NDR1/2 Kinases Enhance Autophagy and Prevent Neurodegeneration via ATG9A Trafficking

NDR kinases NDR1 and NDR2 are highly conserved regulators of neuronal differentiation that are also implicated in mitochondrial health and autophagy. The roles of NDR1/2 in mammalian brain homeostasis in vivo have not been explored. Using constitutive Ndr1 and/or neuron-specific Ndr2 knockout mouse models we show that, dual, but not individual loss of Ndr1/2 causes neurodegeneration with progressive accumulation of p62 and ubiquitinated proteins. Consistent with impaired autophagy, we found reduced LC3-positive autophagosomes in the brain and lower autophagosome formation rates and axonal LC3 trafficking in primary neurons expressing NDR1/2 shRNA. Quantitative proteomics revealed altered regulation of membrane trafficking and identified the endocytic protein Raph1/Lamellipodin (Lpd) as a novel substrate of NDR kinases. Pronounced mislocalisation of the transmembrane autophagy protein ATG9A at the neuronal periphery, partially at synapses, impaired axonal ATG9A trafficking and increased ATG9A surface levels reflect defective endocytosis, as shown by reduced transferrin uptake. We provide mechanistic understanding of how NDR kinases maintain neuronal autophagy and health.