Mytho, An Uncharacterized Gene that Controls Longevity and WIPI2-dependent Autophagy
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ABSTRACT: The identification of genes that confer either extension of life span or accelerate age-related decline was a step forward in our understanding the mechanisms of senescence and revealed that aging process is partially controlled by genetics and transcriptional programs. Here we identified that the unknown DNA sequence c16orf70 encodes for a protein, named Mytho, that controls life span. Mytho is conserved from worms to humans and is upregulated in aged mice and elderly people. Deletion of the ortholog Mytho gene in C. elegans dramatically shortened life-span and decreased animal survival upon exposure to oxidative stress. Mechanistically, MYTHO is required for autophagy because it acts as scaffold to recruit and assemble the conjugation system at the phagophore assembly site (PAS). We conclude that Mytho is a transcriptionally regulated initiator of autophagy that is central in promoting stress resistance to ensure organism longevity.
Project description:Birt-Hogg-Dubè (BHD) syndrome is an inherited condition caused by loss-of-function mutations in the gene encoding the tumor-suppressor protein folliculin (FLCN) and frequently associated with kidney cysts and cancer. FLCN acts as a negative regulator of TFEB and TFE3 transcription factors, master controllers of lysosomal biogenesis and autophagy, by enabling their phosphorylation by the mechanistic Target Of Rapamycin Complex 1 (mTORC1). We previously showed that deletion of TFEB rescued the renal cystic phenotype of kidney-specific Flcn KO mice. Using Flcn/TFEB/TFE3 double and triple KO mice we now show that both TFEB and TFE3 contribute, in a differential and cooperative manner, to kidney cystogenesis. Importantly, silencing of either TFEB or TFE3 rescued tumorigenesis in patient-derived xenografts (PDXs) generated from a kidney tumor of a BHD patient. Furthermore, transcriptome analyses performed in transgenic mice, PDXs and patient tumor samples revealed TFEB/TFE3 downstream targets that may contribute to their tumorigenic activity. Our findings demonstrate in disease-relevant models that TFEB and TFE3 are key drivers of kidney tumorigenesis and suggest novel therapeutic strategies based on the inhibition of these transcription factors.
Project description:Degradation of the endoplasmic reticulum (ER) by selective autophagy (ER-phagy) is vital for cellular homeostasis. Here, we introduce FAM134A/RETREG2 and FAM134C/RETREG3 as new ER-phagy receptors. FAM134A and FAM134C exist in a relatively inactive state under basal conditions and require an activation signal to induce significant ER fragmentation. Molecular modeling and simulations implicate a single compact fold of FAM134A’s reticulon homology domain (RHD). In contrast, the RHDs of FAM134B and FAM134C are able to adopt at least three discrete conformations. These differences result in slower vesicle formation for FAM134A compared to FAM134C and mostly FAM134B. Global proteomic analyses of knockout MEFs indicate both distinct and overlapping roles for the Fam134s, with Fam134a being most distant from Fam134b and Fam134c. Fam134c appears to enhance and facilitate Fam134b’s role in maintaining pro-collagen-I levels and is therefore insufficient to compensate for its loss. By contrast, Fam134a has a particular mode of action in maintaining pro-collagen-I levels and is able to fully compensate loss of Fam134b or Fam134c upon over-expression in its wild-type or LIR mutant form.
Project description:The degradation of endoplasmic reticulum (ER) via selective autophagy is driven by the ER-phagy receptors that facilitate the incorporation of ER-fragments into nascent autophagosomes. How these receptors are regulated, in response to ER-phagy-inducing stimuluses, is largely unknown. Here we propose that starvation, as well as mTOR inhibition, triggers ER-phagy primarily through the activation of the ER-phagy receptor FAM134C. In physiological, nutrient reach, conditions FAM134C is phosphorylated by the Casein kinase 2 (CK2) protein at specific residues negatively affecting FAM134C interaction with the LC3 proteins, thereby preventing ER-phagy. Pharmacological or starvation-induced mTORC1 inhibition limits phosphorylation of FAM134C by CK2, hence promoting FAM134C activation and ER-phagy. Moreover, inhibition of CK2 or the expression of a phospho-mutant FAM134C protein is sufficient to stimulate ER-phagy. Conversely, starvation induced ER-phagy is inhibited in cells and mice that lack FAM134C or expressing a phospho-mimetic FAM134C protein. Overall, these data describe a new mechanism regulating ER-phagy and provides an example of cargo selectivity mechanism during starvation induced autophagy.
Project description:Angiogenesis, the formation of new blood vessels from pre-existing ones, is a complex and demanding biological process that plays an important role in physiological as well as pathological settings such as cancer and ischemia. Given its critical role, the regulation of endothelial growth factor receptor (e.g. VEGFR2, FGFR1) represents important mechanisms for the control of angiogenesis. Recent evidences support cell metabolism as a critical regulator of angiogenesis. However, it is unknown how glutamine metabolism regulates growth factor receptor expression. Here, by using genetic and pharmacological approaches, we show that glutaminolysis and glutamate-dependent transaminases (TAs) support alpha-ketoglutarate (αKG) levels and are critical regulators of angiogenic response during pathological conditions. Indeed, the endothelial specific blockage of GLS1 impairs ischemic and tumor angiogenesis by suppressing VEGFR2 translation via mTORC1-dependent pathway. Lastly, we discover that ECs catabolized the glutamine-derived glutamate via phosphoserine aminotransferase 1 (PSAT1) as crucial to support VEGFR2 translation. These findings identify glutamine anaplerosis and TA activity as a critical regulator of growth factor receptor translation in normal and pathological angiogenesis. We anticipate our studies to be a starting point for novel anti-angiogenesis approaches based on GLS1/PSAT1 inhibitor treatments to overcome anti-VEGF therapies resistance.
Project description:Several RNA-binding proteins (RBPs) are implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), including the FET proteins FUS, TAF15 and EWSR1. Cabeza (caz) is the single Drosophila FET ortholog. Here, we identified Xrp1, a poorly characterized DNA-binding protein, as a key modifier of caz mutant phenotypes. Xrp1 expression was strongly upregulated in caz mutants, and Xrp1 heterozygosity rescued their motor defects and life span. Interestingly, selective neuronal Xrp1 knock-down was sufficient to rescue, and neuronal Xrp1 overexpression phenocopied caz mutant phenotypes. The caz/Xrp1 genetic interaction depended on the functionality of the AT-hook DNA-binding domain in Xrp1. Consistently, caz mutants displayed gene expression dysregulation, which was mitigated by Xrp1 heterozygosity. Finally, Xrp1 knock-down substantially rescued the motor deficits and life span of flies expressing ALS-mutant FUS in motor neurons. Taken together, caz mutant phenotypes are mediated by increased neuronal Xrp1 levels, leading to gene expression dysregulation and neuronal dysfunction.
Project description:Small ubiquitin-like modifiers from the ATG8 family regulate autophagy initiation and progression in mammalian cells. Their interaction with LC3-interacting region (LIR) containing proteins promotes cargo sequestration, phagophore assembly, or even fusion between autophagosomes and lysosomes. Previously, we have shown that RabGAP proteins from the TBC family directly bind to LC3/GABARAP proteins. In the present study, we focus on the function of TBC1D2B. We show that TBC1D2B contains a functional canonical LIR motif and acts at an early stage of autophagy by binding to both LC3/GABARAP proteins and ATG5 conjugation machinery. Subsequently, TBC1D2B is degraded by autophagy. TBC1D2B condensates into liquid droplets upon autophagy induction. Our study suggests that phase separation is an underlying mechanism of TBC1D2B-dependent autophagy induction, which serves as an assembly platform for further cargo sequestration.
Project description:Naive pluripotent epiblast cells of the preimplantation murine embryo and their in vitro counterpart, embryonic stem (ES) cells, have the capacity to give rise to all cells of the adult. Such developmental plasticity is associated with global genome hypomethylation. It is unclear whether genome methylation is dynamically regulated only via differential expression of DNA methyltransferases (DNMTs) and Ten-eleven Translocation (TET) enzymes, which oxidase methylated DNA. Here we show that LIF/Stat3 signalling induces genomic hypomethylation via metabolic reconfiguration. In Stat3-/- ES cells we observed decreased alpha-ketoglutarate (ɑKG) production from reductive Glutamine metabolism, leading to decreased TET activity, increased Dnmt3a/b expression and to a global increase in DNA methylation. Notably, genome methylation is dynamically controlled by simply modulating αKG availability, mitochondrial activity or Stat3 activation in mitochondria, indicating effective crosstalk between metabolism and the epigenome. Stat3-/- ES cells also show increased methylation at Imprinting Control Regions accompanied with differential expression of >50% of imprinted genes. Single-cell transcriptome analysis of Stat3-/- embryos confirmed dysregulated expression of Dnmt3a/b, Tet2, and imprinted genes in vivo. Our results reveal that the LIF/Stat3 signal bridges the metabolic and epigenetic profiles of naive pluripotent cells, ultimately controlling genome methylation and imprinted gene expression. Several imprinted genes regulate cell proliferation and are often misregulated in tumors. Moreover, a wide range of cancers display Stat3-overactivation, raising the possibility that the molecular module we described here is exploited under pathological conditions.
Project description:Structural cardiac lesions are often surgically repaired using prosthetic patches, which can be of biological or synthetic nature. In the current clinical scenario, amongst biological patches, are gaining very much interest those derived from decellularization of xenogeneic scaffold. These patches maintain their natural architecture of the extracellular matrix (ECM) after the removal of their native cells. Moreover, once implanted in the host, they promote tissue regeneration and repair, encourage angiogenesis, migration, proliferation, and host’s cell differentiation mechanisms. Finally, in the host, decellularized xenogeneic patches, after cells repopulation, reduce immuno-mediated response against the graft thus preventing device failure. Small intestinal submucosa (SIS) from porcine showed such properties in alternative clinical scenarios. The US FDA approved its use in humans for urogenital procedures, such as hernia repair, cystoplasties, ureteral reconstructions, stress incontinence, Peyronie’s disease, penile chordee, and urethral reconstruction for hypospadias and strictures. In addition, it has also been successfully used for the skeletal muscle tissue reconstruction in young patients. However, for cardiovascular applications, the results are still controversial. In this study, we aimed to validate our decellularization protocols for SIS, which is based on the use of Tergitol 15 S 9, by comparing it to our previous and efficient method (Triton X 100) which is not more available on the market. For both treatments, we evaluated the preservation of the ECM ultrastructure, mechanics, biocompatibility and final bioinductive capabilities. The overall analysis shows that the SIS tissue is macroscopically distinguishable into two regions, smooth or wrinkle, which are equivalent for ultrastructure and biochemical profile. Furthermore, Tergitol 15 S 9 treatment do not modify the mechanics of the tissue, resulting comparable to the native one and confirming the superior preservation of the collagen fibers. In summary, our study showed that the SIS decellularized with Tergitol 15 S 9 guarantees higher performance compared to Triton X 100 in all the fields of characterization explored and for all the components of the SIS: wrinkled and smooth.
Project description:The significant increase in the human life-span during the last century confronts us with great medical challenges. To answer them, one must understand and control the mechanisms that determine healthy ageing. The highly conserved sirtuin deacetylases were shown to regulate life-span in lower organisms. Yet, the role of mammalian sirtuins, SIRT1 to 7, in regulating life-span is currently unclear. Here, we show that in SIRT6 transgenic mice (Sirt6-tg), the males but not the females, have a significant increase in life-span. Gene expression analysis revealed significant differences for male Sirt6-tg in comparison to male wild-type mice. Transgenic males display lower serum IGF-1 levels, increased levels of IGFBP-1 and altered phosphorylation levels of major components of the IGF-1 pathway, a key factor in the regulation of life-span. This study is the first to show regulation of mammalian life-span by a sirtuin family member, and has important therapeutic implications for age-related diseases.
Project description:Comparison of wild type and heterozygote and homozygote chico mutants ( Clancy, et al. Extension of Life-Span by Loss of CHICO, a Drosophila Insulin Receptor Substrate Protein. Science 292 (5514), 104.) on Affymetrix Drosophila2 GeneChip. The flies (Drosophila melanogaster) are 7 day old adult females.