Sun, Q. et al. Identification of Barkor as a mammalian autophagy-specific factor for Beclin 1 and class III phosphatidylinositol 3-kinase. Proc. Natl. Acad. Sci. USA 105, 19211-19216

Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2009; 105(49):19211-6. DOI: 10.1073/pnas.0810452105
Source: PubMed

ABSTRACT

Autophagy mediates the cellular response to nutrient deprivation, protein aggregation, and pathogen invasion in human. Dysfunction of autophagy has been implicated in multiple human diseases including cancer. The identification of novel autophagy factors in mammalian cells will provide critical mechanistic insights into how this complicated cellular pathway responds to a broad range of challenges. Here, we report the cloning of an autophagy-specific protein that we called Barkor (Beclin 1-associated autophagy-related key regulator) through direct interaction with Beclin 1 in the human phosphatidylinositol 3-kinase class III complex. Barkor shares 18% sequence identity and 32% sequence similarity with yeast Atg14. Elimination of Barkor expression by RNA interference compromises starvation- and rapamycin-induced LC3 lipidation and autophagosome formation. Overexpression of Barkor leads to autophagy activation and increased number and enlarged volume of autophagosomes. Tellingly, Barkor is also required for suppression of the autophagy-mediated intracellular survival of Salmonella typhimurium in mammalian cells. Mechanistically, Barkor competes with UV radiation resistance associated gene product (UVRAG) for interaction with Beclin 1, and the complex formation of Barkor and Beclin1 is required for their localizations to autophagosomes. Therefore, we define a regulatory signaling pathway mediated by Barkor that positively controls autophagy through Beclin 1 and represents a potential target for drug development in the treatment of human diseases implicated in autophagic dysfunction.

Download full-text

Full-text

Available from: Weiliang Fan, Dec 22, 2014
    • "Incidentally, two Beclin1 negative regulators Bcl-2 and Rubicon bind respectively to the regions spanning Beclin 1's BH3 domain and Beclin 1's CCD and ECD domains, whereas ATG14L, a factor enabling Beclin 1 to activate the initiation complex (Kim et al., 2013), binds to the CCD domain of Beclin 1 (Sun et al., 2008). This domain occupancy on Beclin 1 is compatible with simultaneous binding of IRGM and ATG14L and exclusion of autophagy negative regulators. "
    [Show abstract] [Hide abstract]
    ABSTRACT: IRGM, encoded by a uniquely human gene conferring risk for inflammatory diseases, affects autophagy through an unknown mechanism. Here, we show how IRGM controls autophagy. IRGM interacts with ULK1 and Beclin 1 and promotes their co-assembly thus governing the formation of autophagy initiation complexes. We further show that IRGM interacts with pattern recognition receptors including NOD2. IRGM, NOD2, and ATG16L1, all of which are Crohn's disease risk factors, form a molecular complex to modulate autophagic responses to microbial products. NOD2 enhances K63-linked polyubiquitination of IRGM, which is required for interactions of IRGM with the core autophagy factors and for microbial clearance. Thus, IRGM plays a direct role in organizing the core autophagy machinery to endow it with antimicrobial and anti-inflammatory functions. Copyright © 2015 Elsevier Inc. All rights reserved.
    No preview · Article · Jan 2016 · Molecular Cell
  • Source
    • "; impaired bacteria clearance, unaffected obatoclax-induced toxicity, augmented genomic instability, aberrant cell apoptosis, and altered cell cycle, and cytoskeletal protein filamentous actin network in mouse embryonic fibroblasts Komatsu et al., 2005; Sun et al., 2008; McCoy et al., 2010; Lee et al., 2012; Zhuo et al., 2013 iUbc-Cre Perturbed glucose metabolism and inhibited progression of non-small cell lung cancer Karsli-Uzunbas et al., 2014 Liver Mx1-Cre Hepatomegaly with malformations of organelles and ubiquitin-positive protein aggregates Komatsu et al., 2005; Matsumoto et al., 2008 Alb-Cre Oxidative stress with increased total protein mass; excessive storage of triglyceride in lipid droplets during nutrient deprivation Matsumoto et al., 2008; Singh et al., 2009a GFAP-Cre Inhibited lipid release and fibrogenesis in hepatic stellate cells Hernandez-Gea et al., 2012 Pancreas RIP-Cre Impaired glucose tolerance; degenerated islets; decreased mitochondrial oxidation consumption and increased compensatory basal glycolytic rates and reactive oxygen species levels Ebato et al., 2008; Jung et al., 2008; Wu et al., 2009 Skeletal muscle MCK-Cre Decreased mitochondrial oxidation consumption and increased compensatory basal glycolytic rates and reactive oxygen species levels Wu et al., 2009 Endothelium VE-cadherin- Cre Impaired von Willebrand factor (VWF) release; susceptibility to bleomycin-induced pulmonary fibrosis Torisu et al., 2013; Singh et al., 2015 Vascular smooth muscle "
    [Show abstract] [Hide abstract]
    ABSTRACT: Macroautophagy is an evolutionarily conserved intracellular degradation system used by life ranging from yeasts to mammals. The core autophagic machinery is composed of ATG (autophagy-related) protein constituents. One particular member of the ATG protein family, Atg7, has been the focus of recent research. Atg7 acts as an E1-like activating enzyme facilitating both microtubule-associated protein light chain 3 (LC3)-phosphatidylethanolamine and ATG12 conjugation. Thus, Atg7 stands at the hub of these two ubiquitin-like systems involving LC3 and Atg12 in autophagic vesicle expansion. In this review, I focus on the pleiotropic function of Atg7 in development, maintenance of health, and alternations of such control in disease.
    Full-text · Article · Sep 2015 · Protein & Cell
  • Source
    • "Incidentally, two Beclin1 negative regulators Bcl-2 and Rubicon bind respectively to the regions spanning Beclin 1's BH3 domain and Beclin 1's CCD and ECD domains, whereas ATG14L, a factor enabling Beclin 1 to activate the initiation complex (Kim et al., 2013), binds to the CCD domain of Beclin 1 (Sun et al., 2008). This domain occupancy on Beclin 1 is compatible with simultaneous binding of IRGM and ATG14L and exclusion of autophagy negative regulators. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Polymorphisms in the IRGM gene, associated with Crohn disease (CD) and tuberculosis, are among the earliest identified examples documenting the role of autophagy in human disease. Functional studies have shown that IRGM protects against these diseases by modulating autophagy, yet the exact molecular mechanism of IRGM's activity has remained unknown. We have recently elucidated IRGM's mechanism of action. IRGM functions as a platform for assembling, stabilizing, and activating the core autophagic machinery, while at the same time physically coupling it to conventional innate immunity receptors. Exposure to microbial products or bacterial invasion increases IRGM expression, which leads to stabilization of AMPK. Specific protein-protein interactions and post-translational modifications such as ubiquitination of IRGM, lead to a co-assembly with IRGM of the key autophagy regulators ULK1 and BECN1 in their activated forms. IRGM physically interacts with two other CD risk factors, ATG16L1 and NOD2, placing these three principal players in CD within the same molecular complex. This explains how polymorphisms altering expression or function of any of the three factors individually can affect the same process - autophagy. Furthermore, IRGM's interaction with NOD2, and additional pattern recognition receptors such as NOD1, RIG-I and select TLRs, transduces microbial signals to the core autophagy apparatus. This work solves the long-standing enigma of how IRGM controls autophagy.
    Full-text · Article · Aug 2015 · Autophagy
Show more