Rabaptin5 targets autophagy to damaged endosomes and Salmonella vacuoles via FIP200 and ATG16L1.
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ABSTRACT:
SUBMITTER: Millarte V
PROVIDER: S-EPMC8728625 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Autophagy is a finely orchestrated cellular catabolic process that requires multiple autophagy-related gene products (ATG proteins). The ULK1 complex functions to integrate upstream signals to downstream ATG proteins through an unknown mechanism. Here we have identified an interaction between mammalian FIP200 and ATG16L1, essential components of the ULK1 and ATG5 complexes, respectively. Further analyses show this is a direct interaction mediated by a short domain of ATG16L1 that we term the FIP200-binding domain (FBD). The FBD is not required for ATG16L1 self-dimerization or interaction with ATG5. Notably, an FBD-deleted ATG16L1 mutant is defective in mediating amino acid starvation-induced autophagy, which requires the ULK1 complex. However, this mutant retains its function in supporting glucose deprivation-induced autophagy, a ULK1 complex-independent process. This study therefore identifies a previously uncharacterized interaction between the ULK1 and ATG5 complexes that can distinguish ULK1-dependent and -independent autophagy processes.
| S-EPMC3565010 | biostudies-literature
Project description:The membrane source for autophagosome biogenesis is an unsolved mystery in the study of autophagy. ATG16L1 forms a complex with ATG12-ATG5 (the ATG16L1 complex). The ATG16L1 complex is recruited to autophagic membranes to convert MAP1LC3B-I to MAP1LC3B-II. The ATG16L1 complex dissociates from the phagophore before autophagosome membrane closure. Thus, ATG16L1 can be used as an early event marker for the study of autophagosome biogenesis. We found that among 3 proteins in the ATG16L1 complex, only ATG16L1 formed puncta-like structures when transiently overexpressed. ATG16L1+ puncta formed by transient expression could represent autophagic membrane structures. We thoroughly characterized the transiently expressed ATG16L1 in several mammalian cell lines. We found that transient expression of ATG16L1 not only inhibited autophagosome biogenesis, but also aberrantly targeted RAB11-positive recycling endosomes, resulting in recycling endosome aggregates. We conclude that transient expression of ATG16L1 is not a physiological model for the study of autophagy. Caution is warranted when reviewing findings derived from a transient expression model of ATG16L1.
| S-EPMC5724932 | biostudies-literature
Project description:Autophagosome formation is a dynamic process that is strictly controlled by autophagy-related (Atg) proteins. However, how these Atg proteins are recruited to the autophagosome formation site or autophagic membranes remains poorly understood. Here, we found that FIP200, which is involved in proximal events, directly interacts with Atg16L1, one of the downstream Atg factors, in an Atg14- and phosphatidylinositol 3-kinase-independent manner. Atg16L1 deletion mutants, which lack the FIP200-interacting domain, are defective in proper membrane targeting. Thus, FIP200 regulates not only early events but also late events of autophagosome formation through direct interaction with Atg16L1.
| S-EPMC3589088 | biostudies-other
Project description:Intestinal epithelial cells aid in mucosal defense by providing a physical barrier against entry of pathogenic bacteria and secreting antimicrobial peptides (AMPs). Autophagy is an important component of immune homeostasis. However, little is known about its role in specific cell types during bacterial infection in vivo. We investigated the role of autophagy in the response of intestinal epithelial and antigen-presenting cells to Salmonella infection in mice.We generated mice deficient in Atg16l1 in epithelial cells (Atg16l1(f/f) × Villin-cre) or CD11c(+) cells (Atg16l1(f/f) × CD11c-cre); these mice were used to assess cell type-specific antibacterial autophagy. All responses were compared with Atg16l1(f/f) mice (controls). Mice were infected with Salmonella enterica serovar typhimurium; cecum and small-intestine tissues were collected for immunofluorescence, histology, and quantitative reverse-transcription polymerase chain reaction analyses of cytokines and AMPs. Modulators of autophagy were screened to evaluate their effects on antibacterial responses in human epithelial cells.Autophagy was induced in small intestine and cecum after infection with S typhimurium, and required Atg16l1. S typhimurium colocalized with microtubule-associated protein 1 light chain 3? (Map1lc3b or LC3) in the intestinal epithelium of control mice but not in Atg16l1(f/f) × Villin-cre mice. Atg16l1(f/f) × Villin-cre mice also had fewer Paneth cells and abnormal granule morphology, leading to reduced expression of AMPs. Consistent with these defective immune responses, Atg16l1(f/f) × Villin-cre mice had increased inflammation and systemic translocation of bacteria compared with control mice. In contrast, we observed few differences between Atg16l1(f/f) × CD11c-cre and control mice. Trifluoperazine promoted autophagy and bacterial clearance in HeLa cells; these effects were reduced upon knockdown of ATG16L1.Atg16l1 regulates autophagy in intestinal epithelial cells and is required for bacterial clearance. It also is required to prevent systemic infection of mice with enteric bacteria.
| S-EPMC3840157 | biostudies-literature
Project description:Autophagy defends the mammalian cytosol against bacterial infection. Efficient pathogen engulfment is mediated by cargo-selecting autophagy adaptors that rely on unidentified pattern-recognition or danger receptors to label invading pathogens as autophagy cargo, typically by polyubiquitin coating. Here we show in human cells that galectin 8 (also known as LGALS8), a cytosolic lectin, is a danger receptor that restricts Salmonella proliferation. Galectin 8 monitors endosomal and lysosomal integrity and detects bacterial invasion by binding host glycans exposed on damaged Salmonella-containing vacuoles. By recruiting NDP52 (also known as CALCOCO2), galectin 8 activates antibacterial autophagy. Galectin-8-dependent recruitment of NDP52 to Salmonella-containing vesicles is transient and followed by ubiquitin-dependent NDP52 recruitment. Because galectin 8 also detects sterile damage to endosomes or lysosomes, as well as invasion by Listeria or Shigella, we suggest that galectin 8 serves as a versatile receptor for vesicle-damaging pathogens. Our results illustrate how cells deploy the danger receptor galectin 8 to combat infection by monitoring endosomal and lysosomal integrity on the basis of the specific lack of complex carbohydrates in the cytosol.
| S-EPMC3343631 | biostudies-literature
Project description:The cAMP-dependent protein kinase A (PKA) regulates a plethora of cellular functions in health and disease. During angiogenesis, PKA activity in endothelial cells controls the transition from sprouting to vessel maturation and limits tip cell formation independently of Notch signaling. The molecular PKA targets mediating these effects remain unknown. We report a chemical genetics screen identifying endothelial-specific substrates of PKA in human umbilical vein endothelial cells (HUVEC). We identified ATG16L1, a regulator of autophagy, as novel target of PKA. Biochemical validation, mass spectrometry and peptide spot arrays revealed that PKA phosphorylates ATG16L1α at Ser268 and ATG16L1β at Ser269. The phosphorylations drive degradation of ATG16L1 protein. Knocking down PKA or inhibiting its activity increased ATG16L1 protein levels and endothelial autophagy. In vivo genetics and pharmacological experiments demonstrated that autophagy inhibition partially rescues vascular hypersprouting caused by PKA deficiency. We propose that endothelial PKA activity restricts active sprouting by reducing endothelial autophagy through phosphorylation of ATG16L1.
2019-10-04 | PXD012975 | Pride
Project description:Deficiencies in DNA-degrading nucleases lead to accumulation of self DNA and induction of autoimmunity in mice and in monogenic and polygenic human diseases. However, the sources of DNA and the mechanisms that trigger immunity remain unclear. We analyzed mice deficient for the lysosomal nuclease Dnase2a and observed elevated levels of undegraded DNA in both phagocytic and nonphagocytic cells. In nonphagocytic cells, the excess DNA originated from damaged DNA in the nucleus based on colocalization studies, live-cell imaging, and exacerbation by DNA-damaging agents. Removal of damaged DNA by Dnase2a required nuclear export and autophagy-mediated delivery of the DNA to lysosomes. Finally, DNA was found to accumulate in Dnase2a(-/-) or autophagy-deficient cells and induce inflammation via the Sting cytosolic DNA-sensing pathway. Our results reveal a cell-autonomous process for removal of damaged nuclear DNA with implications for conditions with elevated DNA damage, such as inflammation, cancer, and chemotherapy.
| S-EPMC4555847 | biostudies-literature
Project description:Autophagy is a highly inducible system of intracellular degradation that occurs in lysosomes or vacuoles. Transmembrane 74 (TMEM74) has been shown to induce autophagy. However, the mechanism by which TMEM74 stimulates autophagy and the impacts of TMEM74-induced autophagy on tumor cell survival remain unclear. In this study, TMEM74 was shown to increase the autophagic flux process in different tumor cell lines. Further investigations revealed that TMEM74 interacts with ATG16L1 and ATG9A. Moreover, distinctive from the common autophagy models, it is found that TMEM74-related autophagy is independent of BECN1/PI3KC3 complex and ULK1, and TMEM74 may initiate and promote autophagy directly via interactions with ATG16L1 and ATG9A responsible for the nucleation and elongation respectively. Considering the ultimate outcome of TMEM74-induced autophagy in tumor cells, TMEM74-triggered autophagy induces a pro-survival effect on tumor cells, particularly cells under metabolic stress, consistent with alteration of a series of signal pathways. Intriguingly, TMEM74 itself can be downregulated through the autophagic process, which indicates that a potential self-regulatory loop exists so as to maintain an appropriate level of autophagy, avoiding excessive autophagy to commit tumor cells to death. According to the clinical database analysis, the high expression of TMEM74 significantly shortens the surviving periods of patients in several specific cancers indicating that TMEM74 itself can be treated as an effective potential target with clinical values to prolong surviving periods of cancer patients in the future. In conclusion, our study reveals a new mechanism by which autophagy is stimulated by a novel positive modulator through a unique pathway and demonstrates a novel connection between autophagy and cell survival, which undoubtedly serves to broaden our understanding of autophagy.
| S-EPMC5596558 | biostudies-literature
Project description:ObjectiveThis study aimed to uncover a critical protein and its mechanisms in modulating autophagy in Graves' disease (GD)-induced osteoporosis (OP).MethodsWe discovered the target protein, death-associated protein 1 (DAP1), using bone proteomics analysis. Furthermore, genetic overexpression and knockdown (KD) of DAP1 in bone and MC3T3-E1 cells revealed DAP1 effects on autophagy and osteogenic markers, and autophagic vacuoles in cells were detected using transmission electron microscopy and the microtubule-associated protein 1 light chain 3 alpha (MAP1LC3/LC3) dual fluorescence system. An autophagy polymerase chain reaction (PCR) array kit was used to identify the key molecules associated with DAP1-regulated autophagy.ResultsDAP1 levels were significantly higher in the bone tissue of GD mice and MC3T3-E1 cells treated with triiodothyronine (T3). DAP1 overexpression reduced LC3 lipidation, autophagic vacuoles, RUNX family transcription factor 2 (RUNX2), and osteocalcin (OCN) expression in MC3T3-E1 cells, whereas DAP1 KD reversed these changes. In vivo experiments revealed that GD mice with DAP1 KD had greater bone mass than control mice. DAP1-overexpressing (OE) cells had lower levels of phosphorylated autophagy-related 16-like 1 (ATG16L1) and LC3 lipidation, whereas DAP1-KD cells had higher levels.ConclusionsDAP1 was found to be a critical regulator of autophagy homeostasis in GD mouse bone tissue and T3-treated osteoblasts because it negatively regulated autophagy and osteogenesis in osteoblasts via the ATG16L1-LC3 axis.
| S-EPMC10512661 | biostudies-literature
Project description:Methylmercury causes serious damage to the central nervous system, but the molecular mechanisms of methylmercury toxicity are only marginally understood. In this study, we used a gene-deletion mutant library of budding yeast to conduct genome-wide screening for gene knockouts affecting the sensitivity of methylmercury toxicity. We successfully identified 31 genes whose deletions confer resistance to methylmercury in yeast, and 18 genes whose deletions confer hypersensitivity to methylmercury. Yeast genes whose deletions conferred resistance to methylmercury included many gene encoding factors involved in protein transport to vacuoles. Detailed examination of the relationship between the factors involved in this transport system and methylmercury toxicity revealed that mutants with loss of the factors involved in the transportation pathway from the trans-Golgi network (TGN) to the endosome, protein uptake into the endosome, and endosome-vacuole fusion showed higher methylmercury resistance than did wild-type yeast. The results of our genetic engineering study suggest that this vesicle transport system (proteins moving from the TGN to vacuole via endosome) is responsible for enhancing methylmercury toxicity due to the interrelationship between the pathways. There is a possibility that there may be proteins in the cell that enhance methylmercury toxicity through the protein transport system.
| S-EPMC4118254 | biostudies-other