Limits...
dATF4 regulation of mitochondrial folate-mediated one-carbon metabolism is neuroprotective

View Article: PubMed Central - PubMed

ABSTRACT

Neurons rely on mitochondria as their preferred source of energy. Mutations in PINK1 and PARKIN cause neuronal death in early-onset Parkinson's disease (PD), thought to be due to mitochondrial dysfunction. In Drosophila pink1 and parkin mutants, mitochondrial defects lead to the compensatory upregulation of the mitochondrial one-carbon cycle metabolism genes by an unknown mechanism. Here we uncover that this branch is triggered by the activating transcription factor 4 (ATF4). We show that ATF4 regulates the expression of one-carbon metabolism genes SHMT2 and NMDMC as a protective response to mitochondrial toxicity. Suppressing Shmt2 or Nmdmc caused motor impairment and mitochondrial defects in flies. Epistatic analyses showed that suppressing the upregulation of Shmt2 or Nmdmc deteriorates the phenotype of pink1 or parkin mutants. Conversely, the genetic enhancement of these one-carbon metabolism genes in pink1 or parkin mutants was neuroprotective. We conclude that mitochondrial dysfunction caused by mutations in the Pink1/Parkin pathway engages ATF4-dependent activation of one-carbon metabolism as a protective response. Our findings show a central contribution of ATF4 signalling to PD that may represent a new therapeutic strategy. A video abstract for this article is available at https://youtu.be/cFJJm2YZKKM.

No MeSH data available.


Related in: MedlinePlus

In vivo suppression of Shmt2 or Nmdmc affects development and causes motor impairment in adult flies. (a) RNAi-mediated suppression of Shmt2 or Nmdmc. Expression levels were measured by real-time qPCR (mean±S.D.). The significant values relative to the control are indicated (asterisks, two-tailed unpaired t-test compared with Control). (b) Eclosion defects following RNAi-mediated suppression of Shmt2 or Nmdmc (asterisks, χ2 two-tailed, 95% confidence intervals). (c) Motor impairment upon RNAi-mediated suppression of Shmt2 or Nmdmc. Flies were tested using a standard climbing assay (mean±S.D.; asterisks, one-way ANOVA with Dunnett's multiple comparison test). (d) Decreased lifespan upon RNAi-mediated suppression of Shmt2 or Nmdmc. Fly viability was scored over a period of 90 days (n=165 for Control (left panel), n=68 for Shmt2 RNAi#1, n=108 for Shmt2 RNAi#2, n=143 for Control (right panel), n=116 for Nmdmc RNAi#1, n=102 for Nmdmc RNAi#2; asterisks, log-rank, Mantel-Cox test). (e) Coordinated changes in metabolite abundance on the downregulation of Shmt2 or Nmdmc. Canonical pathways altered in both Shmt2 and Nmdmc RNAi flies were analysed using the IPA Comparison Analysis tool. The heat map corresponds to the –log (P-value) for the canonical pathways significantly perturbed by the downregulation of either Shmt2 or Nmdmc (cutoff for P-value is 0.001 for both Shmt2 and Nmdmc RNAi data sets). Genotypes in (a–e): Control: daGAL4. All RNAi lines were driven by daGAL4
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5384021&req=5

fig3: In vivo suppression of Shmt2 or Nmdmc affects development and causes motor impairment in adult flies. (a) RNAi-mediated suppression of Shmt2 or Nmdmc. Expression levels were measured by real-time qPCR (mean±S.D.). The significant values relative to the control are indicated (asterisks, two-tailed unpaired t-test compared with Control). (b) Eclosion defects following RNAi-mediated suppression of Shmt2 or Nmdmc (asterisks, χ2 two-tailed, 95% confidence intervals). (c) Motor impairment upon RNAi-mediated suppression of Shmt2 or Nmdmc. Flies were tested using a standard climbing assay (mean±S.D.; asterisks, one-way ANOVA with Dunnett's multiple comparison test). (d) Decreased lifespan upon RNAi-mediated suppression of Shmt2 or Nmdmc. Fly viability was scored over a period of 90 days (n=165 for Control (left panel), n=68 for Shmt2 RNAi#1, n=108 for Shmt2 RNAi#2, n=143 for Control (right panel), n=116 for Nmdmc RNAi#1, n=102 for Nmdmc RNAi#2; asterisks, log-rank, Mantel-Cox test). (e) Coordinated changes in metabolite abundance on the downregulation of Shmt2 or Nmdmc. Canonical pathways altered in both Shmt2 and Nmdmc RNAi flies were analysed using the IPA Comparison Analysis tool. The heat map corresponds to the –log (P-value) for the canonical pathways significantly perturbed by the downregulation of either Shmt2 or Nmdmc (cutoff for P-value is 0.001 for both Shmt2 and Nmdmc RNAi data sets). Genotypes in (a–e): Control: daGAL4. All RNAi lines were driven by daGAL4

Mentions: To investigate the in vivo role of Shmt2 and Nmdmc, we determined the consequences of their suppression using RNAi (Figure 3a). The knockdown of Shmt2 or Nmdmc caused developmental defects characterized by a significant failure of eclosion (Figure 3b). Analysis of the eclosed adults revealed that the knockdown of Shmt2 or Nmdmc resulted in an impaired climbing ability, suggesting a locomotor deficit (Figure 3c), and decreased lifespan (Figure 3d). The knockdown of either Shmt2 or Nmdmc led to significant metabolic changes in several canonical pathways, most significantly those related to nucleotide degradation and salvage (Figure 3e and Supplementary Table 2). To further determine whether the consequences of Shmt2 or Nmdmc knockdown were linked to mitochondrial defects, we performed a morphological and functional analysis of mitochondria. This revealed a fragmented mitochondrial network (Figures 4a and b) that was associated with a loss of mitochondrial membrane potential (Δψm) in adult brain (Figures 4c and d) as well as a generalized loss of mitochondrial proteins (Figure 4e). In addition, Nmdmc knockdown adult flies exhibited an abnormal downturned wing posture (Figure 4f) and ultrastructural analysis of their indirect flight muscles revealed mitochondria with fragmented cristae (Figure 4g).


dATF4 regulation of mitochondrial folate-mediated one-carbon metabolism is neuroprotective
In vivo suppression of Shmt2 or Nmdmc affects development and causes motor impairment in adult flies. (a) RNAi-mediated suppression of Shmt2 or Nmdmc. Expression levels were measured by real-time qPCR (mean±S.D.). The significant values relative to the control are indicated (asterisks, two-tailed unpaired t-test compared with Control). (b) Eclosion defects following RNAi-mediated suppression of Shmt2 or Nmdmc (asterisks, χ2 two-tailed, 95% confidence intervals). (c) Motor impairment upon RNAi-mediated suppression of Shmt2 or Nmdmc. Flies were tested using a standard climbing assay (mean±S.D.; asterisks, one-way ANOVA with Dunnett's multiple comparison test). (d) Decreased lifespan upon RNAi-mediated suppression of Shmt2 or Nmdmc. Fly viability was scored over a period of 90 days (n=165 for Control (left panel), n=68 for Shmt2 RNAi#1, n=108 for Shmt2 RNAi#2, n=143 for Control (right panel), n=116 for Nmdmc RNAi#1, n=102 for Nmdmc RNAi#2; asterisks, log-rank, Mantel-Cox test). (e) Coordinated changes in metabolite abundance on the downregulation of Shmt2 or Nmdmc. Canonical pathways altered in both Shmt2 and Nmdmc RNAi flies were analysed using the IPA Comparison Analysis tool. The heat map corresponds to the –log (P-value) for the canonical pathways significantly perturbed by the downregulation of either Shmt2 or Nmdmc (cutoff for P-value is 0.001 for both Shmt2 and Nmdmc RNAi data sets). Genotypes in (a–e): Control: daGAL4. All RNAi lines were driven by daGAL4
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384021&req=5

fig3: In vivo suppression of Shmt2 or Nmdmc affects development and causes motor impairment in adult flies. (a) RNAi-mediated suppression of Shmt2 or Nmdmc. Expression levels were measured by real-time qPCR (mean±S.D.). The significant values relative to the control are indicated (asterisks, two-tailed unpaired t-test compared with Control). (b) Eclosion defects following RNAi-mediated suppression of Shmt2 or Nmdmc (asterisks, χ2 two-tailed, 95% confidence intervals). (c) Motor impairment upon RNAi-mediated suppression of Shmt2 or Nmdmc. Flies were tested using a standard climbing assay (mean±S.D.; asterisks, one-way ANOVA with Dunnett's multiple comparison test). (d) Decreased lifespan upon RNAi-mediated suppression of Shmt2 or Nmdmc. Fly viability was scored over a period of 90 days (n=165 for Control (left panel), n=68 for Shmt2 RNAi#1, n=108 for Shmt2 RNAi#2, n=143 for Control (right panel), n=116 for Nmdmc RNAi#1, n=102 for Nmdmc RNAi#2; asterisks, log-rank, Mantel-Cox test). (e) Coordinated changes in metabolite abundance on the downregulation of Shmt2 or Nmdmc. Canonical pathways altered in both Shmt2 and Nmdmc RNAi flies were analysed using the IPA Comparison Analysis tool. The heat map corresponds to the –log (P-value) for the canonical pathways significantly perturbed by the downregulation of either Shmt2 or Nmdmc (cutoff for P-value is 0.001 for both Shmt2 and Nmdmc RNAi data sets). Genotypes in (a–e): Control: daGAL4. All RNAi lines were driven by daGAL4
Mentions: To investigate the in vivo role of Shmt2 and Nmdmc, we determined the consequences of their suppression using RNAi (Figure 3a). The knockdown of Shmt2 or Nmdmc caused developmental defects characterized by a significant failure of eclosion (Figure 3b). Analysis of the eclosed adults revealed that the knockdown of Shmt2 or Nmdmc resulted in an impaired climbing ability, suggesting a locomotor deficit (Figure 3c), and decreased lifespan (Figure 3d). The knockdown of either Shmt2 or Nmdmc led to significant metabolic changes in several canonical pathways, most significantly those related to nucleotide degradation and salvage (Figure 3e and Supplementary Table 2). To further determine whether the consequences of Shmt2 or Nmdmc knockdown were linked to mitochondrial defects, we performed a morphological and functional analysis of mitochondria. This revealed a fragmented mitochondrial network (Figures 4a and b) that was associated with a loss of mitochondrial membrane potential (Δψm) in adult brain (Figures 4c and d) as well as a generalized loss of mitochondrial proteins (Figure 4e). In addition, Nmdmc knockdown adult flies exhibited an abnormal downturned wing posture (Figure 4f) and ultrastructural analysis of their indirect flight muscles revealed mitochondria with fragmented cristae (Figure 4g).

View Article: PubMed Central - PubMed

ABSTRACT

Neurons rely on mitochondria as their preferred source of energy. Mutations in PINK1 and PARKIN cause neuronal death in early-onset Parkinson's disease (PD), thought to be due to mitochondrial dysfunction. In Drosophila pink1 and parkin mutants, mitochondrial defects lead to the compensatory upregulation of the mitochondrial one-carbon cycle metabolism genes by an unknown mechanism. Here we uncover that this branch is triggered by the activating transcription factor 4 (ATF4). We show that ATF4 regulates the expression of one-carbon metabolism genes SHMT2 and NMDMC as a protective response to mitochondrial toxicity. Suppressing Shmt2 or Nmdmc caused motor impairment and mitochondrial defects in flies. Epistatic analyses showed that suppressing the upregulation of Shmt2 or Nmdmc deteriorates the phenotype of pink1 or parkin mutants. Conversely, the genetic enhancement of these one-carbon metabolism genes in pink1 or parkin mutants was neuroprotective. We conclude that mitochondrial dysfunction caused by mutations in the Pink1/Parkin pathway engages ATF4-dependent activation of one-carbon metabolism as a protective response. Our findings show a central contribution of ATF4 signalling to PD that may represent a new therapeutic strategy. A video abstract for this article is available at https://youtu.be/cFJJm2YZKKM.

No MeSH data available.


Related in: MedlinePlus