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Loss of pex5 sensitizes zebrafish to fasting due to deregulated mitochondria, mTOR, and autophagy

ABSTRACT: Animal models have been utilized to understand the pathogenesis of Zellweger spectrum disorders (ZSD), but the link between the clinical manifestations and molecular pathways has not yet been clearly established. We generated a peroxin 5 homozygous mutant zebrafish (pex5-/-) to gain insight into the molecular pathogenesis of peroxisome dysfunction. pex5-/- displays hallmarks of ZSD in humans and die within one month after birth. Fasting rapidly depletes the liver lipids and glycogen in pex5-/- and expedites their mortality. Mechanistically, abnormal mitochondrial activity and mechanistic target of rapamycin (mTOR) signaling act together to induce metabolic alterations to deplete the hepatic nutrients and accumulate the damaged mitochondria. Accordingly, the use of chemical interventions blocking either the mitochondrial activities or the mechanistic target of rapamycin complex 1 or a combination of both improves the metabolic imbalance shown in the fasted pex5-/- livers and extends the survival of the animals. Furthermore, the use of an autophagy activator also effectively ameliorated the early mortality of the fasted pex5-/-. These results suggest that fasting may be detrimental to patients with peroxisome dysfunction and that modulating the mitochondria, mTOR, or autophagy activities may provide a therapeutic option to alleviate the symptoms of peroxisomal diseases associated with metabolic dysfunction.

ORGANISM(S): Danio rerio

PROVIDER: GSE205349 | GEO | 2022/06/05

REPOSITORIES: GEO

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Project description:Peroxisome biogenesis diseases (PBDs) are characterized by global defects in peroxisomal function and can result in severe brain, liver, kidney, and bone malfunctions. PBDs are due to mutations in peroxisome biogenesis factors (PEX genes) that are responsible for peroxisome assembly and function. Increasing evidence suggests that peroxisome import functions decline during aging. However, the transcriptome profiling of peroxisome import defects and how they affect disease development are still lacking. PEX5 encodes the cytoplasmic receptors for peroxisome-targeting signal types 1. We generate knock-in human HEK293 cells mutant using CRISPR to transiently express PEX5 cysteine 11 to alanine mutant (PEX5C11A), which blocks PEX5 recycling and exerts dominant negative effect on PEX5 mediated peroxisome import. To identify conserved responses, we perform transcriptomic analysis on Drosophila oenocyte-specific Pex1, Pex12 and Pex5 knockdowns and on human cells with impaired peroxisome import (through expressing PEX5C11A and applying PEX5 siRNA respectively). PEX5C11A induction triggers vast transcriptomic changes, including decreased oxidative phosphorylation, increased MAPK signaling and HIPPO signaling. PEX5 siRNA specifically decreases spliceosome activity and increases cholesterol metabolism. Using gene set enrichment analysis (GSEA), we identify protein processing in endoplasmic reticulum pathway, specifically ER-associated protein degradation (ERAD) pathway is induced in all PEX knockdowns in Drosophila. Peroxisome dysfunction elevates eIF2α phosphorylation in both Drosophila and human cell culture independent of XBP1 activation, suggesting increased integrative stress response (ISR). Moreover, peroxisome stress decreases ribosome biogenesis genes and impairs ribosome biogenesis in flies and human cells. Specifically, peroxisome stress impairs the 5'-ETS cleavage activity during the ribosome biogenesis and dampens 40S small ribosomal export in both flies and human. Our results suggest that reduced ribosome biogenesis and elevated ISR could be conserved cellular response to peroxisome import stress.

Project description:Although mitochondrial dysfunctions are implicated in the pathogenesis of obesity, the molecular mechanisms underlying obesity-related metabolic abnormalities are still not well established. To acquire a comprehensive picture of mitochondrial molecular changes within metabolically active tissues, we focused on hepatic and muscle whole cellular transcriptome and mitochondrial proteome alterations in 16 and 48 weeks old high fat diet (HFD)-feed wild type C57BL/6J and hyperphagic, genetically modified mice with leptin dysfunction (ob/ob and db/db). On transcriptome level, the most discriminative hepatic alterations distinguished between genetically modified and wild type mice, and between overnight fasted and non-fasted mice, while the muscle transcriptional alterations related mainly to the fasting state. The fractions of uniquely different proteins were consistently higher in hyperphagic than in HFD-fed mice and in fasted than non-fasted mice . The liver samples revealed overall higher number of differentially expressed RNAs and proteins than muscle samples. Differentially expressed genes and proteins in the liver, but not in the muscle, could be assigned to several Gene Ontology terms, including oxidation-reduction and several metabolic processes. Thus, altered expression of genes and proteins accompanied the state of obesity and was quantitatively different in the liver and muscle. Our parallel microarray- and quantitative mitochondrial mass spectrometry-based study performed on hepatic and muscle samples identified a higher number of differentially expressed proteins than any other studies investigating obesity-related proteomes. However, even with our integrated transcriptomic and proteomic approach still many details and dynamics of a chain of metabolic events leading to obesity-related mitochondrial dysfunctions remain unresolved . 48 samples each of liver and muscle (total samples: 96). Samples splitted equally according to 3 criterions: age (24 young/24 old), fasting status (24 fasted/24 non fasted), and strain+diet (12 each: B6.V-Lep ob/J+D12450B, B6.BKS(D)-Lep rdb/J+D12450B, C57BL/6J+D12450B, C57BL/6J+D12492). Overall 3 replicates for each strain+diet/age/fasting_status combination. Low fat diet = D12450B; high fat diet = D12492.

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Loss of pex5 sensitizes zebrafish to fasting due to deregulated mitochondria, mTOR, and autophagy

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