Neurons rely on autophagy to constitutively degrade damaged proteins and organelles to maintain neuronal homeostasis. When neuronal autophagy capacity is overwhelmed, aggregated proteins and damaged organelles accumulate and contribute to neuronal dysfunction or death. Indeed, autophagy dysfunction is consistently associated with neurodegenerative diseases, such as Parkinson’s Disease. How do neurons respond when faced with the accumulation of dysfunctional proteins and organelles that overwhelm autophagy? Do neurons employ alternate quality control mechanisms? Recent findings suggest that autophagy-dependent degradation and autophagy-dependent secretion can act in coordination to regulate cellular homeostasis in non-neuronal cell types. When autophagosome maturation is impeded, autophagy-dependent secretion of extracellular vesicles (EVs) can be initiated as a mechanism to unburden the degrative machinery. Whether neurons similarly extrude damaged material via autophagy dependent secretion is unclear. I hypothesize that stressed neurons engage autophagy-dependent secretion as an alternate quality control mechanism to dispel cellular waste, e.g., mitochondria, which is then internalized by surrounding astrocytes. This model is supported by my preliminary findings that neurons with reduced capacity for autophagy upregulate secretion of EVs. Of particular interest, I find that mitochondrial proteins are shunted from degradation toward a secretory fate in chronically stressed neurons. These observations have important implications in neurodegenerative diseases where autophagy is strained, and the expulsion of mitochondria could heighten systemic inflammatory responses. This proposal will contribute to our fundamental understanding of neuronal homeostasis mechanisms and could reveal important clues underlying neurodegenerative disease. In Aim 1, I test the hypothesis that stressed neurons shunt autophagy cargo toward secretion via secretory autophagy. I will track secretion of EVs from neurons facing chronic or acute autophagic stress and determine which autophagy proteins are required for compensatory secretion. Using immunoblotting and high-resolution microscopy, I will confirm the secretory autophagy pathway prompting secretion in stressed neurons. Finally, I will use proteomics to molecularly profile the cargo expelled via autophagy dependent secretion. In Aim 2, I test the hypothesis that neurons expel mitochondria for transcellular internalization. I will use neuronal- astrocyte co-culture to visualize neuronal mitochondria internalized by nearby astrocytes. Next, I will track astrocyte engulfment of neuronal mitochondria in vivo.