Abstract
Macroautophagy is a physiological cellular response to nutrient stress, which leads to the engulfment of cytosolic contents by a double-walled membrane structure, the phagophore. Phagophores seal to become autophagosomes, which then fuse with lysosomes to deliver their contents for degradation. Macroautophagy is regulated by numerous cellular factors, including the Class III PI3K (phosphoinositide 3-kinase) Vps34 (vacuolar protein sorting 34). The autophagic functions of Vps34 require its recruitment to a complex that includes Vps15, Beclin-1 and Atg14L (autophagy-related 14-like protein) and is known as Vps34 Complex I. We have now identified NRBF2 (nuclear receptor-binding factor 2) as a new member of Vps34 Complex I. NRBF2 binds to complexes that include Vps34, Vps15, Beclin-1 and ATG-14L, but not the Vps34 Complex II component UVRAG (UV radiation resistance-associated gene). NRBF2 directly interacts with Vps15 via the Vps15 WD40 domain as well as other regions of Vps15. The formation of GFP-LC3 (light chain 3) punctae and PE (phosphatidylethanolamine)-conjugated LC3 (LC3-II) in serum-starved cells was inhibited by NRBF2 knockdown in the absence and presence of lysosomal inhibitors, and p62 levels were increased. Thus NRBF2 plays a critical role in the induction of starvation-induced autophagy as a specific member of Vps34 Complex I.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adaptor Proteins, Vesicular Transport / genetics
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Adaptor Proteins, Vesicular Transport / metabolism
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Apoptosis Regulatory Proteins / genetics
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Apoptosis Regulatory Proteins / metabolism
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Autophagy / genetics*
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Autophagy-Related Proteins
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Beclin-1
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Class III Phosphatidylinositol 3-Kinases / genetics*
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Class III Phosphatidylinositol 3-Kinases / metabolism
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Gene Expression Regulation
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Genes, Reporter
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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HEK293 Cells
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism
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Humans
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Lysosomes / metabolism
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Microtubule-Associated Proteins / genetics
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Microtubule-Associated Proteins / metabolism
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Mitochondrial Proteins / genetics
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Mitochondrial Proteins / metabolism
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Phagosomes / metabolism
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Protein Transport
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Signal Transduction
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Trans-Activators / antagonists & inhibitors
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Trans-Activators / genetics*
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Trans-Activators / metabolism
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Tumor Suppressor Proteins / genetics
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Tumor Suppressor Proteins / metabolism
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Vacuolar Sorting Protein VPS15 / genetics
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Vacuolar Sorting Protein VPS15 / metabolism
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Vacuoles / metabolism
Substances
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ATG14 protein, human
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Adaptor Proteins, Vesicular Transport
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Apoptosis Regulatory Proteins
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Autophagy-Related Proteins
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BECN1 protein, human
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Beclin-1
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HSP70 Heat-Shock Proteins
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HSPA9 protein, human
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MAP1LC3A protein, human
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Membrane Proteins
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Microtubule-Associated Proteins
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Mitochondrial Proteins
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NRBF2 protein, human
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RNA, Small Interfering
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Trans-Activators
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Tumor Suppressor Proteins
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UVRAG protein, human
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Green Fluorescent Proteins
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Class III Phosphatidylinositol 3-Kinases
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PIK3R4 protein, human
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Vacuolar Sorting Protein VPS15