Project description:Mitochondrial dysfunction, disruption of F-actin polymerization, and transcriptomic alterations in zebrafish larvae exposed to trichloroethylene
Project description:The pesticide fipronil affects transcriptional networks related to mitochondrial dysfunction and methylation in zebrafish embryos (Danio rerio)
Project description:Protein misfolding and aggregation deregulate the proteostasis network and are hallmarks of cell degeneration processes associated with aging and human diseases. But how proteome aggregation causes cell degeneration remains controversial due to the lack of suitable methods for controlling proteome aggregation at the cellular and organismal levels. To overcome this limitation, we have generated zebrafish embryos that exhibit protein aggregation due to misincorporation of Serine (Ser) at non-cognate protein sites on a proteome wide scale. These mistranslating embryos display up regulation of the unfolded protein response (UPR) and the ubiquitin proteasome pathway (UPP), increased protein ubiquitination and down-regulation of protein biosynthesis. Proteome damage also induces major disruption of the mitochondrial network, accompanied by mitochondrial and nuclear DNA damage and accumulation of reactive oxygen species (ROS). Taken together, our data highlight important roles of gene translational accuracy in the maintenance of ER homeostasis, DNA damage, mitochondrial function and oxidative stress. We postulate that protein biosynthesis errors (PBE) contribute to proteome aggregation and are a main cause of mitochondrial disruption.
Project description:In mammals, retinal damage is followed by Müller glia cell activation and proliferation. While retinal gliosis persists in adult mammals after an insult or disease, some vertebrates, including zebrafish, have the capacity to regenerate. We believe we are the first group to show that gliosis is a fibrotic-like process in mammals’ eyes caused by differential activation of canonical and non-canonical TGFβ signaling pathways.
Project description:A loss of the checkpoint kinase ATM leads to impairments in the DNA damage response, and in humans causes cerebellar neurodegeneration, and a high risk to cancer. A loss of ATM is also associated with increased protein aggregation. The relevance and characteristics of this aggregation are still incompletely understood. Moreover, it is unclear to what extent other genotoxic conditions can trigger protein aggregation as well. Here, we show that targeting ATM, but also ATR or DNA topoisomerases result in a similar, widespread aggregation of a metastable, disease-associated subfraction of the proteome. Aggregation-prone model substrates, including expanded polyglutamine repeats, aggregate faster under these conditions. This increased aggregation results from an overload of chaperone systems, which lowers the cell-intrinsic threshold for proteins to aggregate. In line with this, we find that inhibition of the HSP70 chaperone system further exacerbates the increased protein aggregation. Moreover, we identify the molecular chaperone HSPB5 as a potent suppressor of it. Our findings reveal that various genotoxic conditions trigger protein aggregation, in a manner that is highly reminiscent of the widespread aggregation occurring in situations of proteotoxic stress and in proteinopathies.
Project description:Mutations in CHCHD10, a mitochondrial protein with undefined functions, are associated with autosomal dominant mitochondrial diseases. Chchd10 knock-in mice harboring a heterozygous S55L mutation (equivalent to human pathogenic S59L) develop a fatal mitochondrial cardiomyopathy caused by CHCHD10 aggregation and proteotoxic mitochondrial integrated stress response (mtISR). In mutant hearts, mtISR is accompanied by a metabolic rewiring characterized by increased reliance on glycolysis rather than fatty acid oxidation. To counteract this metabolic rewiring, heterozygous S55L mice were subjected to chronic high fat diet (HFD) to decrease insulin sensitivity and glucose uptake and enhance fatty acid utilization in the heart. HFD ameliorated the ventricular dysfunction of mutant hearts and significantly extended the survival of mutant female mice affected by severe pregnancy-induced cardiomyopathy. Gene expression profiles confirmed that HFD increased fatty acid utilization and ameliorated cardiomyopathy markers. Importantly, HFD also decreased accumulation of aggregated CHCHD10 in the S55L heart, suggesting activation of quality control mechanisms. Overall, our findings indicate that metabolic therapy can be effective in mitochondrial cardiomyopathies associated with proteotoxic stress.
Project description:Proteins begin to fold as they emerge from translating ribosomes. The kinetics of ribosome transit along a given mRNA can influence nascent chain folding, but the extent to which individual codon translation rates impact proteome integrity remains unknown. Here, we show that slower decoding of discrete codons elicits widespread protein aggregation in vivo. Using ribosome profiling, we find that loss of anticodon wobble uridine (U34) modifications in a subset of tRNAs leads to ribosome pausing at their cognate codons in S. cerevisiae and C. elegans. Yeast cells lacking U34 modifications exhibit gene expression hallmarks of proteotoxic stress and accumulate aggregates of endogenous proteins with key cellular functions. Moreover, these cells are severely compromised in clearing stress-induced protein aggregates. Overexpression of hypomodified tRNAs alleviates ribosome pausing, concomitantly restoring protein homeostasis. Our findings demonstrate that modified U34 is an evolutionarily conserved accelerator of decoding and reveal an unanticipated role for tRNA anticodon modifications in maintaining proteome integrity. Ribosome profiling of wild-type and tRNA modification-deficient yeast and nematodes. Yeast samples were generated in various growth conditions (rich medium versus stress induced by treatment with diamide or rapamycin) and paired mRNA-Seq was performed on a subset of samples. Dataset contains three biological replicates for yeast samples and two biological replicates for nematode samples.