Neurofilament accumulation disrupts autophagy in giant axonal neuropathy

Neurofilament accumulation is a marker of several neurodegenerative diseases, but it is the primary pathology in Giant Axonal Neuropathy (GAN). This childhood onset autosomal recessive disease is caused by loss-of-function mutations in gigaxonin, the E3 adaptor protein that is essential for neurofilament degradation. Using a combination of genetic and RNA interference (RNAi) approaches, we found that dorsal root ganglia from mice lacking gigaxonin have impaired autophagy and lysosomal degradation through two mechanisms. First, neurofilament accumulations interfere with the distribution of autophagic organelles, impairing their maturation and fusion with lysosomes. Second, the accumulations sequester the chaperone 14-3-3, a protein responsible for the localization of the transcription factor EB (TFEB), a key regulator of autophagy. This dual disruption of autophagy likely contributes to the pathogenesis of other neurodegenerative diseases with neurofilament accumulations.