scholarly journals Co-assembly of N-type Ca2+ and BK channels underlies functional coupling in rat brain

2007 ◽  
Vol 120 (6) ◽  
pp. 985-995 ◽  
Author(s):  
D. J. Loane ◽  
P. A. Lima ◽  
N. V. Marrion
Keyword(s):  
Rat Brain ◽  
Bk Channels ◽  
Functional Coupling

Opening of large-conductance calcium-activated potassium channels by the substituted benzimidazolone NS004

1994 ◽  
Vol 71 (5) ◽  
pp. 1873-1882 ◽  
Author(s):  
M. C. McKay ◽  
S. I. Dworetzky ◽  
N. A. Meanwell ◽  
S. P. Olesen ◽  
P. H. Reinhart ◽  
...  
Keyword(s):  
Rat Brain ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Outward Current ◽  
Calcium Sensitivity ◽  
Bk Channels ◽  
Gh3 Cells ◽  
Xenopus Laevis Oocytes ◽  
Planar Lipid Bilayers ◽  
Whole Cell

1. We used electrophysiological techniques to examine the effects of 5-trifluoromethyl-1-(5-chloro-2-hydroxyphenyl)-1,3-dihydro-2H-benzimidaz ole- 2-one (NS004) on large-conductance calcium-activated potassium (BK) channels. 2. We used recordings from excised membrane patches (cell-attached and inside-out single-channel configurations) and whole-cell patch-clamp recordings to examine the effects of NS004 on single BK channels and whole-cell outward currents, respectively, in rat GH3 clonal pituitary tumor cells. We also tested NS004 on voltage-clamped BK channels isolated from rat brain plasma membrane preparations and reconstituted into planar lipid bilayers. Finally, we used two-electrode voltage-clamp techniques to study the effects of NS004 on currents expressed in Xenopus laevis oocytes by the recently described Slo BK clone from Drosophila. 3. In GH3 cells and in Xenopus oocytes expressing the Slo gene product NS004 produced an increase in an iberiotoxin- or tetraethylammonium-sensitive whole-cell outward current, respectively. NS004 produced a significant increase in the activity of single GH3 cell BK channels and rat brain BK channels reconstituted into planar lipid bilayers. In both systems this was characterized by an increase in channel mean open time, a decrease in interburst interval, and an apparent increase in channel voltage/calcium sensitivity. 4. These data indicate that NS004 could be useful for investigating the biophysical and molecular properties of BK channels and for determining the functional consequences of the opening of BK channels.

scholarly journals Functional Coupling of the β1 Subunit to the Large Conductance Ca2+-Activated K+ Channel in the Absence of Ca2+

2000 ◽  
Vol 115 (6) ◽  
pp. 719-736 ◽  
Author(s):  
Crina M. Nimigean ◽  
Karl L. Magleby
Keyword(s):  
Fold Increase ◽  
Bk Channels ◽  
Burst Duration ◽  
K Channel ◽  
Functional Coupling ◽  
Open Probability ◽  
Α Subunit ◽  
Gating Kinetics ◽  
Leftward Shift ◽  
Wide Range

Coexpression of the β1 subunit with the α subunit (mSlo) of BK channels increases the apparent Ca2+ sensitivity of the channel. This study investigates whether the mechanism underlying the increased Ca2+ sensitivity requires Ca2+, by comparing the gating in 0 Ca2+i of BK channels composed of α subunits to those composed of α+β1 subunits. The β1 subunit increased burst duration ∼20-fold and the duration of gaps between bursts ∼3-fold, giving an ∼10-fold increase in open probability (Po) in 0 Ca2+i. The effect of the β1 subunit on increasing burst duration was little changed over a wide range of Po achieved by varying either Ca2+i or depolarization. The effect of the β1 subunit on increasing the durations of the gaps between bursts in 0 Ca2+i was preserved over a range of voltage, but was switched off as Ca2+i was increased into the activation range. The Ca2+-independent, β1 subunit-induced increase in burst duration accounted for 80% of the leftward shift in the Po vs. Ca2+i curve that reflects the increased Ca2+ sensitivity induced by the β1 subunit. The Ca2+-dependent effect of the β1 subunit on the gaps between bursts accounted for the remaining 20% of the leftward shift. Our observation that the major effects of the β1 subunit are independent of Ca2+i suggests that the β1 subunit mainly alters the energy barriers of Ca2+-independent transitions. The changes in gating induced by the β1 subunit differ from those induced by depolarization, as increasing Po by depolarization or by the β1 subunit gave different gating kinetics. The complex gating kinetics for both α and α+β1 channels in 0 Ca2+i arise from transitions among two to three open and three to five closed states and are inconsistent with Monod-Wyman-Changeux type models, which predict gating among only one open and one closed state in 0 Ca2+i.

scholarly journals Functional Coupling of BK Channels to NMDA Receptors in Hippocampal Dentate Gyrus

2017 ◽  
Vol 112 (3) ◽  
pp. 112a ◽  
Author(s):  
Xin Guan ◽  
Jiyuan Zhang ◽  
Qin Li ◽  
Hui-Lin Pan ◽  
Jiusheng Yan
Keyword(s):  
Dentate Gyrus ◽  
Nmda Receptors ◽  
Bk Channels ◽  
Functional Coupling ◽  
Hippocampal Dentate Gyrus

scholarly journals Proximal clustering between BK and CaV1.3 channels promotes functional coupling and BK channel activation at low voltage

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Oscar Vivas ◽  
Claudia M Moreno ◽  
Luis F Santana ◽  
Bertil Hille
Keyword(s):  
Single Molecule ◽  
Neuronal Excitability ◽  
Low Voltage ◽  
Calcium Influx ◽  
Sympathetic Neurons ◽  
Spatial Arrangement ◽  
Bk Channels ◽  
Bk Channel ◽  
Functional Coupling ◽  
Channel Activation

CaV-channel dependent activation of BK channels is critical for feedback control of both calcium influx and cell excitability. Here we addressed the functional and spatial interaction between BK and CaV1.3 channels, unique CaV1 channels that activate at low voltages. We found that when BK and CaV1.3 channels were co-expressed in the same cell, BK channels started activating near −50 mV, ~30 mV more negative than for activation of co-expressed BK and high-voltage activated CaV2.2 channels. In addition, single-molecule localization microscopy revealed striking clusters of CaV1.3 channels surrounding clusters of BK channels and forming a multi-channel complex both in a heterologous system and in rat hippocampal and sympathetic neurons. We propose that this spatial arrangement allows tight tracking between local BK channel activation and the gating of CaV1.3 channels at quite negative membrane potentials, facilitating the regulation of neuronal excitability at voltages close to the threshold to fire action potentials.

scholarly journals Structural and Functional Coupling between BK Channels and NMDA Receptors

2016 ◽  
Vol 110 (3) ◽  
pp. 289a
Author(s):  
Jiyuan Zhang ◽  
Qin Li ◽  
Xin Guan ◽  
Hui-Lin Pan ◽  
Jiusheng Yan
Keyword(s):  
Nmda Receptors ◽  
Bk Channels ◽  
Functional Coupling

scholarly journals Structural Determinants for Functional Coupling Between the β and α Subunits in the Ca2+-activated K+ (BK) Channel

2006 ◽  
Vol 127 (2) ◽  
pp. 191-204 ◽  
Author(s):  
Patricio Orio ◽  
Yolima Torres ◽  
Patricio Rojas ◽  
Ingrid Carvacho ◽  
Maria L. Garcia ◽  
...  
Keyword(s):  
Calcium Sensitivity ◽  
Bk Channels ◽  
Bk Channel ◽  
Fine Tuning ◽  
Functional Coupling ◽  
Xenopus Laevis Oocytes ◽  
Voltage Sensitivity ◽  
Patch Clamp Technique ◽  
Α Subunit ◽  
Intracellular Domains

High conductance, calcium- and voltage-activated potassium (BK, MaxiK) channels are widely expressed in mammals. In some tissues, the biophysical properties of BK channels are highly affected by coexpression of regulatory (β) subunits. The most remarkable effects of β1 and β2 subunits are an increase of the calcium sensitivity and the slow down of channel kinetics. However, the detailed characteristics of channels formed by α and β1 or β2 are dissimilar, the most remarkable difference being a reduction of the voltage sensitivity in the presence of β1 but not β2. Here we reveal the molecular regions in these β subunits that determine their differential functional coupling with the pore-forming α-subunit. We made chimeric constructs between β1 and β2 subunits, and BK channels formed by α and chimeric β subunits were expressed in Xenopus laevis oocytes. The electrophysiological characteristics of the resulting channels were determined using the patch clamp technique. Chimeric exchange of the different regions of the β1 and β2 subunits demonstrates that the NH3 and COOH termini are the most relevant regions in defining the behavior of either subunit. This strongly suggests that the intracellular domains are crucial for the fine tuning of the effects of these β subunits. Moreover, the intracellular domains of β1 are responsible for the reduction of the BK channel voltage dependence. This agrees with previous studies that suggested the intracellular regions of the α-subunit to be the target of the modulation by the β1-subunit.

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