title: Charcot-Marie-Tooth type 2B disease-causing RAB7A mutant proteins show altered interaction with the neuronal intermediate filament peripherin.
abstract: Charcot-Marie-Tooth type 2B (CMT2B) is a peripheral ulcero-mutilating neuropathy caused by four missense mutations in the rab7a gene. CMT2B is clinically characterized by prominent sensory loss, distal muscle weakness leading to muscle atrophy, high frequency of foot ulcers and infections that often results in toe amputations. RAB7A is a ubiquitous small GTPase, which controls transport to late endocytic compartments. Although the biochemical and functional properties of disease-causing RAB7A mutant proteins have been investigated, it is not yet clear how the disease originates. To understand how mutations in a ubiquitous protein specifically affect peripheral neurons, we performed a two-hybrid screen using a dorsal root ganglia cDNA library with the purpose of identifying RAB7A interactors specific for these cells. We identified peripherin, an intermediate filament protein expressed primarily in peripheral neurons, as a putative RAB7A interacting protein. The interaction was confirmed by co-immunoprecipitation and pull-down experiments, and established that the interaction is direct using recombinant proteins. Silencing or overexpression of wild type RAB7A changed the soluble/insoluble rate of peripherin indicating that RAB7A is important for peripherin organization and function. In addition, disease-causing RAB7A mutant proteins bind more strongly to peripherin and their expression causes a significant increase in the amount of soluble peripherin. Since peripherin plays a role not only in neurite outgrowth during development but also in axonal regeneration after injury, these data suggest that the altered interaction between disease-causing RAB7A mutants and peripherin could play an important role in CMT2B neuropathy.
authors.affiliation: Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni 165, 73100 Lecce, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Cogli
authors.forename: Cinzia
authors.initials: C
authors.lastname: Progida
authors.forename: Claire L
authors.initials: CL
authors.lastname: Thomas
authors.forename: Bradley
authors.initials: B
authors.lastname: Spencer-Dene
authors.forename: Claudia
authors.initials: C
authors.lastname: Donno
authors.forename: Giampietro
authors.initials: G
authors.lastname: Schiavo
authors.forename: Cecilia
authors.initials: C
authors.lastname: Bucci
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics*; D003599:Cytoskeleton / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000502:physiology*; D000083083:Laminopathies; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D064531:Peripherins; D010957:Plasmids / Q000235:genetics; D020671:Posterior Horn Cells / Q000502:physiology; D012313:RNA / Q000235:genetics; D034622:RNA Interference; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D000090802:rab7 GTP-Binding Proteins
chemical_list: D007381:Intermediate Filament Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C578994:PRPH protein, human; D064531:Peripherins; D011993:Recombinant Fusion Proteins; D000090802:rab7 GTP-Binding Proteins; D012313:RNA; D020558:GTP Phosphohydrolases; D020691:rab GTP-Binding Proteins