title: Phosphorylation of arfaptin 2 at Ser260 by Akt Inhibits PolyQ-huntingtin-induced toxicity by rescuing proteasome impairment.
abstract: Huntington disease (HD) is caused by an abnormal expanded polyglutamine repeat in the huntingtin protein. Insulin-like growth factor-1 is of particular interest in HD because it strongly inhibits polyQ-huntingtin-induced neurotoxicity. This neuroprotective effect involves the phosphorylation of huntingtin at Ser(421) by the prosurvival kinase Akt (Humbert, S., Bryson, E. A., Cordelieres, F. P., Connors, N. C., Datta, S. R., Finkbeiner, S., Greenberg, M. E., and Saudou, F. (2002) Dev. Cell 2, 831-837). Here, we report that Akt inhibits polyQ-huntingtin-induced toxicity in the absence of phosphorylation of huntingtin at Ser(421), suggesting that Akt also acts on other downstream effector(s) to prevent neuronal death in HD. We show that this survival effect involves the ADP-ribosylation factor-interacting protein arfaptin 2, the levels of which are increased in HD patients. Akt phosphorylated arfaptin 2 at Ser(260). Lack of phosphorylation of arfaptin 2 at this site substantially modified its subcellular distribution and increased neuronal death and intranuclear inclusions caused by polyQ-huntingtin. In contrast, arfaptin 2 had a neuroprotective effect on striatal neurons when phosphorylated by Akt. This effect is mediated through the proteasome, as phosphorylated arfaptin 2 inhibited the blockade of the proteasome induced by polyQ-huntingtin. This study points out a new mechanism by which Akt promotes neuroprotection in HD, emphasizing the potential therapeutic interest of this pathway in the disease.
authors.affiliation: UMR 146 CNRS/Institut Curie, Centre Universitaire, 91405 Orsay Cedex, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Rangone
authors.forename: Raúl
authors.initials: R
authors.lastname: Pardo
authors.forename: Emilie
authors.initials: E
authors.lastname: Colin
authors.forename: Jean-Antoine
authors.initials: JA
authors.lastname: Girault
authors.forename: Frédéric
authors.initials: F
authors.lastname: Saudou
authors.forename: Sandrine
authors.initials: S
authors.lastname: Humbert
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005822:Genetic Vectors; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D009474:Neurons / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry*; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine / Q000737:chemistry*; D014018:Tissue Distribution; D014162:Transfection; D015854:Up-Regulation
chemical_list: C101158:ARFIP2 protein, human; D048868:Adaptor Proteins, Signal Transducing; C086055:HTT protein, human; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D011518:Proto-Oncogene Proteins; C097188:polyglutamine; D012694:Serine; D007334:Insulin-Like Growth Factor I; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D046988:Proteasome Endopeptidase Complex