Abstract
ULK1 and ULK2 are thought to be essential for initiating autophagy, and Ulk1/2-deficient mice die perinatally of autophagy-related defects. Therefore, we used a conditional knockout approach to investigate the roles of ULK1/2 in the brain. Although the mice showed neuronal degeneration, the neurons showed no accumulation of P62(+)/ubiquitin(+) inclusions or abnormal membranous structures, which are observed in mice lacking other autophagy genes. Rather, neuronal death was associated with activation of the unfolded protein response (UPR) pathway. An unbiased proteomics approach identified SEC16A as an ULK1/2 interaction partner. ULK-mediated phosphorylation of SEC16A regulated the assembly of endoplasmic reticulum (ER) exit sites and ER-to-Golgi trafficking of specific cargo, and did not require other autophagy proteins (e.g., ATG13). The defect in ER-to-Golgi trafficking activated the UPR pathway in ULK-deficient cells; both processes were reversed upon expression of SEC16A with a phosphomimetic substitution. Thus, the regulation of ER-to-Golgi trafficking by ULK1/2 is essential for cellular homeostasis.
Copyright © 2016 Elsevier Inc. All rights reserved.
MeSH terms
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Animals
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Autophagy
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Autophagy-Related Protein 7 / genetics
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Autophagy-Related Protein 7 / metabolism
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Autophagy-Related Protein-1 Homolog / deficiency
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Autophagy-Related Protein-1 Homolog / genetics
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Autophagy-Related Protein-1 Homolog / metabolism*
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Brain / enzymology*
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Brain / pathology
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COP-Coated Vesicles / enzymology
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Caenorhabditis elegans / enzymology
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Caenorhabditis elegans / genetics
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Caenorhabditis elegans Proteins / metabolism
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Endoplasmic Reticulum / enzymology*
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Endoplasmic Reticulum / pathology
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Female
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Fibroblasts / enzymology*
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Genotype
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Golgi Apparatus / enzymology*
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Golgi Apparatus / pathology
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HEK293 Cells
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Homeostasis
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Humans
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Male
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Mice, 129 Strain
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Mice, Inbred C57BL
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Mice, Knockout
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Nerve Degeneration
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Phenotype
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Phosphorylation
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Protein Serine-Threonine Kinases / deficiency
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Protein Transport
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RNA Interference
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Time Factors
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Transfection
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Unfolded Protein Response
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Vesicular Transport Proteins / genetics
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Vesicular Transport Proteins / metabolism
Substances
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Atg7 protein, mouse
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Caenorhabditis elegans Proteins
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Carrier Proteins
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Nuclear Proteins
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Sec13 protein, mouse
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Sec16a protein, mouse
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Sec23a protein, mouse
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Vesicular Transport Proteins
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sec-23 protein, C elegans
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Ulk2 protein, mouse
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Autophagy-Related Protein-1 Homolog
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Protein Serine-Threonine Kinases
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Ulk1 protein, mouse
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Autophagy-Related Protein 7