title: Interacting effects of N-terminal variation and strex exon splicing on slo potassium channel regulation by calcium, phosphorylation, and oxidation.
abstract: We have investigated the structural basis for the phenotype of a native rat Slo (rSlo) potassium channel (BK(Ca); KCNMA1) in a rat pituitary cell line, GH(4)C(1). Opposing regulation of these calcium- and voltage-activated potassium channels by cAMP- and cGMP-dependent protein kinases requires an alternatively spliced exon (strex) of 59 amino acids in the cytoplasmic C terminus of the pore-forming alpha subunit encoded by rslo. However, inclusion of this cysteine-rich exon produces a 10-fold increase in the sensitivity of the channels to inhibition by oxidation. Inclusion of the strex exon also increases channel sensitivity to stimulation by calcium, but responses in the physiological ranges of calcium and voltage require coassembly with beta(1) subunits. With strex present, however, beta(1) subunits only stimulated channels assembled from rSlo alpha subunits with a truncated N terminus beginning MDALI-. Thus N-terminal variation and strex exon splicing in rSlo interact to produce BK(Ca) channels with a physiologically relevant phenotype.
authors.affiliation: Laboratory of Signal Transduction, NIEHS, National Institutes of Health, 111 Alexander Drive, Research Triangle Park, NC 27709, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Erxleben
authors.forename: Angela L
authors.initials: AL
authors.lastname: Everhart
authors.forename: Charles
authors.initials: C
authors.lastname: Romeo
authors.forename: Hannah
authors.initials: H
authors.lastname: Florance
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Bauer
authors.forename: David A
authors.initials: DA
authors.lastname: Alcorta
authors.forename: Sandra
authors.initials: S
authors.lastname: Rossie
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shipston
authors.forename: David L
authors.initials: DL
authors.lastname: Armstrong
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003545:Cysteine / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005091:Exons; D014644:Genetic Variation; D006801:Humans; D007438:Introns; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D024681:Potassium Channels, Calcium-Activated / Q000737:chemistry* / Q000235:genetics*; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: C494841:KCNMA1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D000255:Adenosine Triphosphate; D003545:Cysteine; D010100:Oxygen; D002118:Calcium