title: Regulation of neuronal proapoptotic potassium currents by the hepatitis C virus nonstructural protein 5A.
abstract: Apoptosis-enabling neuronal potassium efflux is mediated by an enhancement of K+ currents. In cortical neurons, increased currents are triggered by dual phosphorylation of Kv2.1 by Src and p38 at channel residues Y124 and S800. It was recently shown that a K+ current surge is also present in hepatocytes undergoing apoptosis, and that the hepatitis C virus (HCV) nonstructural protein 5A (NS5A) could inhibit Kv2.1-mediated currents and block cell death. Here, we show that NS5A1b (from HCV genotype 1b) expression in rat neurons depresses delayed rectifier potassium currents, limits the magnitude of the K+ current surge following exposure to activated microglia, and is neuroprotective. In a non-neuronal recombinant expression system, cells expressing Kv2.1 mutated at residue Y124, but not S800 mutants, are insensitive to NS5A1b-mediated current inhibition. Accordingly, NS5A1b coexpression prevents phosphorylation of wild-type Kv2.1 by Src at Y124, but is unable to inhibit p38 phosphorylation of the channel at S800. The actions of the viral protein are genotype-selective, as NS5A1a does not depress neuronal potassium currents nor inhibit Src phosphorylation of Kv2.1. Our results indicate that NS5A1b limits K+ currents following injury, leading to increased neuronal viability. NS5A1b may thus serve as a model for a new generation of neuroprotective agents.
authors: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
authors: Callie A
authors: CA
authors: Norris
authors: Kai
authors: K
authors: He
authors: Mitchell G
authors: MG
authors: Springer
authors: Karen A
authors: KA
authors: Hartnett
authors: John P
authors: JP
authors: Horn
authors: Elias
authors: E
authors: Aizenman
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D006224:Cricetinae; D003412:Cricetulus; D004558:Electric Stimulation; D004622:Embryo, Mammalian; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D017628:Microglia / Q000502:physiology; D009154:Mutation / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D051381:Rats; D051669:Shab Potassium Channels / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase
chemical_list: D049452:Green Fluorescent Proteins; D051669:Shab Potassium Channels; D017361:Viral Nonstructural Proteins; D048051:p38 Mitogen-Activated Protein Kinases; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase