Functionally diverse complement of large conductance calcium- and voltage-activated potassium channel (BK) alpha-subunits generated from a single site of splicing.
The pore-forming alpha-subunits of large conductance calcium- and voltage-activated potassium (BK) channels are encoded by a single gene that undergoes extensive alternative pre-mRNA splicing. However, the extent to which differential exon usage at a single site of splicing may confer functionally distinct properties on BK channels is largely unknown. Here we demonstrated that alternative splicing at site of splicing C2 in the mouse BK channel C terminus generates five distinct splice variants: ZERO, e20, e21(STREX), e22, and a novel variant deltae23. Splice variants display distinct patterns of tissue distribution with e21(STREX) expressed at the highest levels in adult endocrine tissues and e22 at embryonic stages of mouse development. deltae23 is not functionally expressed at the cell surface and acts as a dominant negative of cell surface expression by trapping other BK channel splice variant alpha-subunits in the endoplasmic reticulum and perinuclear compartments. Splice variants display a range of biophysical properties. e21(STREX) and e22 variants display a significant left shift (>20 mV at 1 microM [Ca2+]i) in half-maximal voltage of activation compared with ZERO and e20 as well as considerably slower rates of deactivation. Splice variants are differentially sensitive to phosphorylation by endogenous cAMP-dependent protein kinase; ZERO, e20, and e22 variants are all activated, whereas e21 (STREX) is the only variant that is inhibited. Thus alternative pre-mRNA splicing from a single site of splicing provides a mechanism to generate a physiologically diverse complement of BK channel alpha-subunits that differ dramatically in their tissue distribution, trafficking, and regulation.
Chen
Lie
L
Centre for Integrative Physiology, Membrane Biology Group, University of Edinburgh, Hugh Robson Building, Edinburgh EH8 9XD, Scotland, United Kingdom.
Tian
Lijun
L
MacDonald
Stephen H-F
SH
McClafferty
Heather
H
Hammond
Martin S L
MS
Huibant
Jean-Marc
JM
Ruth
Peter
P
Knaus
Hans-Guenther
HG
Shipston
Michael J
MJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D019143:Evolution, Molecular; D005091:Exons; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007150:Immunohistochemistry; D007438:Introns; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011233:Precipitin Tests; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D051036:Large-Conductance Calcium-Activated Potassium Channels; D021122:Protein Subunits; D012333:RNA, Messenger