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PERK inhibition prevents tau-mediated neurodegeneration in a mouse model of frontotemporal dementia.

Radford H, Moreno JA, Verity N, Halliday M, Mallucci GR - Acta Neuropathol. (2015)

Bottom Line: The PERK-eIF2α branch of the Unfolded Protein Response (UPR) mediates the transient shutdown of translation in response to rising levels of misfolded proteins in the endoplasmic reticulum.These are all characterised by the accumulation of misfolded disease-specific proteins in the brain in association with specific patterns of neuronal loss, but the role of UPR activation in their pathogenesis is unclear.Critically, restoring vital neuronal protein synthesis rates by inhibiting the PERK-eIF2α pathway, both genetically and pharmacologically, prevents prion neurodegeneration downstream of misfolded prion protein accumulation.

View Article: PubMed Central - PubMed

Affiliation: MRC Toxicology Unit, Hodgkin Building, University of Leicester, Lancaster Road, Leicester, LE1 9HN, UK.

ABSTRACT
The PERK-eIF2α branch of the Unfolded Protein Response (UPR) mediates the transient shutdown of translation in response to rising levels of misfolded proteins in the endoplasmic reticulum. PERK and eIF2α activation are increasingly recognised in postmortem analyses of patients with neurodegenerative disorders, including Alzheimer's disease, the tauopathies and prion disorders. These are all characterised by the accumulation of misfolded disease-specific proteins in the brain in association with specific patterns of neuronal loss, but the role of UPR activation in their pathogenesis is unclear. In prion-diseased mice, overactivation of PERK-P/eIF2α-P signalling results in the sustained reduction in global protein synthesis, leading to synaptic failure, neuronal loss and clinical disease. Critically, restoring vital neuronal protein synthesis rates by inhibiting the PERK-eIF2α pathway, both genetically and pharmacologically, prevents prion neurodegeneration downstream of misfolded prion protein accumulation. Here we show that PERK-eIF2α-mediated translational failure is a key process leading to neuronal loss in a mouse model of frontotemporal dementia, where the misfolded protein is a form of mutant tau. rTg4510 mice, which overexpress the P301L tau mutation, show dysregulated PERK signalling and sustained repression of protein synthesis by 6 months of age, associated with onset of neurodegeneration. Treatment with the PERK inhibitor, GSK2606414, from this time point in mutant tau-expressing mice restores protein synthesis rates, protecting against further neuronal loss, reducing brain atrophy and abrogating the appearance of clinical signs. Further, we show that PERK-eIF2α activation also contributes to the pathological phosphorylation of tau in rTg4510 mice, and that levels of phospho-tau are lowered by PERK inhibitor treatment, providing a second mechanism of protection. The data support UPR-mediated translational failure as a generic pathogenic mechanism in protein-misfolding disorders, including tauopathies, that can be successfully targeted for prevention of neurodegeneration.

No MeSH data available.


Related in: MedlinePlus

PERK inhibitor treatment reduces eIF2α-P and ATF4 protein levels and restores protein synthesis rates in mutant tau-expressing rTg4510 mice. a tauP301L+ mice were treated twice daily by oral gavage from 6 months with either the PERK inhibitor, GSK2606414 50 mg/kg, (blue bars) or vehicle (grey bars) and tested at 8 months of age. b Immunostaining showed a significant reduction in PERK-P (red) and pSer202/Thr205-tau (AT8, green) staining in the hippocampus after GSK2606414 treatment. Graphs show quantification of relative intensity for PERK-P and ptau compared to transgene-negative mice (n = 3–5 mice, scale bar 20 μm). c PERK inhibitor treatment markedly reduced PERK-P, eIF2α-P and ATF4 protein levels in 8-month-old tauP301L+ mice, preventing the decline of global protein synthesis rates as determined by 35S-methionine incorporation into protein (d) in comparison to vehicle-treated animals (n = 3 mice). Representative immunoblots of hippocampal lysates and bar charts quantitating protein levels (in three independent samples). All bar charts show mean ± SEM, *p < 0.05, **p < 0.01, using Student’s t test.
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Fig2: PERK inhibitor treatment reduces eIF2α-P and ATF4 protein levels and restores protein synthesis rates in mutant tau-expressing rTg4510 mice. a tauP301L+ mice were treated twice daily by oral gavage from 6 months with either the PERK inhibitor, GSK2606414 50 mg/kg, (blue bars) or vehicle (grey bars) and tested at 8 months of age. b Immunostaining showed a significant reduction in PERK-P (red) and pSer202/Thr205-tau (AT8, green) staining in the hippocampus after GSK2606414 treatment. Graphs show quantification of relative intensity for PERK-P and ptau compared to transgene-negative mice (n = 3–5 mice, scale bar 20 μm). c PERK inhibitor treatment markedly reduced PERK-P, eIF2α-P and ATF4 protein levels in 8-month-old tauP301L+ mice, preventing the decline of global protein synthesis rates as determined by 35S-methionine incorporation into protein (d) in comparison to vehicle-treated animals (n = 3 mice). Representative immunoblots of hippocampal lysates and bar charts quantitating protein levels (in three independent samples). All bar charts show mean ± SEM, *p < 0.05, **p < 0.01, using Student’s t test.

Mentions: rTg4510 tauP301L+ mice received 50 mg/kg GSK2606414 (n = 10) or vehicle (n = 8) by oral gavage twice daily, a dose optimised for good levels of brain penetration, as described in [23], for 2 months (Fig. 2a). At this time point, at 8 months of age, animals were killed for analysis. As predicted, and consistent with previous observations in prion-diseased mice [23], GSK2606414 treatment significantly reduced levels of PERK-P, eIF2α-P and ATF4 levels in tauP301L+ mice, compared to vehicle-treated animals, which showed persistently elevated of levels of these proteins (Fig. 2b, c). Critically, PERK inhibitor treatment restored global protein synthesis rates to normal in 8-month-old tauP301L+ mice, in contrast to vehicle-treated animals, which showed markedly reduced translation rates at this time point (Fig. 2d). (GSK2606414 does not affect eIF2α-P levels and global protein synthesis where the UPR is not activated [23]).Fig. 2


PERK inhibition prevents tau-mediated neurodegeneration in a mouse model of frontotemporal dementia.

Radford H, Moreno JA, Verity N, Halliday M, Mallucci GR - Acta Neuropathol. (2015)

PERK inhibitor treatment reduces eIF2α-P and ATF4 protein levels and restores protein synthesis rates in mutant tau-expressing rTg4510 mice. a tauP301L+ mice were treated twice daily by oral gavage from 6 months with either the PERK inhibitor, GSK2606414 50 mg/kg, (blue bars) or vehicle (grey bars) and tested at 8 months of age. b Immunostaining showed a significant reduction in PERK-P (red) and pSer202/Thr205-tau (AT8, green) staining in the hippocampus after GSK2606414 treatment. Graphs show quantification of relative intensity for PERK-P and ptau compared to transgene-negative mice (n = 3–5 mice, scale bar 20 μm). c PERK inhibitor treatment markedly reduced PERK-P, eIF2α-P and ATF4 protein levels in 8-month-old tauP301L+ mice, preventing the decline of global protein synthesis rates as determined by 35S-methionine incorporation into protein (d) in comparison to vehicle-treated animals (n = 3 mice). Representative immunoblots of hippocampal lysates and bar charts quantitating protein levels (in three independent samples). All bar charts show mean ± SEM, *p < 0.05, **p < 0.01, using Student’s t test.
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Fig2: PERK inhibitor treatment reduces eIF2α-P and ATF4 protein levels and restores protein synthesis rates in mutant tau-expressing rTg4510 mice. a tauP301L+ mice were treated twice daily by oral gavage from 6 months with either the PERK inhibitor, GSK2606414 50 mg/kg, (blue bars) or vehicle (grey bars) and tested at 8 months of age. b Immunostaining showed a significant reduction in PERK-P (red) and pSer202/Thr205-tau (AT8, green) staining in the hippocampus after GSK2606414 treatment. Graphs show quantification of relative intensity for PERK-P and ptau compared to transgene-negative mice (n = 3–5 mice, scale bar 20 μm). c PERK inhibitor treatment markedly reduced PERK-P, eIF2α-P and ATF4 protein levels in 8-month-old tauP301L+ mice, preventing the decline of global protein synthesis rates as determined by 35S-methionine incorporation into protein (d) in comparison to vehicle-treated animals (n = 3 mice). Representative immunoblots of hippocampal lysates and bar charts quantitating protein levels (in three independent samples). All bar charts show mean ± SEM, *p < 0.05, **p < 0.01, using Student’s t test.
Mentions: rTg4510 tauP301L+ mice received 50 mg/kg GSK2606414 (n = 10) or vehicle (n = 8) by oral gavage twice daily, a dose optimised for good levels of brain penetration, as described in [23], for 2 months (Fig. 2a). At this time point, at 8 months of age, animals were killed for analysis. As predicted, and consistent with previous observations in prion-diseased mice [23], GSK2606414 treatment significantly reduced levels of PERK-P, eIF2α-P and ATF4 levels in tauP301L+ mice, compared to vehicle-treated animals, which showed persistently elevated of levels of these proteins (Fig. 2b, c). Critically, PERK inhibitor treatment restored global protein synthesis rates to normal in 8-month-old tauP301L+ mice, in contrast to vehicle-treated animals, which showed markedly reduced translation rates at this time point (Fig. 2d). (GSK2606414 does not affect eIF2α-P levels and global protein synthesis where the UPR is not activated [23]).Fig. 2

Bottom Line: The PERK-eIF2α branch of the Unfolded Protein Response (UPR) mediates the transient shutdown of translation in response to rising levels of misfolded proteins in the endoplasmic reticulum.These are all characterised by the accumulation of misfolded disease-specific proteins in the brain in association with specific patterns of neuronal loss, but the role of UPR activation in their pathogenesis is unclear.Critically, restoring vital neuronal protein synthesis rates by inhibiting the PERK-eIF2α pathway, both genetically and pharmacologically, prevents prion neurodegeneration downstream of misfolded prion protein accumulation.

View Article: PubMed Central - PubMed

Affiliation: MRC Toxicology Unit, Hodgkin Building, University of Leicester, Lancaster Road, Leicester, LE1 9HN, UK.

ABSTRACT
The PERK-eIF2α branch of the Unfolded Protein Response (UPR) mediates the transient shutdown of translation in response to rising levels of misfolded proteins in the endoplasmic reticulum. PERK and eIF2α activation are increasingly recognised in postmortem analyses of patients with neurodegenerative disorders, including Alzheimer's disease, the tauopathies and prion disorders. These are all characterised by the accumulation of misfolded disease-specific proteins in the brain in association with specific patterns of neuronal loss, but the role of UPR activation in their pathogenesis is unclear. In prion-diseased mice, overactivation of PERK-P/eIF2α-P signalling results in the sustained reduction in global protein synthesis, leading to synaptic failure, neuronal loss and clinical disease. Critically, restoring vital neuronal protein synthesis rates by inhibiting the PERK-eIF2α pathway, both genetically and pharmacologically, prevents prion neurodegeneration downstream of misfolded prion protein accumulation. Here we show that PERK-eIF2α-mediated translational failure is a key process leading to neuronal loss in a mouse model of frontotemporal dementia, where the misfolded protein is a form of mutant tau. rTg4510 mice, which overexpress the P301L tau mutation, show dysregulated PERK signalling and sustained repression of protein synthesis by 6 months of age, associated with onset of neurodegeneration. Treatment with the PERK inhibitor, GSK2606414, from this time point in mutant tau-expressing mice restores protein synthesis rates, protecting against further neuronal loss, reducing brain atrophy and abrogating the appearance of clinical signs. Further, we show that PERK-eIF2α activation also contributes to the pathological phosphorylation of tau in rTg4510 mice, and that levels of phospho-tau are lowered by PERK inhibitor treatment, providing a second mechanism of protection. The data support UPR-mediated translational failure as a generic pathogenic mechanism in protein-misfolding disorders, including tauopathies, that can be successfully targeted for prevention of neurodegeneration.

No MeSH data available.


Related in: MedlinePlus