Neurotransmitter-Induced Novel Modulation of a Nonselective Cation Channel by a cAMP-Dependent Mechanism in Rat Pineal Cells

1998 ◽  
Vol 79 (5) ◽  
pp. 2546-2556 ◽  
Author(s):  
Nissim Darvish ◽  
James T. Russell
Keyword(s):  
Cation Channel ◽  
Nonselective Cation Channel ◽  
Open Probability ◽  
Cell Excitability ◽  
Cation Conductance ◽  
Pituitary Adenylate Cyclase ◽  
Voltage Dependent ◽  
Inwardly Rectifying ◽  
Slow Onset ◽  
Dependent Mechanism

Darvish, Nissim and James T. Russell. Neurotransmitter-induced novel modulation of a nonselective cation channel by a cAMP-dependent mechanism in rat pineal cells. J. Neurophysiol. 79: 2546–2556, 1998. In the rat, circadian rhythm in melatonin is regulated by noradrenergic and neuropeptide inputs to the pineal via adenosine 3′,5′-cyclic monophosphate (cAMP)- and Ca2+-dependent mechanisms. We have identified a large conductance (170 pS), voltage-dependent, nonselective cation channel on rat pineal cells in culture that shows a novel mode of modulation by cAMP. Pituitary adenylate cyclase activating peptide (PACAP), norepinephrine, or 8-Br-cAMP increase channel open probability ( P o) with a hyperpolarizing shift in voltage dependence such that the channel becomes active at resting membrane potentials. The increase in P o was accompanied by a change in current rectification properties such that the channel was transformed from being inactive at rest to an inwardly rectifying cation conductance in the presence of agonist, which depolarizes the cell. This channel is calcium insensitive, is blocked by Cs+, and shows a permeability sequence: K+ > Na+ ≥ NH+ 4 > Li+. The data suggest thatPACAP and norepinephrine acting through a cAMP-dependent mechanism modulate this nonselective cation channel, resulting in a slow onset depolarization that may be important in regulation of pineal cell excitability.

ATP and calcium modulation of nonselective cation channels in IMCD cells

1994 ◽  
Vol 267 (4) ◽  
pp. F558-F565 ◽  
Author(s):  
S. Ono ◽  
T. Mougouris ◽  
T. D. DuBose ◽  
S. C. Sansom
Keyword(s):  
Cell Line ◽  
Single Channel ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Cation Channel ◽  
Bathing Solution ◽  
Nonselective Cation Channel ◽  
Open Probability ◽  
Cyclic Monophosphate ◽  
Extracellular Side

The mIMCD-3 cell line, developed from simian virus 40 transformed mice, was grown on coverslips for single-channel analysis of the apical membrane. An amiloride-sensitive nonselective cation channel (NCATP) was demonstrated that occurred predominantly in excised patches. The selectivity sequence for NCATP was NH4+ = Na+ = K+ = Li+ = Rb+ > Cl-. The single-channel conductance was 24 pS and nonrectifying in 140 mM KCl or NaCl solutions. NCATP was not permeable to barium from the extracellular side. NCATP was not voltage gated but was activated spontaneously upon patch excision or after applying negative pressure (20-40 mmHg) to an excised patch in bath solutions containing 1 microM Ca2+ [mean number of open channels (NPl) = 1.45]. NCATP was not activated when excised into a bath solution in which Ca2+ was reduced to 100 nM. The open probability of NCATP was reduced by 68% when 2 mM ATP was added to the intracellular side of an excised patch but was unaffected when 0.1 mM 8-bromoguanosine 3',5'-cyclic monophosphate was added to the intracellular side. In cell-attached patches, NCATP was activated upon response to a hyposmotic (210 mosmol/kgH2O) bathing solution containing 0.5 mM Ca2+ (NPo = 0.35). These results show that the mIMCD-3 cell line contains a volume-sensitive nonselective cation channel that is modulated by ATP and calcium but not guanosine 3',5'-cyclic monophosphate. It is postulated that NCATP may act to initiate the volume regulatory response in IMCD cells.

scholarly journals Loss of primary cilia increases polycystin-2 and TRPV4 and the appearance of a nonselective cation channel in the mouse cortical collecting duct

2019 ◽  
Vol 317 (3) ◽  
pp. F632-F637 ◽  
Author(s):  
Takamitsu Saigusa ◽  
Qiang Yue ◽  
Marlene A. Bunni ◽  
P. Darwin Bell ◽  
Douglas C. Eaton
Keyword(s):  
Collecting Duct ◽  
Cation Channel ◽  
Conditional Knockout ◽  
Nonselective Cation Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Duct Cells ◽  
Collecting Ducts ◽  
Collecting Duct Cells

Flow-related bending of cilia results in Ca2+ influx through a polycystin-1 (Pkd1) and polycystin-2 (Pkd2) complex, both of which are members of the transient receptor potential (TRP) family (TRPP1 and TRPP2, respectively). Deletion of this complex as well as cilia result in polycystic kidney disease. The Ca2+ influx pathway has been previously characterized in immortalized collecting duct cells without cilia and found to be a 23-pS channel that was a multimere of TRPP2 and TRPV4. The purpose of the present study was to determine if this TRPP2 and TRPV4 multimere exists in vivo. Apical channel activity was measured using the patch-clamp technique from isolated split-open cortical collecting ducts from adult conditional knockout mice with ( Ift88flox/flox) or without ( Ift88−/−) cilia. Single tubules were isolated for measurements of mRNA for Pkd1, Pkd2, Trpv4, and epithelial Na+ channel subunits. The predominant channel activity from Ift88flox/flox mice was from epithelial Na+ channel [5-pS Na+-selective channels with long mean open times (475.7 ± 83.26 ms) and open probability > 0.2]. With the loss of cilia, the predominant conductance was a 23-pS nonselective cation channel (reversal potential near 0) with a short mean open time (72 ± 17 ms), open probability < 0.08, and a characteristic flickery opening. Loss of cilia increased mRNA levels for Pkd2 and Trpv4 from single isolated cortical collecting ducts. In conclusion, 23-pS channels exist in vivo, and activity of this channel is elevated with loss of cilia, consistent with previous finding of an elevated-unregulated Ca2+-permeable pathway at the apical membrane of collecting duct cells that lack cilia.

Hydroxyl radical activation of a Ca2+-sensitive nonselective cation channel involved in epithelial cell necrosis

2004 ◽  
Vol 287 (4) ◽  
pp. C963-C970 ◽  
Author(s):  
Felipe Simon ◽  
Diego Varela ◽  
Ana Luisa Eguiguren ◽  
Laín F. Díaz ◽  
Francisco Sala ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Hydroxyl Radical ◽  
Cell Line ◽  
Cation Channel ◽  
Nonselective Cation Channel ◽  
Cell Necrosis ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Oxidizing Agents ◽  
Single Channel Currents

In a previous work the involvement of a fenamate-sensitive Ca2+-activated nonselective cation channel (NSCC) in free radical-induced rat liver cell necrosis was demonstrated ( 5 ). Therefore, we studied the effect of radical oxygen species and oxidizing agents on the gating behavior of a NSCC in a liver-derived epithelial cell line (HTC). Single-channel currents were recorded in HTC cells by the excised inside-out configuration of the patch-clamp technique. In this cell line, we characterize a 19-pS Ca2+-activated, ATP- and fenamate-sensitive NSCC nearly equally permeable to monovalent cations. In the presence of Fe2+, exposure of the intracellular side of NSCC to H2O2 increased their open probability ( Po) by ∼40% without affecting the unitary conductance. Desferrioxamine as well as the hydroxyl radical (·OH) scavenger MCI-186 inhibited the effect of H2O2, indicating that the increase in Po was mediated by ·OH. Exposure of the patch membrane to the oxidizing agent 5,5′-dithio- bis-2-nitrobenzoic acid (DTNB) had a similar effect to ·OH. The increase in Po induced by ·OH or DTNB was not reverted by preventing formation or by DTNB washout, respectively. However, the reducing agent dithiothreitol completely reversed the effects on Po of both ·OH and DTNB. A similar increase in Po was observed by applying the physiological oxidizing molecule GSSG. Moreover, GSSG-oxidized channels showed enhanced sensitivity to Ca2+. The effect of GSSG was fully reversed by GSH. These results suggest an intracellular site(s) of action of oxidizing agents on cysteine targets on the fenamate-sensitive NSCC protein implicated in epithelial cell necrosis.

A Na(+)-sensitive cation channel modulated by angiotensin II in cultured intestinal myocytes

1994 ◽  
Vol 266 (6) ◽  
pp. C1538-C1543 ◽  
Author(s):  
V. L. Nouailhetas ◽  
J. Aboulafia ◽  
E. Frediani-Neto ◽  
A. T. Ferreira ◽  
A. C. Paiva
Keyword(s):  
Angiotensin Ii ◽  
Guinea Pig ◽  
Cultured Cells ◽  
Single Channel ◽  
Cation Channel ◽  
Guinea Pig Ileum ◽  
Open Probability ◽  
High K ◽  
Voltage Dependent ◽  
Single Channel Currents

Single-channel currents were recorded in excised inside-out and cell-attached patches of cultured cells from the longitudinal smooth muscle of the guinea pig ileum. In the presence of symmetrical high-K+ solutions, we identified a voltage-dependent 12-pS channel. It was reversibly blocked by addition of either Ba2+ or Cs+ at the cellular side of the patch but was insensitive to Ca2+ or ATP. This channel had poor selectivity concerning cations (PLi > PK = PNa = PCa, where P is permeability) and low permeability to anions. Isosmotic substitution of NaCl for KCl in the solution facing the cellular side enhanced the channel activity by increasing NPo values where N is number of channels and Po is open probability. In the cell-attached configuration, the channel was also activated by addition of angiotensin II in the bath solution. We propose that this nonselective cation channel might play a role in the control of the membrane potential during the contractile response of the guinea pig ileum to agonists by keeping the voltage-sensitive Ca2+ channels open.

Calcium Sensitivity of a Sodium-Activated Nonselective Cation Channel in Lobster Olfactory Receptor Neurons

2003 ◽  
Vol 90 (5) ◽  
pp. 2928-2940 ◽  
Author(s):  
Yuriy V. Bobkov ◽  
Barry W. Ache
Keyword(s):  
Protein Phosphatases ◽  
Calcium Sensitivity ◽  
Cation Channel ◽  
Hill Coefficient ◽  
Nonselective Cation Channel ◽  
Open Probability ◽  
Olfactory Transduction ◽  
Phosphoinositide Signaling ◽  
A Cell ◽  
Receptor Neurons

We report that a Na+-activated nonselective cation channel described previously in lobster olfactory neurons, in which phosphoinositide signaling mediates olfactory transduction, can also be activated by Ca2+. Ca2+ activates the channel in the presence of Na+, increasing the open probability of the channel with a K1/2 of 490 nM and a Hill coefficient of 1.3. Ca2+ also increases the sensitivity of the channel to Na+. In some cells, the same channel is Ca2+ insensitive in a cell-specific manner. The nonspecific activator of protein phosphatases, protamine, applied to the intracellular face of patches containing the channel irreversibly eliminates the sensitivity to Ca2+. This effect can be blocked by okadaic acid, a nonspecific blocker of protein phosphatases, and restored by the catalytic subunit of protein kinase A in the presence of MgATP. The Ca2+-sensitive form of the channel is predominantly expressed in the transduction zone of the cells in situ. These findings imply that the Ca2+ sensitivity of the channel, and possibly its regulation by phosphorylation, play a role in olfactory transduction and help tie activation of the channel to the canonical phosphoinositide turnover pathway.

scholarly journals Kir4.1/Kir5.1 channels possess strong intrinsic inward rectification determined by a voltage-dependent K+-flux gating mechanism

2021 ◽  
Vol 153 (5) ◽  
Author(s):  
Leticia G. Marmolejo-Murillo ◽  
Iván A. Aréchiga-Figueroa ◽  
Eloy G. Moreno-Galindo ◽  
Tania Ferrer ◽  
Rodrigo Zamora-Cárdenas ◽  
...  
Keyword(s):  
Voltage Dependence ◽  
Inward Rectification ◽  
Potassium Ions ◽  
Cellular Functions ◽  
Kir Channels ◽  
Gating Mechanism ◽  
Dependent Behavior ◽  
Voltage Dependent ◽  
Inwardly Rectifying ◽  
Dependent Mechanism

Inwardly rectifying potassium (Kir) channels are broadly expressed in both excitable and nonexcitable tissues, where they contribute to a wide variety of cellular functions. Numerous studies have established that rectification of Kir channels is not an inherent property of the channel protein itself, but rather reflects strong voltage dependence of channel block by intracellular cations, such as polyamines and Mg2+. Here, we identify a previously unknown mechanism of inward rectification in Kir4.1/Kir5.1 channels in the absence of these endogenous blockers. This novel intrinsic rectification originates from the voltage-dependent behavior of Kir4.1/Kir5.1, which is generated by the flux of potassium ions through the channel pore; the inward K+-flux induces the opening of the gate, whereas the outward flux is unable to maintain the gate open. This gating mechanism powered by the K+-flux is convergent with the gating of PIP2 because, at a saturating concentration, PIP2 greatly reduces the inward rectification. Our findings provide evidence of the coexistence of two rectification mechanisms in Kir4.1/Kir5.1 channels: the classical inward rectification induced by blocking cations and an intrinsic voltage-dependent mechanism generated by the K+-flux gating.

scholarly journals Gating and Inward Rectifying Properties of the MthK K+ Channel with and without the Gating Ring

2007 ◽  
Vol 129 (2) ◽  
pp. 109-120 ◽  
Author(s):  
Yang Li ◽  
Ian Berke ◽  
Liping Chen ◽  
Youxing Jiang
Keyword(s):  
Single Channel ◽  
Hill Coefficient ◽  
K Channel ◽  
Dependent Manner ◽  
Open Probability ◽  
Ion Conduction ◽  
Voltage Dependent ◽  
Inwardly Rectifying ◽  
Kinetics Of ◽  
Gating Process

In MthK, a Ca2+-gated K+ channel from Methanobacterium thermoautotrophicum, eight cytoplasmic RCK domains form an octameric gating ring that controls the intracellular gate of the ion conduction pore. The binding of Ca2+ ions to the RCK domains alters the conformation of the gating ring, thereby opening the gate. In the present study, we examined the Ca2+- and pH-regulated gating and the rectifying conduction properties of MthK at the single-channel level. The open probability (Po) of MthK exhibits a sigmoidal relationship with intracellular [Ca2+], and a Hill coefficient &gt;1 is required to describe the dependence of Po on [Ca2+], suggesting cooperative Ca2+ activation of the channel. Additionally, intracellular Ca2+ also blocks the MthK pore in a voltage-dependent manner, rendering an apparently inwardly rectifying I-V relation. Intracellular pH has a dual effect on MthK gating. Below pH 7.5, the channel becomes insensitive to Ca2+. This occurs because the gating ring is structurally unstable at this pH and tends to disassemble (Ye, S., Y. Li, L. Chen, and Y. Jiang. 2006. Cell. 126:1161–1173). In contrast, above pH 7.5, a further increase in pH shifts the Po-[Ca2+] relation towards a lower Ca2+ concentration, augments Po at saturating [Ca2+], and activates the channel even in the absence of Ca2+. Channel activity is marked by bursts of rapid openings and closings separated by relatively longer interburst closings. The duration of interburst closing and the burst length are highly Ca2+ and pH dependent, whereas the kinetics of intraburst events is Ca2+ and pH independent. The rapid intraburst openings and closings are also observed with the isolated MthK pore lacking the attached intracellular gating ring. The fast kinetic events, independent of both Ca2+ and pH, therefore appear to be determined by processes occurring within the ion conduction pore, whereas the slow events reflect the gating process controlled by Ca2+ and pH through the gating ring.

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