A cysteine-rich domain defined by a novel exon in a slo variant in rat adrenal chromaffin cells and PC12 cells.
cDNA libraries from rat chromaffin cells and PC12 cells were screened for homologs to the mouse mSlo gene that encodes a large conductance, calcium (Ca2+)- and voltage-activated potassium channel (BK channel). One Slo variant contained sequence encoding a cysteine-rich, 59-amino acid insert for a previously described site of alternative splicing. This insert is reminiscent of zinc-finger domains. The exon was found in RNA from pancreas, anterior pituitary, cerebellum, and hippocampus. Expression in Xenopus oocytes of a Slo construct containing this exon conferred a -30 to -20 mV shift of the conductance-voltage curve. A previously uncharacterized alternative splice junction near the C-terminal end of Slo was also identified. In contrast to BK channels in rat chromaffin cells, none of the Slo variants exhibited inactivation when expressed in Xenopus oocytes. PCR screening of chromaffin cell RNA failed to reveal a homolog of an accessory beta subunit known to influence Slo channel function. Furthermore, a beta-subunit-dependent Slo channel activator, dehydrosoyasaponin I, was without effect on chromaffin cell BK current. The results argue that an accessory subunit may not be a required component of the native chromaffin cell BK channel.
Saito
M
M
Washington University School of Medicine, Department of Anesthesiology, St. Louis, Missouri 63110, USA.
Nelson
C
C
Salkoff
L
L
Lingle
C J
CJ
D000313:Adrenal Medulla / Q000378:metabolism*; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism*; D003545:Cysteine; D017931:DNA Primers; D005091:Exons; D005260:Female; D014644:Genetic Variation; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D009928:Organ Specificity; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D017931:DNA Primers; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D011994:Recombinant Proteins; D003545:Cysteine; D002118:Calcium