title: Molecular chaperone Hsp110 rescues a vesicle transport defect produced by an ALS-associated mutant SOD1 protein in squid axoplasm.
abstract: Mutant human Cu/Zn superoxide dismutase 1 (SOD1) is associated with motor neuron toxicity and death in an inherited form of amyotrophic lateral sclerosis (ALS; Lou Gehrig disease). One aspect of toxicity in motor neurons involves diminished fast axonal transport, observed both in transgenic mice and, more recently, in axoplasm isolated from squid giant axons. The latter effect appears to be directly mediated by misfolded SOD1, whose addition activates phosphorylation of p38 MAPK and phosphorylation of kinesin. Here, we observe that several different oligomeric states of a fusion protein, comprising ALS-associated human G85R SOD1 joined with yellow fluorescent protein (G85R SOD1YFP), which produces ALS in transgenic mice, inhibited anterograde transport when added to squid axoplasm. Inhibition was blocked both by an apoptosis signal-regulating kinase 1 (ASK1; MAPKKK) inhibitor and by a p38 inhibitor, indicating the transport defect is mediated through the MAPK cascade. In further incubations, we observed that addition of the mammalian molecular chaperone Hsc70, abundantly associated with G85R SOD1YFP in spinal cord of transgenic mice, exerted partial correction of the transport defect, associated with diminished phosphorylation of p38. Most striking, the addition of the molecular chaperone Hsp110, in a concentration substoichiometric to the mutant SOD1 protein, completely rescued both the transport defect and the phosphorylation of p38. Hsp110 has been demonstrated to act as a nucleotide exchange factor for Hsc70 and, more recently, to be able to cooperate with it to mediate protein disaggregation. We speculate that it can cooperate with endogenous squid Hsp(c)70 to mediate binding and/or disaggregation of mutant SOD1 protein, abrogating toxicity.
authors.affiliation: Department of Neurology, and F.M. Kirby Department of Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Yuyu
authors.initials: Y
authors.lastname: Song
authors.forename: Maria
authors.initials: M
authors.lastname: Nagy
authors.forename: Weiming
authors.initials: W
authors.lastname: Ni
authors.forename: Navneet K
authors.initials: NK
authors.lastname: Tyagi
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Fenton
authors.forename: Francesc
authors.initials: F
authors.lastname: López-Giráldez
authors.forename: John D
authors.initials: JD
authors.lastname: Overton
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Horwich
authors.forename: Scott T
authors.initials: ST
authors.lastname: Brady
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D049832:Decapodiformes; D020869:Gene Expression Profiling; D050957:HSP110 Heat-Shock Proteins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000037:antagonists & inhibitors; D051379:Mice; D008822:Mice, Transgenic; D020125:Mutation, Missense / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D017510:Protein Folding; D040901:Proteomics; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
chemical_list: D001426:Bacterial Proteins; D050957:HSP110 Heat-Shock Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C000606290:SOD1 protein, human; C054562:yellow fluorescent protein, Bacteria; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D048051:p38 Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5