title: Molecular mechanisms underlying the apoptotic effect of KCNB1 K+ channel oxidation.
abstract: Potassium (K(+)) channels are targets of reactive oxygen species in the aging nervous system. KCNB1 (formerly Kv2.1), a voltage-gated K(+) channel abundantly expressed in the cortex and hippocampus, is oxidized in the brains of aging mice and of the triple transgenic 3xTg-AD mouse model of Alzheimer's disease. KCNB1 oxidation acts to enhance apoptosis in mammalian cell lines, whereas a KCNB1 variant resistant to oxidative modification, C73A-KCNB1, is cytoprotective. Here we investigated the molecular mechanisms through which oxidized KCNB1 channels promote apoptosis. Biochemical evidence showed that oxidized KCNB1 channels, which form oligomers held together by disulfide bridges involving Cys-73, accumulated in the plasma membrane as a result of defective endocytosis. In contrast, C73A-mutant channels, which do not oligomerize, were normally internalized. KCNB1 channels localize in lipid rafts, and their internalization was dynamin 2-dependent. Accordingly, cholesterol supplementation reduced apoptosis promoted by oxidation of KCNB1. In contrast, cholesterol depletion exacerbated apoptotic death in a KCNB1-independent fashion. Inhibition of raft-associating c-Src tyrosine kinase and downstream JNK kinase by pharmacological and molecular means suppressed the pro-apoptotic effect of KCNB1 oxidation. Together, these data suggest that the accumulation of KCNB1 oligomers in the membrane disrupts planar lipid raft integrity and causes apoptosis via activating the c-Src/JNK signaling pathway.
authors.affiliation: University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Department of Neuroscience and Cell Biology, 683 Hoes Ln. W., Piscataway, New Jersey 08854, USA.
authors.forename: Xilong
authors.initials: X
authors.lastname: Wu
authors.forename: Berenice
authors.initials: B
authors.lastname: Hernandez-Enriquez
authors.forename: Michelle
authors.initials: M
authors.lastname: Banas
authors.forename: Robin
authors.initials: R
authors.lastname: Xu
authors.forename: Federico
authors.initials: F
authors.lastname: Sesti
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis; D000081247:CSK Tyrosine-Protein Kinase; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D034285:Dynamin II / Q000235:genetics / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System; D021962:Membrane Microdomains / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D020125:Mutation, Missense; D010084:Oxidation-Reduction; D055503:Protein Multimerization; D051669:Shab Potassium Channels / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C496990:Kcnb1 protein, mouse; D051669:Shab Potassium Channels; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D048670:MAP Kinase Kinase 4; D034285:Dynamin II