Let-7 and induced autophagy. Mus musculus

Macroautophagy (hereafter autophagy) is the major pathway by which macromolecules and organelles are degraded. Autophagy is regulated by the mTOR signaling pathway, which is the focal point for integration of metabolic information, with mTORC1 playing a central role in balancing biosynthesis and catabolism. Of the various inputs to mTORC1, the amino acid sensing pathway is among the most potent. Based upon transcriptome analysis of neurons subjected to nutrient deprivation, we identified let-7 as a microRNA capable of promoting neuronal autophagy. We found that let-7 activates autophagy by coordinately down-regulating the amino acid sensing pathway to prevent mTORC1 activation. Let-7 induced autophagy in the brain and greatly reduced protein aggregates in a lentivirus model of polyglutamine disease, establishing the physiological relevance of let-7 for in vivo autophagy modulation. Moreover, peripheral delivery of let-7 anti-miR repressed autophagy in muscle and white fat, suggesting that let-7 autophagy regulation extends beyond the CNS. Hence, let-7 plays a central role in nutrient homeostasis and proteostasis regulation in higher organisms. Overall design: anti-let7 treated cortices and hippocampi