This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Autophagy is a highly regulated cellular mechanism for the bulk degradation of cytoplasmic contents. It has been implicated in a variety of physiological and pathological conditions relevant to neurological diseases. However, the regulation of autophagy in neurons and its role in neuronal and axonal pathology are not yet understood. Using transgenic mice producing the fluorescent autophagy marker LC3 (GFP-LC3), we provide molecular evidence for the involvement of autophagy in axonal dystrophy and degeneration induced by Lurcher, an excitotoxic neurodegeneration mutation. We show that in Lurcher mice, the excitotoxic insult triggers an early response of Purkinje cells involving accumulation of GFP-LC3-labeled autophagosomes in axonal dystrophic swellings, a hallmark of CNS axonopathy. In the brain, LC3 interacts primarily and with high affinity with the microtubule associated protein 1B (MAP1B). Additionally, MAP1B produced in transfected cells binds to LC3 of both cytosolic form (LC3I) and lipidated form (LC3II). Our studies further indicate that overexpression of MAP1B prevents the formation of GFP-LC3-labeled autophagosomes, and phosphorylated MAP1B is associated with GFP-LC3-labeled autophagosomes. Finally, we show that phosphorylated MAP1B is accumulated and bound to LC3 at increased level in axonal dystrophic swellings of degenerating Purkinje cells. Therefore, autophagy provides a mechanism for the degradation and remodeling of axonal structures in dystrophic and degenerating axons; prolonged activated autophagy may contribute to axonopathy during neurodegeneration.
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