Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes

Andrew R.J. Young, Edmond Y W Chan, Xiao Wen Hu, Robert Köchl, Samuel G Crawshaw, Stephen High, Dale W Hailey, Jennifer Lippincott-Schwartz, Sharon A. Tooze

Research output: Contribution to journalArticle

465 Citations (Scopus)

Abstract

Autophagy, fundamentally a lysosomal degradation pathway, functions in cells during normal growth and certain pathological conditions, including starvation, to maintain homeostasis. Autophagosomes are formed through a mechanism that is not well understood, despite the identification of many genes required for autophagy. We have studied the mammalian homologue of Atg9p, a multi-spanning transmembrane protein essential in yeast for autophagy, to gain a better understanding of the function of this ubiquitious protein. We show that both the N- and C-termini of mammalian Atg9 (mAtg9) are cytosolic, and predict that mAtg9 spans the membrane six times. We find that mAtg9 is located in the trans-Golgi network and late endosomes and colocalizes with TGN46, the cation-independent mannose-6-phosphate receptor, Rab7 and Rab9. Amino acid starvation or rapamycin treatment, which upregulates autophagy, causes a redistribution of mAtg9 from the TGN to peripheral, endosomal membranes, which are positive for the autophagosomal marker GFP-LC3. siRNA-mediated depletion of the putative mammalian homologue of Atg1p, ULK1, inhibits this starvation-induced redistribution. The redistribution of mAtg9 also requires PI 3-kinase activity, and is reversed after restoration of amino acids. We speculate that starvation-induced autophagy, which requires mAtg9, may rely on an alteration of the steady-state trafficking of mAtg9, in a Atg1-dependent manner.

LanguageEnglish
Pages3888-3900
Number of pages13
JournalJournal of Cell Science
Volume119
Issue number18
DOIs
Publication statusPublished - 15 Sep 2006

Fingerprint

Endosomes
Autophagy
Starvation
IGF Type 2 Receptor
trans-Golgi Network
Amino Acids
Membranes
Sirolimus
Phosphatidylinositol 3-Kinases
Small Interfering RNA
Cations
Proteins
Homeostasis
Up-Regulation
Yeasts
Growth
Genes

Keywords

  • animals
  • endosomes
  • green fluorescent proteins
  • humans
  • intracellular signaling peptides and proteins
  • membrane proteins
  • protein transport
  • protein-serine-threonine kinases
  • rats
  • recombinant fusion proteins
  • rab GTP-binding proteins
  • trans-Golgi Network

Cite this

Young, A. R. J., Chan, E. Y. W., Hu, X. W., Köchl, R., Crawshaw, S. G., High, S., ... Tooze, S. A. (2006). Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. Journal of Cell Science, 119(18), 3888-3900. https://doi.org/10.1242/jcs.03172
Young, Andrew R.J. ; Chan, Edmond Y W ; Hu, Xiao Wen ; Köchl, Robert ; Crawshaw, Samuel G ; High, Stephen ; Hailey, Dale W ; Lippincott-Schwartz, Jennifer ; Tooze, Sharon A. / Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. In: Journal of Cell Science. 2006 ; Vol. 119, No. 18. pp. 3888-3900.
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Young, ARJ, Chan, EYW, Hu, XW, Köchl, R, Crawshaw, SG, High, S, Hailey, DW, Lippincott-Schwartz, J & Tooze, SA 2006, 'Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes' Journal of Cell Science, vol. 119, no. 18, pp. 3888-3900. https://doi.org/10.1242/jcs.03172

Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. / Young, Andrew R.J.; Chan, Edmond Y W; Hu, Xiao Wen; Köchl, Robert; Crawshaw, Samuel G; High, Stephen; Hailey, Dale W; Lippincott-Schwartz, Jennifer; Tooze, Sharon A.

In: Journal of Cell Science, Vol. 119, No. 18, 15.09.2006, p. 3888-3900.

Research output: Contribution to journalArticle

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T1 - Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes

AU - Young, Andrew R.J.

AU - Chan, Edmond Y W

AU - Hu, Xiao Wen

AU - Köchl, Robert

AU - Crawshaw, Samuel G

AU - High, Stephen

AU - Hailey, Dale W

AU - Lippincott-Schwartz, Jennifer

AU - Tooze, Sharon A.

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Y1 - 2006/9/15

N2 - Autophagy, fundamentally a lysosomal degradation pathway, functions in cells during normal growth and certain pathological conditions, including starvation, to maintain homeostasis. Autophagosomes are formed through a mechanism that is not well understood, despite the identification of many genes required for autophagy. We have studied the mammalian homologue of Atg9p, a multi-spanning transmembrane protein essential in yeast for autophagy, to gain a better understanding of the function of this ubiquitious protein. We show that both the N- and C-termini of mammalian Atg9 (mAtg9) are cytosolic, and predict that mAtg9 spans the membrane six times. We find that mAtg9 is located in the trans-Golgi network and late endosomes and colocalizes with TGN46, the cation-independent mannose-6-phosphate receptor, Rab7 and Rab9. Amino acid starvation or rapamycin treatment, which upregulates autophagy, causes a redistribution of mAtg9 from the TGN to peripheral, endosomal membranes, which are positive for the autophagosomal marker GFP-LC3. siRNA-mediated depletion of the putative mammalian homologue of Atg1p, ULK1, inhibits this starvation-induced redistribution. The redistribution of mAtg9 also requires PI 3-kinase activity, and is reversed after restoration of amino acids. We speculate that starvation-induced autophagy, which requires mAtg9, may rely on an alteration of the steady-state trafficking of mAtg9, in a Atg1-dependent manner.

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KW - animals

KW - endosomes

KW - green fluorescent proteins

KW - humans

KW - intracellular signaling peptides and proteins

KW - membrane proteins

KW - protein transport

KW - protein-serine-threonine kinases

KW - rats

KW - recombinant fusion proteins

KW - rab GTP-binding proteins

KW - trans-Golgi Network

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DO - 10.1242/jcs.03172

M3 - Article

VL - 119

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EP - 3900

JO - Journal of Cell Science

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SN - 0021-9533

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Young ARJ, Chan EYW, Hu XW, Köchl R, Crawshaw SG, High S et al. Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. Journal of Cell Science. 2006 Sep 15;119(18):3888-3900. https://doi.org/10.1242/jcs.03172