Journal
CELL DEATH AND DIFFERENTIATION
Volume 14, Issue 2, Pages 230-239Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/sj.cdd.4401984
Keywords
polyglutamine; ER stress; autophagy; eIF2 alpha; caspase-12
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Funding
- NIDDK NIH HHS [DK42394] Funding Source: Medline
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Expanded polyglutamine 72 repeat (polyQ72) aggregates induce endoplasmic reticulum (ER) stress-mediated cell death with caspase-12 activation and vesicular formation (autophagy). We examined this relationship and the molecular mechanism of autophagy formation. Rapamycin, a stimulator of autophagy, inhibited the polyQ72-induced cell death with caspase-12 activation. PolyQ72, but not polyQ11, stimulated Atg5-Atg12-Atg16 complex-dependent microtubule-associated protein 1 (MAP1) light chain 3 (LC3) conversion from LC3-I to -II, which plays a key role in autophagy. The eucaryotic translation initiation factor 2 a (eIF2 alpha) A/A mutation, a knock-in to replace a phosphorylatable Ser(51) with Ala(51), and dominant-negative PERK inhibited polyQ72-induced LC3 conversion. PolyQ72 as well as ER stress stimulators upregulated Atg12 mRNA and proteins via eIF2 alpha phosphorylation. Furthermore, Atg5 deficiency as well as the eIF2 alpha A/A mutation increased the number of cells showing polyQ72 aggregates and polyQ72-induced caspase-12 activation. Thus, autophagy formation is a cellular defense mechanism against polyQ72-induced ER-stress-mediated cell death by degrading polyQ72 aggregates, with PERK/eIF2 alpha phosphorylation being involved in polyQ72-induced LC3 conversion.
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