A Neuroprotective Function of NSF1 Sustains Autophagy and Lysosomal Trafficking inDrosophila

Abstract

A common feature of many neurodegenerative diseases is the accumulation of toxic proteins that disrupt vital cellular functions. Degradative pathways such as autophagy play an important protective role in breaking down misfolded and long-lived proteins. Neurons are particularly vulnerable to defects in these pathways, but many of the details regarding the link between autophagy and neurodegeneration remain unclear. We previously found that temperature-sensitive paralytic mutants in Drosophila are enriched for those exhibiting age-dependent neurodegeneration. Here we show that one of these mutants, comatose (comt), in addition to locomotor defects, displays shortened lifespan and progressive neurodegeneration, including loss of dopaminerigic (DA) neurons. comt encodes Nethyl-maleimide sensitive fusion protein (NSF1), which has a well-documented role in synaptic transmission. However, the neurodegenerative phenotypes we observe in comt mutants do not appear to depend on defects in synaptic transmission, but rather from their inability to sustain autophagy under stress, due at least in part to a defect in trafficking of lysosomal proteases such as cathepsin-L. Conversely, overexpression of NSF1 rescues a-synuclein-induced toxicity of DA neurons in a model of Parkinson's disease. Our results demonstrate a neuroprotective role for NSF1 that involves mediation of fusion events crucial for degradative pathways such as autophagy, providing greater understanding of cellular dysfunctions common to several neurodegenerative diseases.

Transcellular spreading of huntingtin aggregates in theDrosophilabrain

“…To test the requirement of SNARE-mediated fusion events in the spread of Htt aggregates throughout the Drosophila brain, we knocked down expression of NSF1, encoded by comatose (comt). NSF1 is required for the disassembly and recycling of SNARE complexes involved in synaptic transmission (32)(33)(34) and is also required for fusion events involving lysosomal trafficking and autophagy (35). To inhibit NSF1 function in neurons expressing UAS-mRFP.…”

“…Immunohistochemistry was performed as previously described (35). Brains were dissected in PBS and fixed in 4% (vol/vol) formaldehyde at room temperature for 20 min.…”

The crucial impact of lysosomes in aging and longevity

“…Accordingly, mxl-3 mutant animals are long-lived (O’Rourke and Ruvkun, 2013). In D. melanogaster , overexpression of N-ethyl-maleimide sensitive fusion protein (NSF1) prevents neurodegeneration in a model of age-related Parkinson's disease, possibly by sustaining trafficking of lysosomal proteases and autophagy (Babcock et al, 2015). Collectively, these examples show the protective potential of increasing lysosomal performance under aging conditions.…”

De novo NSF mutations cause early infantile epileptic encephalopathy

“…Besides playing roles in intracellular vesicle transport and synaptic transmission of neurotransmitters, neurogenesis, and neuroprotection, NSF may also play a role in the epileptic phenotype. Drosophila carrying mutant NSF/comt exhibited a reduced life‐span and progressive neurodegeneration of the dopaminergic neurons, suggesting involvement of NSF in autophagy and neuroprotection . Moreover, the lethal mutation in comt resulted in a reduction in the size and branching of synapses, suggesting that NSF plays a critical role in neurogenesis .…”