title: Spinocerebellar ataxia-13 Kv3.3 potassium channels: arginine-to-histidine mutations affect both functional and protein expression on the cell surface.
abstract: The voltage-gated potassium channel Kv3.3 is the causative gene of SCA13 (spinocerebellar ataxia type 13), an autosomal dominant neurological disorder. The four dominant mutations identified to date cause Kv3.3 channels to be non-functional or have altered gating properties in Xenopus oocytes. In the present paper, we report that SCA13 mutations affect functional as well as protein expression of Kv3.3 channels in a mammalian cell line. The reduced protein level of SCA13 mutants is caused by a shorter protein half-life, and blocking the ubiquitin-proteasome pathway increases the total protein of SCA13 mutants more than wild-type. SCA13 mutated amino acids are highly conserved, and the side chains of these residues play a critical role in the stable expression of Kv3.3 proteins. In addition, we show that mutant Kv3.3 protein levels could be partially rescued by treatment with the chemical chaperone TMAO (trimethylamine N-oxide) and to a lesser extent with co-expression of Kv3.1b. Thus our results suggest that amino acid side chains of SCA13 positions affect the protein half-life and/or function of Kv3.3, and the adverse effect on protein expression cannot be fully rescued.
authors.affiliation: Department of Biological Sciences, Fordham University, Bronx, NY 10458, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Jing
authors.initials: J
authors.lastname: Zhu
authors.forename: William B
authors.initials: WB
authors.lastname: Thornhill
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D051670:Shaw Potassium Channels / Q000235:genetics / Q000378:metabolism*; D020754:Spinocerebellar Ataxias / Q000235:genetics / Q000378:metabolism*; D013499:Surface Properties
chemical_list: C489597:KCNC1 protein, human; C489594:KCNC3 protein, human; D050505:Mutant Proteins; D016877:Oxidants; D061988:Proteasome Inhibitors; D020033:Protein Isoforms; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; D051670:Shaw Potassium Channels; D046988:Proteasome Endopeptidase Complex