Development of selective nutrient deprivation as a system to study autophagy induction and regulation in neurons.

Autophagy is emerging as a fundamentally important pathway for countering misfolded protein stress in the central nervous system. Indeed, many studies suggest that upregulation of a properly functioning macroautophagy pathway can be neuroprotective in neurodegenerative disorders characterized by the production of toxic protein conformers. Despite these advances, little is known about how autophagy is regulated in neurons. To directly study neuronal autophagy, we developed a primary neuron culture system where we can induce autophagy by withdrawal of a key supplement from the culture medium. We recently reported that the absence of insulin from the culture medium induces autophagy in this primary neuron system, and that the neuronal autophagy activation is mTOR-dependent. Further studies indicate that our nutrient-deprivation method of autophagy induction yields normally functioning and fully progressing autophagy based upon treatment with lysosomal inhibitors. As this method of autophagy induction can protect neurons from proteotoxic cell death, our findings suggest that an understanding of how to turn on autophagy in neurons could translate into a viable approach for treating neurodegenerative proteinopathies. However, before therapeutic applications can be realized, the pathways regulating neuronal autophagy need to be defined. As highlighted herein, our system for autophagy induction should contribute to efforts aimed at understanding the regulatory basis of autophagy activation in neurons.