Interacting effects of N-terminal variation and strex exon splicing on slo potassium channel regulation by calcium, phosphorylation, and oxidation.
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.
Erxleben
Christian
C
Laboratory of Signal Transduction, NIEHS, National Institutes of Health, 111 Alexander Drive, Research Triangle Park, NC 27709, USA.
Everhart
Angela L
AL
Romeo
Charles
C
Florance
Hannah
H
Bauer
Mary Beth
MB
Alcorta
David A
DA
Rossie
Sandra
S
Shipston
Michael J
MJ
Armstrong
David L
DL
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
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