Characterization and regulation of Ca2+-dependent K+  channels in human esophageal smooth muscle

We examined the properties of K+ channels in smooth muscle cells dissociated from human esophagus using patch-clamp recording in the cell-attached configuration. The predominant channel observed had a conductance of 224 ± 4 pS, and current reversal was dependent on K+ concentration. Channel activity was voltage dependent and increased with elevation of intracellular free Ca2+ concentration ([Ca2+]i), consistent with this being the large-conductance Ca2+-dependent K+(KCa) channel. ACh as well as caffeine caused transient increases in KCa channel activity, and the effects of ACh persisted in Ca2+-free solution, indicating that Ca2+ release from stores contributed to channel activation. Simultaneous patch clamp and fluorescence revealed that KCachannel activity was well correlated with elevation of [Ca2+]i. The functional role of KCachannels in esophagus was studied by measuring ACh-induced contraction of strips of muscle. Tetraethylammonium and iberiotoxin, blockers of KCa channels, increased ACh-induced contraction, consistent with a role for K+ channels in limiting excitation and contraction. These studies are the first to characterize KCa channels and their regulation in human esophageal smooth muscle.

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Complex role of STIM1 in the activation of store-independent Orai1/3 channels

The Journal of General Physiology ◽

10.1085/jgp.201311084 ◽

2014 ◽

Vol 143 (3) ◽

pp. 345-359 ◽

Cited By ~ 50

Author(s):

Xuexin Zhang ◽

Wei Zhang ◽

José C. González-Cobos ◽

Isaac Jardin ◽

Christoph Romanin ◽

...

Keyword(s):

Patch Clamp ◽

Cell Types ◽

Hek293 Cells ◽

Patch Clamp Recording ◽

Channel Activation ◽

Whole Cell ◽

Perforated Patch ◽

Crac Channels ◽

Crac Channel

Orai proteins contribute to Ca2+ entry into cells through both store-dependent, Ca2+ release–activated Ca2+ (CRAC) channels (Orai1) and store-independent, arachidonic acid (AA)-regulated Ca2+ (ARC) and leukotriene C4 (LTC4)-regulated Ca2+ (LRC) channels (Orai1/3 heteromultimers). Although activated by fundamentally different mechanisms, CRAC channels, like ARC and LRC channels, require stromal interacting molecule 1 (STIM1). The role of endoplasmic reticulum–resident STIM1 (ER-STIM1) in CRAC channel activation is widely accepted. Although ER-STIM1 is necessary and sufficient for LRC channel activation in vascular smooth muscle cells (VSMCs), the minor pool of STIM1 located at the plasma membrane (PM-STIM1) is necessary for ARC channel activation in HEK293 cells. To determine whether ARC and LRC conductances are mediated by the same or different populations of STIM1, Orai1, and Orai3 proteins, we used whole-cell and perforated patch-clamp recording to compare AA- and LTC4-activated currents in VSMCs and HEK293 cells. We found that both cell types show indistinguishable nonadditive LTC4- and AA-activated currents that require both Orai1 and Orai3, suggesting that both conductances are mediated by the same channel. Experiments using a nonmetabolizable form of AA or an inhibitor of 5-lipooxygenase suggested that ARC and LRC currents in both cell types could be activated by either LTC4 or AA, with LTC4 being more potent. Although PM-STIM1 was required for current activation by LTC4 and AA under whole-cell patch-clamp recordings in both cell types, ER-STIM1 was sufficient with perforated patch recordings. These results demonstrate that ARC and LRC currents are mediated by the same cellular populations of STIM1, Orai1, and Orai3, and suggest a complex role for both ER-STIM1 and PM-STIM1 in regulating these store-independent Orai1/3 channels.

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Functional role of miRNA-34A in smooth muscle cell functions and neointima formation

Atherosclerosis ◽

10.1016/j.atherosclerosis.2015.10.060 ◽

2016 ◽

Vol 244 ◽

pp. e3-e4 ◽

Cited By ~ 1

Author(s):

F. Yang ◽

Q. Chen ◽

G. Wen ◽

C. Zhang ◽

L.A. Luong ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cell ◽

Muscle Cell ◽

Functional Role ◽

Neointima Formation ◽

Cell Functions

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Ketamine blocks Ca2+-activated K+ channels in rabbit cerebral arterial smooth muscle cells

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00194.2003 ◽

2003 ◽

Vol 285 (3) ◽

pp. H1347-H1355 ◽

Cited By ~ 8

Author(s):

Jin Han ◽

Nari Kim ◽

Hyun Joo ◽

Euiyong Kim

Keyword(s):

Smooth Muscle ◽

Patch Clamp ◽

Smooth Muscle Cells ◽

Cerebral Arteries ◽

Muscle Cells ◽

Channel Activity ◽

Patch Clamp Technique ◽

Arterial Smooth Muscle ◽

Clamp Technique ◽

Arterial Smooth Muscle Cells

Although ketamine and Ca2+-activated K+ (KCa) channels have been implicated in the contractile activity regulation of cerebral arteries, no studies have addressed the specific interactions between ketamine and the KCa channels in cerebral arteries. The purpose of this study was to examine the direct effects of ketamine on KCa channel activities using the patch-clamp technique in single-cell preparations of rabbit middle cerebral arterial smooth muscle. We tested the hypothesis that ketamine modulates the KCa channel activity of the cerebral arterial smooth muscle cells of the rabbit. Vascular myocytes were isolated from rabbit middle cerebral arteries using enzymatic dissociation. Single KCa channel activities of smooth muscle cells from rabbit cerebral arteries were recorded using the patch-clamp technique. In the inside-out patches, ketamine in the micromolar range inhibited channel activity with a half-maximal inhibition of the ketamine conentration value of 83.8 ± 12.9 μM. The Hill coefficient was 1.2 ± 0.3. The slope conductance of the current-voltage relationship was 320.1 ± 2.0 pS between 0 and +60 mV in the presence of ketamine and symmetrical 145 mM K+. Ketamine had little effect on either the voltage-dependency or open- and closed-time histograms of KCa channel. The present study clearly demonstrates that ketamine inhibits KCa channel activities in rabbit middle cerebral arterial smooth muscle cells. This inhibition of KCa channels may represent a mechanism for ketamine-induced cerebral vasoconstriction.

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