T/hTRAP1</i> at 4 weeks: p<0.05). Statistics in (A, B): ANOVA followed by Newman-Keuls Multiple Comparison Test; (C): 2-way ANOVA followed by Bonferroni post-hoc tests. Displayed are biologically relevant comparisons. *p<0.05; **p<0.01; ***p<0.001; ns = not significant. (D) Alterations in TRAP1 levels did not influence PolyQ-induced rough eye phenotypes. Light micrographs of external eye structures show that PolyQ-induced REP was suppressed by parallel expression of HSP70. In contrast, neither overexpression of hTRAP1 or silencing of endogenous TRAP1 by RNAi had an obvious impact on external eye structure. Expression of mitochondrial localized GFP (mito-GFP) served as control.</p

List of unspecific modifiers of polyQ-induced toxicity.

<p>Table lists gene name (if applicable) and gene ID of all candidates identified to have a similar effect on polyQ- and Tau-induced REPs. Mode of modification is indicated (enhancement (E), suppression (S)). A brief summary of the molecular and biological functions assigned to the identified gene products is listed.</p

Overlap between screens for genetic modifiers of polyQ-induced toxicity or aggregation.

<p>The Venn-like diagram displays only candidate genes shared by the different screens. Mode of modification (enhancement/suppression) is not addressed, due to the different readouts (aggregation/toxicity), model systems (<i>Drosophila</i>, insect cells, <i>C. elegans</i>) and elongated polyQ-containing proteins used in the diverse screening approaches.</p

Computational analysis of modifiers of polyQ-induced toxicity.

<p>(<b>A</b>) Meta-interaction network displaying modifiers of polyQ toxicity. Only candidates causing a robust modification of the REP (red) as well as directly interacting subtle modifiers (black) were retained from an initial network of more than 5 k genes with 20 k interactions <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047452#pone.0047452-Costello1" target="_blank">[32]</a>. One local cluster of functionally interacting modifiers is highlighted. (<b>B</b>) Gene Ontology analysis of these candidate gene groups. Shown are -log₁₀(p-value) scores for GO term enrichment for candidate gene groups (horizontal axis, see inset for group identities) and GO term (vertical). The matrix incorporates the structure of the GO hierarchy and is based on the Topology Weighted Term-algorithm as implemented in Ontologizer (terms with a p-value<0.005 are shown).</p