The large conductance potassium channel beta-subunit can interact with and modulate the functional properties of a calcium-activated chloride channel, CLCA1.
We have recently compared the biophysical and pharmacological properties of native Ca(2+)-activated Cl(-) currents in murine portal vein with mCLCA1 channels cloned from murine portal vein myocytes (Britton, F. C., Ohya, S., Horowitz, B., and Greenwood, I. A. (2002) J. Physiol. (Lond.) 539, 107-117). These channels shared a similar relative permeability to various anions, but the expressed channel current lacked the marked time dependence of the native current. In addition, the expressed channel showed a lower Ca(2+) sensitivity than the native channel. As non-pore-forming regulatory beta-subunits alter the kinetics and increase the Ca(2+) sensitivity of Ca(2+)-dependent K(+) channels (BK channels) we investigated whether co-expression of beta-subunits with CLCA1 would alter the kinetics/Ca(2+) sensitivity of mCLCA1. Internal dialysis of human embryonic kidney cells stably expressing CLCA1 with 500 nM Ca(2+) evoked a significantly larger current when the beta-subunit KCNMB1 was co-expressed. In a small number of co-transfected cells marked time dependence to the activation kinetics was observed. Interaction studies using the mammalian two-hybrid technique demonstrated a physical association between CLCA1 and KCNMB1 when co-expressed in human embryonic kidney cells. These data suggest that activation of CLCA1 can be modified by accessory subunits.
Greenwood
Iain A
IA
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557-0046, USA.
Miller
Lisa J
LJ
Ohya
Susumu
S
Horowitz
Burton
B
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018118:Chloride Channels / Q000737:chemistry* / Q000502:physiology; D002713:Chlorine / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D007700:Kinetics; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D051379:Mice; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry*; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D020798:Two-Hybrid System Techniques
C492109:CLCA1 protein, human; D018118:Chloride Channels; C116464:Clca3a1 protein, mouse; D018076:DNA, Complementary; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D002713:Chlorine; D011188:Potassium; D002118:Calcium