title: Cdk5 phosphorylation of huntingtin reduces its cleavage by caspases: implications for mutant huntingtin toxicity.
abstract: Huntington's disease (HD) is a neurodegenerative disorder caused by an expanded polyglutamine (polyQ) tract in the huntingtin (htt) protein. Mutant htt toxicity is exposed after htt cleavage by caspases and other proteases release NH(2)-terminal fragments containing the polyQ expansion. Here, we show htt interacts and colocalizes with cdk5 in cellular membrane fractions. Cdk5 phosphorylates htt at Ser434, and this phosphorylation reduces caspase-mediated htt cleavage at residue 513. Reduced mutant htt cleavage resulting from cdk5 phosphorylation attenuated aggregate formation and toxicity in cells expressing the NH(2)-terminal 588 amino acids (htt588) of mutant htt. Cdk5 activity is reduced in the brains of HD transgenic mice compared with controls. This result can be accounted for by the polyQ-expanded htt fragments reducing the interaction between cdk5 and its activator p35. These data predict that the ability of cdk5 phosphorylation to protect against htt cleavage, aggregation, and toxicity is compromised in cells expressing toxic fragments of htt.
authors.affiliation: Department of Medical Genetics, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, CB2 2XY, England, UK.
authors.forename: Shouqing
authors.initials: S
authors.lastname: Luo
authors.forename: Coralie
authors.initials: C
authors.lastname: Vacher
authors.forename: Janet E
authors.initials: JE
authors.lastname: Davies
authors.forename: David C
authors.initials: DC
authors.lastname: Rubinsztein
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics*; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism
chemical_list: C086055:HTT protein, human; C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010455:Peptides; C097188:polyglutamine; D012694:Serine; D051360:Cyclin-Dependent Kinase 5; C495905:CDK5 protein, human; C495906:Cdk5 protein, mouse; D018844:Cyclin-Dependent Kinases; D020169:Caspases