Axonal distribution of mitochondria maintains neuronal autophagy during aging via eIF2β

Abstract

SummaryNeuronal aging and neurodegenerative diseases are accompanied by proteostasis collapse, while cellular factors that trigger it are not identified. Impaired mitochondrial transport in the axon is another feature of aging and neurodegenerative diseases. UsingDrosophila, we found that genetic depletion of axonal mitochondria causes dysregulation of translation and protein degradation. Axons with mitochondrial depletion showed abnormal protein accumulation, and autophagic defects. Lowering neuronal ATP levels by blocking glycolysis did not reduce autophagy, suggesting that autophagic defects are associated with mitochondrial distribution. We found eIF2β was upregulated by depletion of axonal mitochondria via proteome analysis. Phosphorylation of eIF2α, another subunit of eIF2, was lowered, and global translation was suppressed. Neuronal overexpression ofeIF2βphenocopied the autophagic defects and neuronal dysfunctions, and loweringeIF2βexpression rescued those perturbations caused by depletion of axonal mitochondria. These results indicate the mitochondria-eIF2β axis maintains proteostasis in the axon, of which disruption may underly the onset and progression of age-related neurodegenerative diseases.HighlightsLoss of axonal mitochondria impairs autophagy and accumulates proteins in the axonLoss of axonal mitochondria upregulates eIF2β and downregulates p-eIF2αNeuronal upregulation of eIF2β induces autophagic defects and locomotor dysfunctionLowering eIF2β rescues autophagic defects caused by loss of axonal mitochondria