Voltage-Dependent K + Channels as Targets of Osmosensing in Guard Cells

1998 ◽  
Vol 10 (11) ◽  
pp. 1957 ◽  
Author(s):  
Kun Liu ◽  
Sheng Luan
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Voltage Dependent

scholarly journals Voltage-Dependent K+ Channels as Targets of Osmosensing in Guard Cells

1998 ◽  
Vol 10 (11) ◽  
pp. 1957-1970 ◽  
Author(s):  
Kun Liu ◽  
Sheng Luan
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Voltage Dependent

scholarly journals AKT2/3 Subunits Render Guard Cell K+ Channels Ca2+ Sensitive

2005 ◽  
Vol 125 (5) ◽  
pp. 483-492 ◽  
Author(s):  
Natalya Ivashikina ◽  
Rosalia Deeken ◽  
Susanne Fischer ◽  
Peter Ache ◽  
Rainer Hedrich
Keyword(s):  
Guard Cell ◽  
Guard Cells ◽  
Inward Rectifier ◽  
Hek293 Cells ◽  
K Channel ◽  
Dependent Manner ◽  
Wild Type ◽  
K Channels ◽  
Isolation And Characterization ◽  
Voltage Dependent

Inward-rectifying K+ channels serve as a major pathway for Ca2+-sensitive K+ influx into guard cells. Arabidopsis thaliana guard cell inward-rectifying K+ channels are assembled from multiple K+ channel subunits. Following the recent isolation and characterization of an akt2/3-1 knockout mutant, we examined whether the AKT2/3 subunit carries the Ca2+ sensitivity of the guard cell inward rectifier. Quantification of RT-PCR products showed that despite the absence of AKT2 transcripts in guard cells of the knockout plant, expression levels of the other K+ channel subunits (KAT1, KAT2, AKT1, and AtKC1) remained largely unaffected. Patch-clamp experiments with guard cell protoplasts from wild type and akt2/3-1 mutant, however, revealed pronounced differences in Ca2+ sensitivity of the K+ inward rectifier. Wild-type channels were blocked by extracellular Ca2+ in a concentration- and voltage-dependent manner. Akt2/3-1 mutants lacked the voltage-dependent Ca2+ block, characteristic for the K+ inward rectifier. To confirm the akt2/3-1 phenotype, two independent knockout mutants, akt2-1 and akt2::En-1 were tested, demonstrating that the loss of AKT2/3 indeed affects the Ca2+ dependence of guard cell inward rectifier. In contrast to AKT2 knockout plants, AKT1, AtKC1, and KAT1 loss-of-function mutants retained Ca2+ block of the guard cell inward rectifier. When expressed in HEK293 cells, AKT2 channel displayed a pronounced susceptibility toward extracellular Ca2+, while the dominant guard cell K+ channel KAT2 was Ca2+ insensitive. Thus, we conclude that the AKT2/3 subunit constitutes the Ca2+ sensitivity of the guard cell K+ uptake channel.

The Mechanism of Ion Permeation through K+ Channels of Stomatal Guard Cells: Voltage-Dependent Block by Na+

1991 ◽  
Vol 138 (3) ◽  
pp. 326-334 ◽  
Author(s):  
Gerhard Thiel ◽  
Michael R. Blatt
Keyword(s):  
Guard Cells ◽  
Ion Permeation ◽  
K Channels ◽  
Voltage Dependent ◽  
Stomatal Guard Cells

Atypical antipsychotic olanzapine inhibits voltage-dependent K+ channels in coronary arterial smooth muscle cells

2021 ◽  
Author(s):  
Minji Kang ◽  
Jin Ryeol An ◽  
Mi Seon Seo ◽  
Hee Seok Jung ◽  
Ryeon Heo ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Atypical Antipsychotic ◽  
Muscle Cells ◽  
Arterial Smooth Muscle ◽  
K Channels ◽  
Voltage Dependent ◽  
Arterial Smooth Muscle Cells

scholarly journals Activation and Two Modes of Blockade by Strontium of Ca2+-activated K+ Channels in Goldfish Saccular Hair Cells

1998 ◽  
Vol 111 (2) ◽  
pp. 363-379 ◽  
Author(s):  
Izumi Sugihara
Keyword(s):  
Dissociation Constant ◽  
Time Constant ◽  
Hair Cells ◽  
Single Channel ◽  
Hill Coefficient ◽  
K Channels ◽  
Voltage Dependent ◽  
Time Courses ◽  
The Hill ◽  
Inside Out

Effects of internal Sr2+ on the activity of large-conductance Ca2+-activated K+ channels were studied in inside-out membrane patches from goldfish saccular hair cells. Sr2+ was approximately one-fourth as potent as Ca2+ in activating these channels. Although the Hill coefficient for Sr2+ was smaller than that for Ca2+, maximum open-state probability, voltage dependence, steady state gating kinetics, and time courses of activation and deactivation of the channel were very similar under the presence of equipotent concentrations of Ca2+ and Sr2+. This suggests that voltage-dependent activation is partially independent of the ligand. Internal Sr2+ at higher concentrations (>100 μM) produced fast and slow blockade both concentration and voltage dependently. The reduction in single-channel amplitude (fast blockade) could be fitted with a modified Woodhull equation that incorporated the Hill coefficient. The dissociation constant at 0 mV, the Hill coefficient, and zd (a product of the charge of the blocking ion and the fraction of the voltage difference at the binding site from the inside) in this equation were 58–209 mM, 0.69–0.75, 0.45–0.51, respectively (n = 4). Long shut events (slow blockade) produced by Sr2+ lasted ∼10–200 ms and could be fitted with single-exponential curves (time constant, τl−s) in shut-time histograms. Durations of burst events, periods intercalated by long shut events, could also be fitted with single exponentials (time constant, τb). A significant decrease in τb and no large changes in τl−s were observed with increased Sr2+ concentration and voltage. These findings on slow blockade could be approximated by a model in which single Sr2+ ions bind to a blocking site within the channel pore beyond the energy barrier from the inside, as proposed for Ba2+ blockade. The dissociation constant at 0 mV and zd in the Woodhull equation for this model were 36–150 mM and 1–1.8, respectively (n = 3).

scholarly journals Block of squid axon K channels by internally and externally applied barium ions.

1982 ◽  
Vol 80 (5) ◽  
pp. 663-682 ◽  
Author(s):  
C M Armstrong ◽  
R P Swenson ◽  
S R Taylor
Keyword(s):  
Time Constant ◽  
Recovery Time ◽  
Pulse Voltage ◽  
Squid Axon ◽  
Barium Ions ◽  
K Channels ◽  
Voltage Dependent ◽  
One Step ◽  
Dissociation Constant Kd ◽  
The Way

We have studied the interactions of Ba ion with K channels. Ba2+ blocks these channels when applied either internally or externally in millimolar concentrations. Periodic depolarizations enhance block with internal Ba2+, but diminish the block caused by external Ba2+. At rest, dissociation of Ba2+ from blocked channels is very slow, as ascertained by infrequent test pulses applied after washing Ba2+ form either inside or outside. The time constant for recovery from internal and external Ba2+ is the same. Frequent pulsing greatly shortens recovery time constant after washing away both Ba2+in and Ba2+out. Block by Ba2+ applied internally or externally is voltage dependent. Internal Ba2+ block behaves like a one-step reaction governed by a dissociation constant (Kd) that decreases e-fold/12 mV increase of pulse voltage: block deepens with more positive pulse voltage. For external Ba2+, Kd decreases e-fold/18 mV as holding potential is made more negative: block deepens with increasing negativity. Millimolar external concentrations of some cations can either lessen (K+) or enhance (NH+4, Cs+) block by external Ba2+. NH+4 apparently enhances block by slowing exist of Ba ions from the channels. Rb+ and Cs+ also slow clearing of Ba ions from channels. We think that (a) internally applied Ba2+ moves all the way through the channels, entering only when activation gates are open; (b) externally applied Ba2+ moves two-thirds of the way in, entering predominantly when activation gates are closed; (c) at a given voltage, Ba2+ occupies the same position in the channels whether it entered from inside or outside.

4-Aminopyridine, A Blocker of Voltage-Dependent K+ Channels, Restores Blood Pressure and Improves Survival in the Wistar Rat Model of Anaphylactic Shock

2016 ◽  
Vol 44 (11) ◽  
pp. e1082-e1089 ◽  
Author(s):  
Abdelouahab Bellou ◽  
Suleiman Al-Hammadi ◽  
Elhadi H. Aburawi ◽  
Subramanian Dhanasekaran ◽  
Abderrahim Nemmar ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Rat Model ◽  
Anaphylactic Shock ◽  
Wistar Rat ◽  
K Channels ◽  
Voltage Dependent

scholarly journals KCR1, a Membrane Protein That Facilitates Functional Expression of Non-inactivating K+Currents Associates with Rat EAG Voltage-dependent K+Channels

1998 ◽  
Vol 273 (36) ◽  
pp. 23080-23085 ◽  
Author(s):  
Naoto Hoshi ◽  
Hiroto Takahashi ◽  
Mohammad Shahidullah ◽  
Shigeru Yokoyama ◽  
Haruhiro Higashida
Keyword(s):  
Membrane Protein ◽  
Functional Expression ◽  
K Channels ◽  
Voltage Dependent ◽  
K Currents

Three distinct types of voltage-dependent K+ channels are expressed by M�ller (glial) cells of the rabbit retina

1994 ◽  
Vol 426 (1-2) ◽  
pp. 51-60 ◽  
Author(s):  
T. Ivo Chao ◽  
Andr� Henke ◽  
Winfried Reichelt ◽  
Wolfgang Eberhardt ◽  
Sigrid Reinhardt-Maelicke ◽  
...  
Keyword(s):  
Glial Cells ◽  
Rabbit Retina ◽  
K Channels ◽  
Voltage Dependent

Voltage-Dependent K Channels in Mouse Glomus Cells are Modulated by Acetylcholine

2006 ◽  
pp. 319-324 ◽  
Author(s):  
TOSHIKI OTSUBO ◽  
SHIGEKI YAMAGUCHI ◽  
MACHIKO SHIRAHATA
Keyword(s):  
K Channels ◽  
Glomus Cells ◽  
Voltage Dependent
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