Endoplasmic reticulum stress induced by 2-deoxyglucose but not glucose starvation activates AMPK through CaMKKβ leading to autophagy

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40 Scopus citations

Abstract

Autophagy, a well-conserved cellular self-eating process, has been shown to play a critical role in the pathophysiology of cancer. Previously, we reported that under normal O2 conditions (21% O2), the dual glucose metabolism inhibitor 2-deoxyglucose (2-DG) activates a cytoprotective autophagic response in cancer cells mainly through the induction of endoplasmic reticulum (ER) stress rather than ATP2 reduction. However, the pathway(s) by which this occurs was unknown. Here, we find that ER stress induced by 2-DG as well as tunicamycin activates AMPK via Ca2+- CaMKKβ leading to stimulation of autophagy. These results suggest a new role for AMPK as a sensor of ER stress. In contrast, we find that although physiologic glucose starvation (GS) leads to ER stress which contributes to autophagy activation, it does so by a different mechanism. In addition to ER stress, GS also stimulates autophagy through lowering ATP and activating the canonical LKB1-AMPK energy sensing pathway as well as through increasing reactive oxygen species resulting in the activation of ERK. Furthermore, under hypoxia we observe that both 2-DG and GS inhibit rather than activate autophagy. This inhibition correlates with dramatically depleted ATP levels, and occurs through reduction of the PI3K III-Beclin1 complex for autophagy initiation, blockage of the conjugation of ATG12 to ATG5 for autophagosome expansion, as well as inhibition of the functional lysosomal compartment for autophagic degradation. Taken together, our data support a model where under normoxia therapeutic (2-DG) and physiologic (GS) glucose restriction differentially activate autophagy, while under hypoxia they similarly inhibit it. Abbreviations2-DG2-deoxyglucose4-PBAsodium 4-phenylbutyrateACCacetyl-CoA carboxylaseAMPKAMP-activated protein kinaseATF6activating transcription factor 6ATGautophagy-related geneATPadenosine triphosphateBAPTABAPTA-AMBeclin1coiled- coil, moesin-like BCL2 interacting protein[Ca2+] ccytoplasmic Ca2+ concentration[Ca2+] ERER Ca2+ concentrationCaMKKβCa2+/ calmodulin-dependent kinase kinase βEGFPenhanced green fluorescent proteinERendoplasmic reticulumERKextracellular signal-regulated protein kinaseEST/Pep AEST and pepstatin AGrp78glucose-regulated protein 78 KDaGSglucose starvationIndo-1Indo-1-AMIRE1inositol requiring enzyme 1LC3Bmicrotubule- associated protein 1 light chain 3BLKB1liver kinase B1LTGLysoTracker GreenManmannoseMEFmouse embryonic fibroblastMAPKmitogen-activated protein kinasemtDNAmitochondrial DNAmTORmammalian target of rapamycinNACN-acetyl-l- cysteineOMoligomycinp53tumor protein p53p70S6K70 kDa ribosomal protein S6 kinasePERKPKR-like ER kinasePI3K IIIclass III phosphatidylinositol 3′ kinasePPPpentose phosphate pathwayROSreactive oxygen speciesSTOSTO- 609TGthapsigarginTMtunicamycinTSCtuberous sclerosis complexUPRunfolded protein response.

Original languageEnglish (US)
Pages (from-to)1463-1477
Number of pages15
JournalBiochemical Pharmacology
Volume85
Issue number10
DOIs
StatePublished - May 15 2013

Keywords

  • 2-Deoxyglucose
  • Autophagy
  • Endoplasmic reticulum stress
  • Glucose starvation
  • Hypoxia

ASJC Scopus subject areas

  • Pharmacology
  • Biochemistry

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