title: Heterogeneity in the properties of NEFL mutants causing Charcot-Marie-Tooth disease results in differential effects on neurofilament assembly and susceptibility to intervention by the chaperone-inducer, celastrol.
abstract: Aberrant aggregation of neurofilament proteins is a common feature of neurodegenerative diseases. For example, neurofilament light protein (NEFL) mutants causing Charcot-Marie-Tooth disease induce misassembly of neurofilaments. This study demonstrated that mutations in different functional domains of NEFL have different effects on filament assembly and susceptibility to interventions to restore function. The mouse NEFL mutants, NEFL(Q333P) and NEFL(P8R), exhibited different assembly properties in SW13-cells, cells lacking endogenous intermediate filaments, indicating different consequences of these mutations on the biochemical properties of NEFL. The p.Q333P mutation caused reversible misfolding of the protein. NEFL(Q333P) could be refolded and form coil-coiled dimers, in vitro using chaotropic agent, and in cultured cells by induction of HSPA1 and HSPB1. Celastrol, an inducer of chaperone proteins, induced HSPA1 expression in motor neurons and prevented the formation of neurofilament inclusions and mitochondrial shortening induced by expression of NEFL(Q333P), but not in sensory neurons. Conversely, celastrol had a protective effect against the toxicity of NEFL(P8R), a mutant which is sensitive to HSBP1 but not HSPA1 chaperoning, only in large-sized sensory neurons, not in motor neurons. Importantly, sensory and motor neurons do not respond identically to celastrol and different chaperones are upregulated by the same treatment. Thus, effective therapy of CMT not only depends on the identity of the mutated gene, but the consequences of the specific mutation on the properties of the protein and the neuronal population targeted.
authors.affiliation: Department of Neurology/Neurosurgery and Montreal Neurological Institute, Montreal, QC, Canada. benoit.gentil@mcgill.ca
authors.forename: Benoit J
authors.initials: BJ
authors.lastname: Gentil
authors.forename: Walter E
authors.initials: WE
authors.lastname: Mushynski
authors.forename: Heather D
authors.initials: HD
authors.lastname: Durham
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics*; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis; D006360:Heat-Shock Proteins; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D018832:Molecular Chaperones; D009046:Motor Neurons / Q000378:metabolism; D016900:Neurofilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053978:Pentacyclic Triterpenes; D017510:Protein Folding; D011984:Sensory Receptor Cells / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology
chemical_list: D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C525621:HSPA1B protein, human; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; C097210:Hspa1a protein, rat; D018832:Molecular Chaperones; D016900:Neurofilament Proteins; D053978:Pentacyclic Triterpenes; D014315:Triterpenes; C044882:neurofilament protein L; C050414:celastrol