17beta-Estradiol upregulates distinct maxi-K channel transcripts in mouse uterus.
The mouse maxi-K channel transcript undergoes alternative splicing to produce isoforms differing in sensitivity to intracellular regulators. We hypothesized that 17beta-estradiol could induce myometrial maxi-K channel transcripts to differentially splice. Polymerase chain reaction demonstrated two products at site D in mice injected with either 8.5 microg of 17beta-estradiol for 4 days or a vehicle control. Splicing of site D is known to modulate the sensitivity of the maxi-K channel to calcium and voltage. RNase protection analyses revealed that the alpha subunit transcript, and an exon encoding 59 amino acids at site D that enhances Ca(2+)- and voltage-sensitivity, are upregulated approximately 1.4-fold after 17beta-estradiol stimulation however, the insertless isoform of this transcript is enhanced approximately 5-fold. Immunoblotting demonstrates that the total maxi-K channel alpha subunit expression mimics transcript regulation. These findings verify that maxi-K channel transcripts are differentially spliced by 17beta-estradiol, which may contribute to stoichiometric changes in isoform expression during pregnancy.
Holdiman
Amanda J
AJ
Department of Physiology and Biophysics, 5-660 Bowen Science Building, University of Iowa, Iowa City, IA 52242, USA.
Fergus
Daniel J
DJ
England
Sarah K
SK
D017398:Alternative Splicing / Q000187:drug effects*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005091:Exons / Q000235:genetics; D005260:Female; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D008969:Molecular Sequence Data; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics*; D021122:Protein Subunits; D014158:Transcription, Genetic; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism
D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D021122:Protein Subunits; D004958:Estradiol; D002118:Calcium