title: SIMPLE interacts with NEDD4 and TSG101: evidence for a role in lysosomal sorting and implications for Charcot-Marie-Tooth disease.
abstract: Mutation of the SIMPLE gene (small integral membrane protein of the lysosome/late endosome) is the molecular basis of Charcot-Marie-Tooth disease type 1C (CMT1C), a demyelinating peripheral neuropathy. Although the precise function of SIMPLE is unknown, prior reports suggest it localizes to the lysosome/late endosome. Furthermore, murine Simple interacts with Nedd4 (neural precursor cell expressed, developmentally downregulated 4), an E3 ubiquitin ligase that is important for regulating lysosomal degradation of plasma membrane proteins. To bring insights into the biochemical function of human SIMPLE, we confirmed that human SIMPLE interacts with NEDD4 and also report a novel interaction with tumor susceptibility gene 101 (TSG101), a class E vacuolar sorting protein. TSG101 is known to function downstream of NEDD4, sorting ubiquitinated substrates into multivesicular bodies (MVBs), which then deliver their cargo into the lysosomal lumen for degradation. Given the interaction with NEDD4 and TSG101, and the localization of SIMPLE along the lysosomal degradation pathway, we hypothesize that SIMPLE plays a role in the lysosomal sorting of plasma membrane proteins. We examine three CMT1C-associated SIMPLE mutations and show that they do not affect the interaction with NEDD4 or TSG101, nor do they lead to altered subcellular localization.
authors.affiliation: Department of Pediatrics, Division of Genetics and Developmental Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Shirk
authors.forename: Susan K
authors.initials: SK
authors.lastname: Anderson
authors.forename: Sayed H
authors.initials: SH
authors.lastname: Hashemi
authors.forename: Phillip F
authors.initials: PF
authors.lastname: Chance
authors.forename: Craig L
authors.initials: CL
authors.lastname: Bennett
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular / Q000379:methods; D004268:DNA-Binding Proteins / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000502:physiology; D005455:Fluorescent Antibody Technique / Q000379:methods; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D052118:Lysosomal-Associated Membrane Protein 1 / Q000378:metabolism; D008247:Lysosomes / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D000075702:Nedd4 Ubiquitin Protein Ligases; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection / Q000379:methods; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000099177:Tsg101 Protein
chemical_list: D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D052118:Lysosomal-Associated Membrane Protein 1; D000075702:Nedd4 Ubiquitin Protein Ligases; D009687:Nuclear Proteins; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; D000099177:Tsg101 Protein; C118738:LITAF protein, human; C000618483:Nedd4 protein, human