Project description:Mitochondria are signaling hubs in eukaryotic cells. Here, we showed that the mitochondrial FUN14 domain-containing protein-1 (FUNDC1), an effector of Parkin-independent mitophagy, also participates in cellular plasticity by sustaining oxidative bioenergetics, buffering ROS production, and supporting cell proliferation. Targeting this pathway in cancer cells suppressed tumor growth but rendered transformed cells more motile and invasive in a manner dependent on ROS-mediated mitochondrial dynamics and mitochondrial repositioning to the cortical cytoskeleton. Global metabolomics and proteomics profiling identified a FUNDC1 interactome at the mitochondrial inner membrane, comprising the AAA+ protease, LonP1, and subunits of oxidative phosphorylation, complex V (ATP synthase). Independently of its previously identified role in mitophagy, FUNDC1 enabled LonP1 proteostasis, which in turn preserved complex V function and decreased ROS generation. Therefore, mitochondrial reprogramming by a FUNDC1-LonP1 axis controls tumor cell plasticity by switching between proliferative and invasive states in cancer.
Project description:Mitochondria-derived reactive oxygen species (mROS) are required for the survival, proliferation, and metastasis of cancer cells. The mechanism by which mitochondrial metabolism regulates mROS levels to support cancer cells is not fully understood. To address this, we conducted a metabolism-focused CRISPR/Cas9 genetic screen and uncovered that loss of genes encoding subunits of mitochondrial complex I were deleterious in the presence of the mitochondria-targeted antioxidant Mito-Vitamin E (MVE). Genetic or pharmacologic inhibition of mitochondrial complex I in combination with the mitochondria-targeted antioxidants, MVE or MitoTEMPO, induced a robust integrated stress response (ISR) and markedly diminished cell survival and proliferation in vitro. Notably, this was not observed following inhibition of mitochondrial complex III. Administration of MitoTEMPO in combination with the mitochondrial complex I inhibitor phenformin decreased the leukemic burden in a mouse model of T-cell acute lymphoblastic leukemia. Thus, mitochondrial complex I is a dominant metabolic determinant of mROS-dependent cellular fitness.
Project description:Hypoxia is a driver of aggressive tumor behavior, but the mechanisms are not completely understood. In a global phosphoproteomics screen, we now demonstrate that hypoxia induces the recruitment of Akt2 to tumor mitochondria, and Akt phosphorylation of pyruvate dehydrogenase kinase (PDK1) on Thr346. In turn, Akt-phosphorylated PDK1 shuts off oxidative phosphorylation via phosphorylation of the pyruvate dehydrogenase complex, and reprograms tumor metabolism towards glycolysis. Akt-phosphorylation of PDK1 is required to prevent autophagy, maintain cell viability and support tumor cell proliferation in hypoxia, in vivo. Therefore, mitochondrial Akt is a pathophysiologic switch for tumor adaptation in hypoxia.
Project description:Modulation of CD8 coreceptor levels can profoundly affect T-cell sensitivity to antigen. Here we show that the heritable downregulation of CD8 during type 2 polarization of murine CD8(+) effector T cells in vitro and in vivo is associated with CpG methylation of several regions of the Cd8a locus. These epigenetic modifications are maintained long-term in vivo following adoptive transfer. Even after extended type 2 polarization, however, some CD8(low) effector cells respond to interferon-? by re-expressing CD8 and a type 1 cytokine profile in association with partial Cd8a demethylation. Cd8a methylation signatures in naive, polarized and repolarized cells are distinct from those observed during the initiation, maintenance and silencing of CD8 expression by developing T cells in the thymus. This persistent capacity for epigenetic reprogramming of coreceptor levels on effector CD8(+) T cells enables the heritable tuning of antigen sensitivity in parallel with changes in type 1/type 2 cytokine balance.
Project description:Mitochondria are the energy-generating hubs of the cell. In spite of considerable advances, our understanding of the factors that regulate the molecular circuits that govern mitochondrial function remains incomplete. Using a genome-wide functional screen, we have identified the poorly characterized protein Zinc finger CCCH-type containing 10 (Zc3h10) as regulator of mitochondrial physiology. We show that Zc3h10 is a nuclear RNA binding protein that controls the fate of Slc25a37 and Prelid3a mRNA transcripts, two nuclear-encoded mitochondrial proteins central for iron and cardiolipin homeostasis. Depletion of Zc3h10 results in mitochondrial dysfunction and reduced TCA cycle flux. Notably, we have identified a loss-of-function mutation of Zc3h10 in humans (Tyr105 to Cys105) that is associated with decreased mitochondrial function, increased body mass index, fat mass, fasting glucose and triglycerides. Cells from Cys105 homozygotes display alterations in Slc25a37 and Prelid3a levels and defects in mitochondrial iron and cardiolipin homeostasis that derive in mitochondrial dysfunction.
Project description:Mitochondria were isolated from skeletal muscle and the remaining tissue fraction was collected to identify RNA enriched in mitochondria.
Project description:Mitochondria were isolated from heart tissue and the remaining tissue fraction was collected to identify RNA enriched in mitochondria.
Project description:Post-transcriptional mechanisms have the potential to influence complex changes in gene expression, yet their role in cell fate transitions remains largely unexplored. Here, we show that suppression of the RNA helicase DDX6 endows human and mouse primed embryonic stem cells (ESCs) with a differentiation-resistant, "hyper-pluripotent" state, which readily reprograms to a naive state resembling the preimplantation embryo. We further demonstrate that DDX6 plays a key role in adult progenitors where it controls the balance between self-renewal and differentiation in a context-dependent manner. Mechanistically, DDX6 mediates the translational suppression of target mRNAs in P-bodies. Upon loss of DDX6 activity, P-bodies dissolve and release mRNAs encoding fate-instructive transcription and chromatin factors that re-enter the ribosome pool. Increased translation of these targets impacts cell fate by rewiring the enhancer, heterochromatin, and DNA methylation landscapes of undifferentiated cell types. Collectively, our data establish a link between P-body homeostasis, chromatin organization, and stem cell potency.
Project description:Mitochondria are the energy-generating hubs of the cell. In spite of considerable advances, our understanding of the factors that regulate the molecular circuits that govern mitochondrial function remains incomplete. Using a genome-wide functional screen, we have identified the poorly characterized protein Zinc finger CCCH-type containing 10 (Zc3h10) as regulator of mitochondrial physiology. We show that Zc3h10 is a nuclear RNA binding protein that controls the fate of Slc25a37 and Prelid3a mRNA transcripts, two nuclear-encoded mitochondrial proteins central for iron and cardiolipin homeostasis. Depletion of Zc3h10 results in mitochondrial dysfunction and reduced TCA cycle flux. Notably, we have identified a loss-of-function mutation of Zc3h10 in humans (Tyr105 to Cys105) that is associated with decreased mitochondrial function, increased body mass index, fat mass, fasting glucose and triglycerides. Cells from Cys105 homozygotes display alterations in Slc25a37 and Prelid3a levels and defects in mitochondrial iron and cardiolipin homeostasis that derive in mitochondrial dysfunction.