Journal articles: 'Calcium activated chlorine channels'

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Hartzell, Criss, Ilva Putzier, and Jorge Arreola. "CALCIUM-ACTIVATED CHLORIDE CHANNELS." Annual Review of Physiology 67, no. 1 (March 17, 2005): 719–58. http://dx.doi.org/10.1146/annurev.physiol.67.032003.154341.

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Hao, Feng, Zhong Hai Yuan, Zhi Xin Wang, Hui Jing Xu, Fang Fang, Xin Gang Guan, Jiang Yong, and Li Yan. "Plasmid Construction of TMEM16A-pcDNA3.1 and its Application to Transient and Stable Transfection of FRT Cells." Advanced Materials Research 554-556 (July 2012): 1734–37. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.1734.

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Calcium-activated chloride channels (CaCCs) play pivotal roles in many physiological Activities, including transepithelial fluid secretion, smooth muscle contraction and sensory transduction. TMEM16A is a bona fide calcium-activated chloride channel，which was discovered by three independent labs in 2008 after Calcium-activated chloride channel current was recorded about thirty years ago. In this study, DNA fragments encoding mouse TMEM16A with green fluorescence protein (GFP) fusion protein were subcloned into pcDNA3.1/Zeo. Transient transfection condition was optimized and Fischer Thyroid epithelial cells (FRT) expressing TMEM16A were got by stable transfection. The classical calcium-activated chloride channels current was recorded in FRT cells stably expressing TMEM16A by whole cell patch clamp technique. These results were beneficial for the delving into the effects of other bivalent cations on TMEM16A-CaCCs and the role of TMEM16A-CaCCs in cell proliferation and migration.

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Hussy, N. "Calcium-activated chloride channels in cultured embryonic Xenopus spinal neurons." Journal of Neurophysiology 68, no. 6 (December 1, 1992): 2042–50. http://dx.doi.org/10.1152/jn.1992.68.6.2042.

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1. Single-channel currents were recorded from Xenopus spinal neurons developing in vitro using the patch-clamp technique, to identify the channels underlying the large and small macroscopic Ca(2+)-activated Cl- currents (ICl(Ca)) present in these cells. 2. Channels of large (maxi-channels; 310 pS) and smaller conductance (mini-channels; 50-60 pS) are activated by elevation of cytoplasmic Ca2+ concentration. Channel activity is not altered by subsequent removal of Ca2+ from the bath, arguing against a direct ligand-type Ca2+ dependence. The much higher incidence of channel activation in cell-attached patches from cells permeabilized with the Ca2+ ionophore A23187 than in excised patches also suggests the involvement of some unidentified intracellular factor. 3. The reversal potential of maxi-Cl- channels is not altered by changes in Na+ concentration, but is shifted in the negative direction by the substitution of Cl- by methanesulfonate on the intracellular side of the patch, indicating their anionic selectivity. 4. Maxi-Cl- channels exhibited the presence of multiple probable subconductance states and showed marked voltage-dependent inactivation above and below +/- 20 mV. 5. Examination of maxi-Cl- channels at early times in culture (6-9 h) and 24 h later did not reveal any developmental change in the characteristics described above. However, the mean open duration of the channel was found to increase twofold during this period of time. 6. The simultaneous presence of maxi- and mini-Cl- channels prevented detailed characterization of the latter. The anionic selectivity of mini-Cl- channels is suggested by their reversal potential that lies close to the Cl- equilibrium potential.(ABSTRACT TRUNCATED AT 250 WORDS)

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Thomas, Miracle, Mark Simms, and Prosper N’Gouemo. "Activation of Calcium-Activated Chloride Channels Suppresses Inherited Seizure Susceptibility in Genetically Epilepsy-Prone Rats." Biomedicines 10, no. 2 (February 15, 2022): 449. http://dx.doi.org/10.3390/biomedicines10020449.

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Inherited seizure susceptibility in genetically epilepsy-prone rats (GEPR-3s) is associated with increased voltage-gated calcium channel currents suggesting a massive calcium influx resulting in increased levels of intraneuronal calcium. Cytosolic calcium, in turn, activates many processes, including chloride channels, to restore normal membrane excitability and limit repetitive firing of the neurons. Here we used EACT and T16Ainh-A01, potent activator and inhibitor of calcium-activated channels transmembrane protein 16A (TMEM16A), respectively, to probe the role of these channels in the pathophysiology of acoustically evoked seizures in the GEPR-3s. We used adult male and female GEPR-3s. Acoustically evoked seizures consisted of wild running seizures (WRSs) that evolved into generalized tonic-clonic seizures (GTCSs) and eventually culminated into forelimb extension (partial tonic seizures). We found that acute EACT treatment at relatively higher tested doses significantly reduced the incidences of WRSs and GTCSs, and the seizure severity in male GEPR-3s. Furthermore, these antiseizure effects were associated with delayed seizure onset and reduced seizure duration. Interestingly, the inhibition of TMEM16A channels reversed EACT’s antiseizure effects on seizure latency and seizure duration. No notable antiseizure effects were observed in female GEPR-3s. Together, these findings suggest that activation of TMEM16A channels may represent a putative novel cellular mechanism for suppressing GTCSs.

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Yamamura, Hisao. "TMEM16 as calcium-activated chloride channels." Folia Pharmacologica Japonica 142, no. 3 (2013): 144. http://dx.doi.org/10.1254/fpj.142.144.

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Li, Weiyan, Christopher Thaler, and Paul Brehm. "Calcium Channels in Xenopus Spinal Neurons Differ in Somas and Presynaptic Terminals." Journal of Neurophysiology 86, no. 1 (July 1, 2001): 269–79. http://dx.doi.org/10.1152/jn.2001.86.1.269.

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Calcium channels play dual roles in cell signaling by promoting membrane depolarization and allowing entry of calcium ions. Patch-clamp recordings of calcium and calcium-dependent currents from the soma of Xenopus spinal neurons indicate key functional differences from those of presynaptic terminals. Both terminals and somas exhibit prominent high-voltage-activated (HVA) calcium current, but only the soma expresses additional low-voltage-activated (LVA) T-type current. Further differences are reflected in the HVA current; N- and R-type channels are predominant in the soma while the terminal calcium current is composed principally of N type with smaller contribution by L- and R-type channels. Potential physiological significance for these different distributions of channel types may lie in the differential channel kinetics. Activation of somatic HVA calcium current occurs more slowly than HVA currents in terminals. Additionally, somatic LVA calcium current activates and deactivates much more slowly than any HVA calcium current. Fast-activating and -deactivating calcium current may be critical to processing the rapid exocytotic response in terminals, whereas slow LVA and HVA calcium currents may play a central role in shaping the somatic firing pattern. In support of different kinetic behavior between these two compartments, we find that somatic calcium current activates a prominent slow chloride current not observed in terminal recordings. This current activates in response to calcium entering through either LVA or HVA channels and likely functions as a modulator of excitability or synaptic input. The restriction of this channel type to the soma lends further support to the idea that differential expression of fast and slow channel types in these neurons is dictated by differences in signaling requirements for somatic and terminal compartments.

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Dibattista, Michele, Asma Amjad, Devendra Kumar Maurya, Claudia Sagheddu, Giorgia Montani, Roberto Tirindelli, and Anna Menini. "Calcium-activated chloride channels in the apical region of mouse vomeronasal sensory neurons." Journal of General Physiology 140, no. 1 (June 25, 2012): 3–15. http://dx.doi.org/10.1085/jgp.201210780.

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The rodent vomeronasal organ plays a crucial role in several social behaviors. Detection of pheromones or other emitted signaling molecules occurs in the dendritic microvilli of vomeronasal sensory neurons, where the binding of molecules to vomeronasal receptors leads to the influx of sodium and calcium ions mainly through the transient receptor potential canonical 2 (TRPC2) channel. To investigate the physiological role played by the increase in intracellular calcium concentration in the apical region of these neurons, we produced localized, rapid, and reproducible increases in calcium concentration with flash photolysis of caged calcium and measured calcium-activated currents with the whole cell voltage-clamp technique. On average, a large inward calcium-activated current of −261 pA was measured at −50 mV, rising with a time constant of 13 ms. Ion substitution experiments showed that this current is anion selective. Moreover, the chloride channel blockers niflumic acid and 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid partially inhibited the calcium-activated current. These results directly demonstrate that a large chloride current can be activated by calcium in the apical region of mouse vomeronasal sensory neurons. Furthermore, we showed by immunohistochemistry that the calcium-activated chloride channels TMEM16A/anoctamin1 and TMEM16B/anoctamin2 are present in the apical layer of the vomeronasal epithelium, where they largely colocalize with the TRPC2 transduction channel. Immunocytochemistry on isolated vomeronasal sensory neurons showed that TMEM16A and TMEM16B coexpress in the neuronal microvilli. Therefore, we conclude that microvilli of mouse vomeronasal sensory neurons have a high density of calcium-activated chloride channels that may play an important role in vomeronasal transduction.

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Pozdnyakov, Ilya, Olga Matantseva, and Sergei Skarlato. "Consensus channelome of dinoflagellates revealed by transcriptomic analysis sheds light on their physiology." Algae 36, no. 4 (December 15, 2021): 315–26. http://dx.doi.org/10.4490/algae.2021.36.12.2.

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Ion channels are membrane protein complexes mediating passive ion flux across the cell membranes. Every organism has a certain set of ion channels that define its physiology. Dinoflagellates are ecologically important microorganisms characterized by effective physiological adaptability, which backs up their massive proliferations that often result in harmful blooms (red tides). In this study, we used a bioinformatics approach to identify homologs of known ion channels that belong to 36 ion channel families. We demonstrated that the versatility of the dinoflagellate physiology is underpinned by a high diversity of ion channels including homologs of animal and plant proteins, as well as channels unique to protists. The analysis of 27 transcriptomes allowed reconstructing a consensus ion channel repertoire (channelome) of dinoflagellates including the members of 31 ion channel families: inwardly-rectifying potassium channels, two-pore domain potassium channels, voltage-gated potassium channels (Kv), tandem Kv, cyclic nucleotide-binding domain-containing channels (CNBD), tandem CNBD, eukaryotic ionotropic glutamate receptors, large-conductance calcium-activated potassium channels, intermediate/small-conductance calcium-activated potassium channels, eukaryotic single-domain voltage-gated cation channels, transient receptor potential channels, two-pore domain calcium channels, four-domain voltage-gated cation channels, cation and anion Cys-loop receptors, small-conductivity mechanosensitive channels, large-conductivity mechanosensitive channels, voltage-gated proton channels, inositole-1,4,5- trisphosphate receptors, slow anion channels, aluminum-activated malate transporters and quick anion channels, mitochondrial calcium uniporters, voltage-dependent anion channels, vesicular chloride channels, ionotropic purinergic receptors, animal volage-insensitive cation channels, channelrhodopsins, bestrophins, voltage-gated chloride channels H+/Cl- exchangers, plant calcium-permeable mechanosensitive channels, and trimeric intracellular cation channels. Overall, dinoflagellates represent cells able to respond to physical and chemical stimuli utilizing a wide range of Gprotein coupled receptors- and Ca2+-dependent signaling pathways. The applied approach not only shed light on the ion channel set in dinoflagellates, but also provided the information on possible molecular mechanisms underlying vital cellular processes dependent on the ion transport.

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Kaneko, Hiroshi, Frank Möhrlen, and Stephan Frings. "Calmodulin Contributes to Gating Control in Olfactory Calcium-activated Chloride Channels." Journal of General Physiology 127, no. 6 (May 30, 2006): 737–48. http://dx.doi.org/10.1085/jgp.200609497.

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In sensory neurons of the peripheral nervous system, receptor potentials can be amplified by depolarizing Cl currents. In mammalian olfactory sensory neurons (OSNs), this anion-based signal amplification results from the sequential activation of two distinct types of transduction channels: cAMP-gated Ca channels and Ca-activated Cl channels. The Cl current increases the initial receptor current about 10-fold and leads to the excitation of the neuron. Here we examine the activation mechanism of the Ca-dependent Cl channel. We focus on calmodulin, which is known to mediate Ca effects on various ion channels. We show that the cell line Odora, which is derived from OSN precursor cells in the rat olfactory epithelium, expresses Ca-activated Cl channels. Single-channel conductance, ion selectivity, voltage dependence, sensitivity to niflumic acid, and Ca sensitivity match between Odora channels and OSN channels. Transfection of Odora cells with CaM mutants reduces the Ca sensitivity of the Cl channels. This result points to the participation of calmodulin in the gating process of Ca-ativated Cl channels, and helps to understand how signal amplification works in the olfactory sensory cilia. Calmodulin was previously shown to mediate feedback inhibition of cAMP-synthesis and of the cAMP-gated Ca channels in OSNs. Our results suggest that calmodulin may also be instrumental in the generation of the excitatory Cl current. It appears to play a pivotal role in the peripheral signal processing of olfactory sensory information. Moreover, recent results from other peripheral neurons, as well as from smooth muscle cells, indicate that the calmodulin-controlled, anion-based signal amplification operates in various cell types where it converts Ca signals into membrane depolarization.

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10

Lalonde, Melanie, Melanie Kelly, and Steven Barnes. "Calcium-activated chloride channels in the retina." Channels 2, no. 4 (July 4, 2008): 252–60. http://dx.doi.org/10.4161/chan.2.4.6704.

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11

Kolesnikov, Dmitrii, Anastasiia Perevoznikova, Konstantin Gusev, Lyubov Glushankova, Elena Kaznacheyeva, and Alexey Shalygin. "Electrophysiological Properties of Endogenous Single Ca2+ Activated Cl− Channels Induced by Local Ca2+ Entry in HEK293." International Journal of Molecular Sciences 22, no. 9 (April 30, 2021): 4767. http://dx.doi.org/10.3390/ijms22094767.

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Microdomains formed by proteins of endoplasmic reticulum and plasma membrane play a key role in store-operated Ca2+ entry (SOCE). Ca2+ release through inositol 1,4,5-trisphosphate receptor (IP3R) and subsequent Ca2+ store depletion activate STIM (stromal interaction molecules) proteins, sensors of intraluminal Ca2+, which, in turn, open the Orai channels in plasma membrane. Downstream to this process could be activated TRPC (transient receptor potential-canonical) calcium permeable channels. Using single channel patch-clamp technique we found that a local Ca2+ entry through TRPC1 channels activated endogenous Ca2+-activated chloride channels (CaCCs) with properties similar to Anoctamin6 (TMEM16F). Our data suggest that their outward rectification is based on the dependence from membrane potential of both the channel conductance and the channel activity: (1) The conductance of active CaCCs highly depends on the transmembrane potential (from 3 pS at negative potentials till 60 pS at positive potentials); (2) their activity (NPo) is enhanced with increasing Ca2+ concentration and/or transmembrane potential, conversely lowering of intracellular Ca2+ concentration reduced the open state dwell time; (3) CaCC amplitude is only slightly increased by intracellular Ca2+ concentration. Experiments with Ca2+ buffering by EGTA or BAPTA suggest close local arrangement of functional CaCCs and TRPC1 channels. It is supposed that Ca2+-activated chloride channels are involved in Ca2+ entry microdomains.

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12

Gomez-Hernandez, Juan-Manuel, Walter Stühmer, and Anant B. Parekh. "Calcium dependence and distribution of calcium-activated chloride channels inXenopusoocytes." Journal of Physiology 502, no. 3 (August 1997): 569–74. http://dx.doi.org/10.1111/j.1469-7793.1997.569bj.x.

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13

Kourie, J. I., D. R. Laver, G. P. Ahern, and A. F. Dulhunty. "A calcium-activated chloride channel in sarcoplasmic reticulum vesicles from rabbit skeletal muscle." American Journal of Physiology-Cell Physiology 270, no. 6 (June 1, 1996): C1675—C1686. http://dx.doi.org/10.1152/ajpcell.1996.270.6.c1675.

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A Ca(2+)-activated Cl- channel is described in sarcoplasmic reticulum (SR) enriched vesicles of skeletal muscle incorporated into lipid bilayers. Small chloride (SCl) channels (n = 20) were rapidly and reversibly activated when cis- (cytoplasmic) [Ca2+] was increased above 10(-7) M, with trans-(luminal) [Ca2+] at either 10(-3) or 10(-7) M. The open probability of single channels increased from zero when cis-[Ca2+] was 10(-7) M to 0.61 +/- 0.12 when [Ca2+] was 10(-4) M. High- and low-conductance levels in single-channel activity were activated at different cis-[Ca2+]. Channel openings to the maximum conductance, 65-75 pS (250/50 mM Cl-, cis/ trans), were active when cis-[Ca2+] was increased above 5 x 10(-6) M. In contrast to the maximum conductance, channel openings to submaximal levels between 5 and 40 pS were activated at a lower cis-[Ca2+] and dominated channel activity between 5 x 10(-7) and 5 x 10(-6) M. Activation of SCl channels was Ca2+ specific and not reproduced by cytoplasmic Mg2+ concentrations of 10(-3) M. We suggest that the SCl channel arises in the SR membrane. The Ca2+ dependence of this channel implies that it is active at [Ca2+] achieved during muscle contraction.

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Tang, Xiang D., Heather Daggett, Markus Hanner, Maria L. Garcia, Owen B. McManus, Nathan Brot, Herbert Weissbach, Stefan H. Heinemann, and Toshinori Hoshi. "Oxidative Regulation of Large Conductance Calcium-Activated Potassium Channels." Journal of General Physiology 117, no. 3 (February 26, 2001): 253–74. http://dx.doi.org/10.1085/jgp.117.3.253.

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Reactive oxygen/nitrogen species are readily generated in vivo, playing roles in many physiological and pathological conditions, such as Alzheimer's disease and Parkinson's disease, by oxidatively modifying various proteins. Previous studies indicate that large conductance Ca2+-activated K+ channels (BKCa or Slo) are subject to redox regulation. However, conflicting results exist whether oxidation increases or decreases the channel activity. We used chloramine-T, which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation in the cloned human Slo (hSlo) channel expressed in mammalian cells. In the virtual absence of Ca2+, the oxidant shifted the steady-state macroscopic conductance to a more negative direction and slowed deactivation. The results obtained suggest that oxidation enhances specific voltage-dependent opening transitions and slows the rate-limiting closing transition. Enhancement of the hSlo activity was partially reversed by the enzyme peptide methionine sulfoxide reductase, suggesting that the upregulation is mediated by methionine oxidation. In contrast, hydrogen peroxide and cysteine-specific reagents, DTNB, MTSEA, and PCMB, decreased the channel activity. Chloramine-T was much less effective when concurrently applied with the K+ channel blocker TEA, which is consistent with the possibility that the target methionine lies within the channel pore. Regulation of the Slo channel by methionine oxidation may represent an important link between cellular electrical excitability and metabolism.

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Eggermont, J. "Calcium-activated Chloride Channels: (Un)known, (Un)loved?" Proceedings of the American Thoracic Society 1, no. 1 (January 1, 2004): 22–27. http://dx.doi.org/10.1513/pats.2306010.

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Kurtz, A. "Do Calcium-Activated Chloride Channels Control Renin Secretion?" Physiology 5, no. 2 (April 1, 1990): 43–46. http://dx.doi.org/10.1152/physiologyonline.1990.5.2.43.

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The rate of renin secretion from renal juxtaglomerular epithelioid cells appears to be inversely correlated to intracellular Ca activity. Such a dependency of renin secretion on Ca activity could be controlled by Ca-activated Cl channels that may be involved in the volume control of juxtaglomerular cells.

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Kuan, Ai-Seon, Yu-Li Ni, and Tsung-Yu Chen. "Electrophysiological Properties of TMEM16A Calcium-Activated Chloride Channels." Biophysical Journal 106, no. 2 (January 2014): 145a. http://dx.doi.org/10.1016/j.bpj.2013.11.838.

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18

Mercer, A. J., K. Rabl, G. E. Riccardi, N. C. Brecha, S. L. Stella, and W. B. Thoreson. "Location of Release Sites and Calcium-Activated Chloride Channels Relative to Calcium Channels at the Photoreceptor Ribbon Synapse." Journal of Neurophysiology 105, no. 1 (January 2011): 321–35. http://dx.doi.org/10.1152/jn.00332.2010.

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Vesicle release from photoreceptor ribbon synapses is regulated by L-type Ca2+ channels, which are in turn regulated by Cl− moving through calcium-activated chloride [Cl(Ca)] channels. We assessed the proximity of Ca2+ channels to release sites and Cl(Ca) channels in synaptic terminals of salamander photoreceptors by comparing fast (BAPTA) and slow (EGTA) intracellular Ca2+ buffers. BAPTA did not fully block synaptic release, indicating some release sites are <100 nm from Ca2+ channels. Comparing Cl(Ca) currents with predicted Ca2+ diffusion profiles suggested that Cl(Ca) and Ca2+ channels average a few hundred nanometers apart, but the inability of BAPTA to block Cl(Ca) currents completely suggested some channels are much closer together. Diffuse immunolabeling of terminals with an antibody to the putative Cl(Ca) channel TMEM16A supports the idea that Cl(Ca) channels are dispersed throughout the presynaptic terminal, in contrast with clustering of Ca2+ channels near ribbons. Cl(Ca) currents evoked by intracellular calcium ion concentration ([Ca2+]i) elevation through flash photolysis of DM-nitrophen exhibited EC50 values of 556 and 377 nM with Hill slopes of 1.8 and 2.4 in rods and cones, respectively. These relationships were used to estimate average submembrane [Ca2+]i in photoreceptor terminals. Consistent with control of exocytosis by [Ca2+] nanodomains near Ca2+ channels, average submembrane [Ca2+]i remained below the vesicle release threshold (∼400 nM) over much of the physiological voltage range for cones. Positioning Ca2+ channels near release sites may improve fidelity in converting voltage changes to synaptic release. A diffuse distribution of Cl(Ca) channels may allow Ca2+ influx at one site to influence relatively distant Ca2+ channels.

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Ackerman, M. J., K. D. Wickman, and D. E. Clapham. "Hypotonicity activates a native chloride current in Xenopus oocytes." Journal of General Physiology 103, no. 2 (February 1, 1994): 153–79. http://dx.doi.org/10.1085/jgp.103.2.153.

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Xenopus oocytes are frequently utilized for in vivo expression of cellular proteins, especially ion channel proteins. A thorough understanding of the endogenous conductances and their regulation is paramount for proper characterization of expressed channel proteins. Here we detail a novel chloride current (ICl.swell) responsive to hypotonicity in Xenopus oocytes using the two-electrode voltage clamp technique. Reducing the extracellular osmolarity by 50% elicited a calcium-independent chloride current having an anion conductivity sequence identical with swelling-induced chloride currents observed in epithelial cells. The hypotonicity-activated current was blocked by chloride channel blockers, trivalent lanthanides, and nucleotides. G-protein, cAMP-PKA, and arachidonic acid signaling cascades were not involved in ICl.swell activation. ICl.swell is distinct from both stretch-activated nonselective cation channels and the calcium-activated chloride current in oocytes and may play a critical role in volume regulation in Xenopus oocytes.

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20

Mangel, A. W., L. Scott, and R. A. Liddle. "Depolarization-stimulated cholecystokinin secretion is mediated by L-type calcium channels in STC-1 cells." American Journal of Physiology-Gastrointestinal and Liver Physiology 270, no. 2 (February 1, 1996): G287—G290. http://dx.doi.org/10.1152/ajpgi.1996.270.2.g287.

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To examine the role of calcium channels in depolarization-activated cholecystokinin (CCK) release, studies were performed in an intestinal CCK-secreting cell line, STC-1. Blockade of potassium channels with barium chloride (5 mM) increased the release of CCK by 374.6 +/- 46.6% of control levels. Barium-induced secretion was inhibited by the L-type calcium-channel blocker, nicardipine. Nicardipine (10(-9)-10(-5) M) produced a dose-dependent inhibition in barium-stimulated secretion with a half-maximal inhibition (IC50) value of 0.1 microM. A second L-type calcium-channel blocker, diltiazem (10(-9)-10(-4) M), also inhibited barium-induced CCK secretion with an IC50 value of 5.1 microM. By contrast, the T-type calcium-channel blocker, nickel chloride (10(-7)-10(-8) M), failed to significantly inhibit barium-induced CCK secretion. To further evaluate a role for L-type calcium channels in the secretion of CCK, the effects of the L-type calcium channel opener, BAY K 8644, were examined. BAY K 8644 (10(-8)-10(-4) M) produced a dose-dependent stimulation in CCK release with a mean effective concentration value of 0.2 microM. Recordings of single-channel currents from inside-out membrane patches showed activation of calcium channels by BAY K 8644 (1 microM), with a primary channel conductance of 26.0 +/- 1.2 pS. It is concluded that inhibition of potassium channel activity depolarizes the plasma membrane, thereby activating L-type, but not T-type, calcium channels. The corresponding influx of calcium serves to trigger secretion of CCK.

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Jensen, B. L., P. Ellekvist, and O. Skott. "Chloride is essential for contraction of afferent arterioles after agonists and potassium." American Journal of Physiology-Renal Physiology 272, no. 3 (March 1, 1997): F389—F396. http://dx.doi.org/10.1152/ajprenal.1997.272.3.f389.

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A depolarizing chloride efflux has been suggested to activate voltage-dependent calcium channels in renal afferent arteriolar smooth muscle cells in response to vasoconstrictors. To test this proposal, rabbit afferent arterioles were microperfused, and the contractile dose responses to norepinephrine, angiotensin II (ANG II), and potassium were measured after chloride depletion and compared with controls. Chloride depletion did not change arteriolar diameters, but the response to norepinephrine was markedly reduced when chloride was substituted with gluconate (n = 6) or isethionate (n = 6). Reintroduction of chloride fully restored the sensitivity to norepinephrine. Contractions after ANG II and potassium were totally abolished in the absence of chloride (n = 6). In additional experiments (n = 7), the arteriolar contraction to 100 mM potassium was abolished only 1 min after removal of extracellular chloride. We conclude that norepinephrine and ANG II use different mechanisms for contraction and that extracellular chloride is essential for contraction in afferent arterioles after activation of voltage-dependent calcium channels. We suggest that a chloride influx pathway is activated concomitantly with the voltage-dependent calcium channel to allow chloride influx to compensate for the cation influx.

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Elorza-Vidal, Xabier, Héctor Gaitán-Peñas, and Raúl Estévez. "Chloride Channels in Astrocytes: Structure, Roles in Brain Homeostasis and Implications in Disease." International Journal of Molecular Sciences 20, no. 5 (February 27, 2019): 1034. http://dx.doi.org/10.3390/ijms20051034.

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Astrocytes are the most abundant cell type in the CNS (central nervous system). They exert multiple functions during development and in the adult CNS that are essential for brain homeostasis. Both cation and anion channel activities have been identified in astrocytes and it is believed that they play key roles in astrocyte function. Whereas the proteins and the physiological roles assigned to cation channels are becoming very clear, the study of astrocytic chloride channels is in its early stages. In recent years, we have moved from the identification of chloride channel activities present in astrocyte primary culture to the identification of the proteins involved in these activities, the determination of their 3D structure and attempts to gain insights about their physiological role. Here, we review the recent findings related to the main chloride channels identified in astrocytes: the voltage-dependent ClC-2, the calcium-activated bestrophin, the volume-activated VRAC (volume-regulated anion channel) and the stress-activated Maxi-Cl−. We discuss key aspects of channel biophysics and structure with a focus on their role in glial physiology and human disease.

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Zamoyski, V. L., E. V. Bovina, and V. V. Grigoriev. "Properties of Calcium-Activated Chloride Currents in Rat Purkinje Cerebellum Neurons." Biomedical Chemistry: Research and Methods 1, no. 3 (2018): e00034. http://dx.doi.org/10.18097/bmcrm00034.

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The presence of calcium-activated chloride current was shown using on freshly isolated rat Purkinje cerebellum neiurones and the pacth-clamp method in the whole-cell configuration. Chloride currents appeared in sodium-free external solution and reversibly disappeared in chloride-free or calcium-free external solution. Replacing of K+ ions (120 mM) to Cs+ ions in micropipette (120 mM) show the chloride currents even with 140 mM Na+ in external solution. This current was blocked to 80–100% by nifluminic acid (25–100 ΜM). It was found out that well known blockers of potassium channels tetraethylammonium (TEA) and 4-aminopyridine (4-AP) also effectively blocked chloride channels. The IC50 values for TEA and 4-AP were 130 ΜM, and 110 ΜM respectively. The action of TEA was reversible, while 4-AP at concentration 100 ΜM and above irreversibly blocked chloride channels.

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Forrest, Abigail S., Talia C. Joyce, Marissa L. Huebner, Ramon J. Ayon, Michael Wiwchar, John Joyce, Natalie Freitas, et al. "Increased TMEM16A-encoded calcium-activated chloride channel activity is associated with pulmonary hypertension." American Journal of Physiology-Cell Physiology 303, no. 12 (December 15, 2012): C1229—C1243. http://dx.doi.org/10.1152/ajpcell.00044.2012.

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Pulmonary artery smooth muscle cells (PASMCs) are more depolarized and display higher Ca2+ levels in pulmonary hypertension (PH). Whether the functional properties and expression of Ca2+-activated Cl− channels (ClCa), an important excitatory mechanism in PASMCs, are altered in PH is unknown. The potential role of ClCa channels in PH was investigated using the monocrotaline (MCT)-induced PH model in the rat. Three weeks postinjection with a single dose of MCT (50 mg/kg ip), the animals developed right ventricular hypertrophy (heart weight measurements) and changes in pulmonary arterial flow (pulse-waved Doppler imaging) that were consistent with increased pulmonary arterial pressure and PH. Whole cell patch experiments revealed an increase in niflumic acid (NFA)-sensitive Ca2+-activated Cl− current [ ICl(Ca)] density in PASMCs from large conduit and small intralobar pulmonary arteries of MCT-treated rats vs. aged-matched saline-injected controls. Quantitative RT-PCR and Western blot analysis revealed that the alterations in ICl(Ca) were accompanied by parallel changes in the expression of TMEM16A, a gene recently shown to encode for ClCa channels. The contraction to serotonin of conduit and intralobar pulmonary arteries from MCT-treated rats exhibited greater sensitivity to nifedipine (1 μM), an l-type Ca2+ channel blocker, and NFA (30 or 100 μM, with or without 10 μM indomethacin to inhibit cyclooxygenases) or T16AInh-A01 (10 μM), TMEM16A/ClCa channel inhibitors, than that of control animals. In conclusion, augmented ClCa/TMEM16A channel activity is a major contributor to the changes in electromechanical coupling of PA in this model of PH. TMEM16A-encoded channels may therefore represent a novel therapeutic target in this disease.

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Flores, C. A., L. P. Cid, F. V. Sepúlveda, and M. I. Niemeyer. "TMEM16 proteins: the long awaited calcium-activated chloride channels?" Brazilian Journal of Medical and Biological Research 42, no. 11 (September 25, 2009): 993–1001. http://dx.doi.org/10.1590/s0100-879x2009005000028.

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Pifferi, Simone. "Permeation Mechanisms in the TMEM16B Calcium-Activated Chloride Channels." PLOS ONE 12, no. 1 (January 3, 2017): e0169572. http://dx.doi.org/10.1371/journal.pone.0169572.

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Ni, Yu-Li, Ai-Seon Kuan, and Tsung-Yu Chen. "Activation and Inhibition of TMEM16A Calcium-Activated Chloride Channels." PLoS ONE 9, no. 1 (January 29, 2014): e86734. http://dx.doi.org/10.1371/journal.pone.0086734.

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Salzer, Isabella, and Stefan Boehm. "Calcium-activated chloride channels: Potential targets for antinociceptive therapy." International Journal of Biochemistry & Cell Biology 111 (June 2019): 37–41. http://dx.doi.org/10.1016/j.biocel.2019.04.006.

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Hoffmann, Else Kay, Niels Bjerre Holm, and Ian Henry Lambert. "Functions of volume-sensitive and calcium-activated chloride channels." IUBMB Life 66, no. 4 (April 2014): 257–67. http://dx.doi.org/10.1002/iub.1266.

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Jeng, Grace, Muskaan Aggarwal, Wei-Ping Yu, and Tsung-Yu Chen. "Activating Individual Subunits of TMEM16A Calcium-Activated Chloride Channels." Biophysical Journal 110, no. 3 (February 2016): 290a—291a. http://dx.doi.org/10.1016/j.bpj.2015.11.1571.

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Kuruma, Akinori, and H. Criss Hartzell. "Dynamics of calcium regulation of chloride currents inXenopus oocytes." American Journal of Physiology-Cell Physiology 276, no. 1 (January 1, 1999): C161—C175. http://dx.doi.org/10.1152/ajpcell.1999.276.1.c161.

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Ca-activated Cl currents are widely expressed in many cell types and play diverse and important physiological roles. The Xenopus oocyte is a good model system for studying the regulation of these currents. We previously showed that inositol 1,4,5-trisphosphate (IP3) injection into Xenopus oocytes rapidly elicits a noninactivating outward Cl current ( I Cl1-S) followed several minutes later by the development of slow inward ( I Cl2) and transient outward ( I Cl1-T) Cl currents. In this paper, we investigate whether these three currents are mediated by the same or different Cl channels. Outward Cl currents were more sensitive to Ca than inward Cl currents, as shown by injection of different amounts of Ca or by Ca influx through a heterologously expressed ligand-gated Ca channel, the ionotropic glutamate receptor iGluR3. These data could be explained by two channels with different Ca affinities or one channel with a higher Ca affinity at depolarized potentials. To distinguish between these possibilities, we determined the anion selectivity of the three currents. The anion selectivity sequences for the three currents were the same (I > Br > Cl), but I Cl1-Shad an I-to-Cl permeability ratio more than twofold smaller than the other two currents. The different anion selectivities and instantaneous current-voltage relationships were consistent with at least two different channels mediating these currents. However, after consideration of possible errors, the hypothesis that a single type of Cl channel underlies the complex waveforms of the three different macroscopic Ca-activated Cl currents in Xenopus oocytes remains a viable alternative.

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Jan, Lily. "Contribution of Potassium Channels and Calcium-Activated Chloride Channels to Neuronal Signaling." Biophysical Journal 104, no. 2 (January 2013): 196a. http://dx.doi.org/10.1016/j.bpj.2012.11.1104.

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Hao, Feng, Yi Ju Hou, Chen Zhao, Li Zhang, Zhi Qiang Tong, Ai Tong Li, Bo Yi, et al. "Expression Clone of TMEM16A as a Calcium-Activated Chloride Channels in CHO Cells." Advanced Materials Research 709 (June 2013): 832–35. http://dx.doi.org/10.4028/www.scientific.net/amr.709.832.

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There is compelling evidence that TMEM16A fuctions as calcium-activated chloride channels (CaCCS), which was discovered by three independent labs in 2008 after Calcium-activated chloride channel current was first recorded in the 1980s. CaCCs are involved in many physiological processes, including transepithelial fluid secretion, smooth muscle contraction , sensory signal transduction and others. CaCCs are considers as potential drug therapy of hypertension, secretoy diarrheas, neuropathic pain, asthma, cystic fibrosis and certain tumors. In our previous study, TMEM16A with green fluorescence protein (GFP) fusion protein were subcloned into pcDNA3.1/Zeo. In this study, TMEM16A transient transfection conditon of Chinese hamster ovary (CHO) cells were optimized through liposome transfection and CHO cells expressing TMEM16A were got by stable transfection in which the classical calcium-activated chloride channels current was recorded by whole cell patch clamp technique. By a comparison between the results in this study and the results in previous study, both CHO and FRT cells are suitable for TMEM16A-pcDNA3.1 expression through liposome transfection and currents were recorded in both FRT and CHO cells by whole cell patch clamp technique, but our results indicated different purposes should require different cell lines and methods. These results were beneficial for the delving into study of TMEM16A-CaCCs by patch clamp technique which is the gold standard for real-time investigation of ion channels and their effectors.

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KOTLIKOFF, MICHAEL I, and YONG-XIAO WANG. "Calcium Release and Calcium-Activated Chloride Channels in Airway Smooth Muscle Cells." American Journal of Respiratory and Critical Care Medicine 158, supplement_2 (November 1998): S109—S114. http://dx.doi.org/10.1164/ajrccm.158.supplement_2.13tac600.

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Vocke, Kerstin, Kristin Dauner, Anne Hahn, Anne Ulbrich, Jana Broecker, Sandro Keller, Stephan Frings, and Frank Möhrlen. "Calmodulin-dependent activation and inactivation of anoctamin calcium-gated chloride channels." Journal of General Physiology 142, no. 4 (September 30, 2013): 381–404. http://dx.doi.org/10.1085/jgp.201311015.

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Calcium-dependent chloride channels serve critical functions in diverse biological systems. Driven by cellular calcium signals, the channels codetermine excitatory processes and promote solute transport. The anoctamin (ANO) family of membrane proteins encodes three calcium-activated chloride channels, named ANO 1 (also TMEM16A), ANO 2 (also TMEM16B), and ANO 6 (also TMEM16F). Here we examined how ANO 1 and ANO 2 interact with Ca2+/calmodulin using nonstationary current analysis during channel activation. We identified a putative calmodulin-binding domain in the N-terminal region of the channel proteins that is involved in channel activation. Binding studies with peptides indicated that this domain, a regulatory calmodulin-binding motif (RCBM), provides two distinct modes of interaction with Ca2+/calmodulin, one at submicromolar Ca2+ concentrations and one in the micromolar Ca2+ range. Functional, structural, and pharmacological data support the concept that calmodulin serves as a calcium sensor that is stably associated with the RCBM domain and regulates the activation of ANO 1 and ANO 2 channels. Moreover, the predominant splice variant of ANO 2 in the brain exhibits Ca2+/calmodulin-dependent inactivation, a loss of channel activity within 30 s. This property may curtail ANO 2 activity during persistent Ca2+ signals in neurons. Mutagenesis data indicated that the RCBM domain is also involved in ANO 2 inactivation, and that inactivation is suppressed in the retinal ANO 2 splice variant. These results advance the understanding of Ca2+ regulation in anoctamin Cl− channels and its significance for the physiological function that anoctamin channels subserve in neurons and other cell types.

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Xu, Yanfang, Pei Hong Dong, Zhao Zhang, Gias Uddin Ahmmed, and Nipavan Chiamvimonvat. "Presence of a calcium-activated chloride current in mouse ventricular myocytes." American Journal of Physiology-Heart and Circulatory Physiology 283, no. 1 (July 1, 2002): H302—H314. http://dx.doi.org/10.1152/ajpheart.00044.2002.

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The properties of several components of outward K+ currents, including the pharmacological and kinetics profiles as well as the respective molecular correlates, have been identified in mouse cardiac myocytes. Surprisingly little is known with regard to the Ca2+-activated ionic currents. We studied the Ca2+-activated transient outward currents in mouse ventricular myocytes. We have identified a 4-aminopyridine (4-AP)- and tetraethyl ammonium-resistant transient outward current that is Ca2+ dependent. The current is carried by Cl−and is critically dependent on Ca2+ influx via voltage-gated Ca2+ channels and the sarcoplasmic reticulum Ca2+ store. The current can be blocked by the anion transport blockers niflumic acid and 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid. Single channel recordings reveal small conductance channels (∼1 pS in 140 mM Cl−) that can be blocked by anion transport blockers. Ensemble-averaged current faithfully mirrors the transient kinetics observed at the whole level. Niflumic acid (in the presence of 4-AP) leads to prolongation of the early repolarization. Thus this current may contribute to early repolarization of action potentials in mouse ventricular myocytes.

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Richards, N. W., R. J. Lowy, S. A. Ernst, and D. C. Dawson. "Two K+ channel types, muscarinic agonist-activated and inwardly rectifying, in a Cl- secretory epithelium: the avian salt gland." Journal of General Physiology 93, no. 6 (June 1, 1989): 1171–94. http://dx.doi.org/10.1085/jgp.93.6.1171.

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Patches of membrane on cells isolated from the nasal salt gland of the domestic duck typically contained two types of K+ channel. One was a large-conductance ("maxi") K+ channel which was activated by intracellular calcium and/or depolarizing membrane voltages, and the other was a smaller-conductance K+ channel which exhibited at least two conductance levels and displayed pronounced inward rectification. Barium blocked both channels, but tetraethylammonium chloride and quinidine selectively blocked the larger K+ channel. The large K+ channel did not appear to open under resting conditions but could be activated by application of the muscarinic agonist, carbachol. The smaller channels were open under resting conditions but the gating was not affected by carbachol. Both of these channels reside in the basolateral membranes of the Cl- secretory cells but they appear to play different roles in the life of the cell.

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Amjad, Asma, Andres Hernandez-Clavijo, Simone Pifferi, Devendra Kumar Maurya, Anna Boccaccio, Jessica Franzot, Jason Rock, and Anna Menini. "Conditional knockout of TMEM16A/anoctamin1 abolishes the calcium-activated chloride current in mouse vomeronasal sensory neurons." Journal of General Physiology 145, no. 4 (March 16, 2015): 285–301. http://dx.doi.org/10.1085/jgp.201411348.

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Pheromones are substances released from animals that, when detected by the vomeronasal organ of other individuals of the same species, affect their physiology and behavior. Pheromone binding to receptors on microvilli on the dendritic knobs of vomeronasal sensory neurons activates a second messenger cascade to produce an increase in intracellular Ca2+ concentration. Here, we used whole-cell and inside-out patch-clamp analysis to provide a functional characterization of currents activated by Ca2+ in isolated mouse vomeronasal sensory neurons in the absence of intracellular K+. In whole-cell recordings, the average current in 1.5 µM Ca2+ and symmetrical Cl− was −382 pA at −100 mV. Ion substitution experiments and partial blockade by commonly used Cl− channel blockers indicated that Ca2+ activates mainly anionic currents in these neurons. Recordings from inside-out patches from dendritic knobs of mouse vomeronasal sensory neurons confirmed the presence of Ca2+-activated Cl− channels in the knobs and/or microvilli. We compared the electrophysiological properties of the native currents with those mediated by heterologously expressed TMEM16A/anoctamin1 or TMEM16B/anoctamin2 Ca2+-activated Cl− channels, which are coexpressed in microvilli of mouse vomeronasal sensory neurons, and found a closer resemblance to those of TMEM16A. We used the Cre–loxP system to selectively knock out TMEM16A in cells expressing the olfactory marker protein, which is found in mature vomeronasal sensory neurons. Immunohistochemistry confirmed the specific ablation of TMEM16A in vomeronasal neurons. Ca2+-activated currents were abolished in vomeronasal sensory neurons of TMEM16A conditional knockout mice, demonstrating that TMEM16A is an essential component of Ca2+-activated Cl− currents in mouse vomeronasal sensory neurons.

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Koumi, S., R. Sato, and T. Aramaki. "Characterization of the calcium-activated chloride channel in isolated guinea-pig hepatocytes." Journal of General Physiology 104, no. 2 (August 1, 1994): 357–73. http://dx.doi.org/10.1085/jgp.104.2.357.

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Macroscopic and unitary currents through Ca(2+)-activated Cl- channels were examined in enzymatically isolated guinea-pig hepatocytes using whole-cell, excised outside-out and inside-out configurations of the patch-clamp technique. When K+ conductances were blocked and the intracellular Ca2+ concentration ([Ca2+]i) was set at 1 microM (pCa = 6), membrane currents were observed under whole-cell voltage-clamp conditions. The reversal potential of the current shifted by approximately 60 mV per 10-fold change in the external Cl- concentration. In addition, the current did not appear when Cl- was omitted from the internal and external solutions, indicating that the current was Cl- selective. The current was activated by increasing [Ca2+]i and was inactivated in Ca(2+)-free, 5 mM EGTA internal solution (pCa > 9). The current was inhibited by bath application of 9-anthracenecarboxylic acid (9-AC) and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) in a voltage-dependent manner. In single channel recordings from outside-out patches, unitary current activity was observed, whose averaged slope conductance was 7.4 +/- 0.5 pS (n = 18). The single channel activity responded to extracellular Cl- changes as expected for a Cl- channel current. The open time distribution was best described by a single exponential function with mean open lifetime of 97.6 +/- 10.4 ms (n = 11), while at least two exponentials were required to fit the closed time distributions with a time constant for the fast component of 21.5 +/- 2.8 ms (n = 11) and that for the slow component of 411.9 +/- 52.0 ms (n = 11). In excised inside-out patch recordings, channel open probability was sensitive to [Ca2+]i. The relationship between [Ca2+]i and channel activity was fitted by the Hill equation with a Hill coefficient of 3.4 and the half-maximal activation was 0.48 microM. These results suggest that guinea-pig hepatocytes possess Ca(2+)-activated Cl- channels.

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Leblanc, Normand, Jonathan Ledoux, Sohag Saleh, Amy Sanguinetti, Jeff Angermann, Kate O'Driscoll, Fiona Britton, Brian A. Perrino, and Iain A. Greenwood. "Regulation of calcium-activated chloride channels in smooth muscle cells: a complex picture is emerging." Canadian Journal of Physiology and Pharmacology 83, no. 7 (July 1, 2005): 541–56. http://dx.doi.org/10.1139/y05-040.

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Calcium-activated chloride channels (ClCa) are ligand-gated anion channels as they have been shown to be activated by a rise in intracellular Ca2+ concentration in various cell types including cardiac, skeletal and vascular smooth muscle cells, endothelial and epithelial cells, as well as neurons. Because ClCa channels are normally closed at resting, free intracellular Ca2+ concentration (~100 nmol/L) in most cell types, they have generally been considered excitatory in nature, providing a triggering mechanism during signal transduction for membrane excitability, osmotic balance, transepithelial chloride movements, or fluid secretion. Unfortunately, the genes responsible for encoding this class of ion channels is still unknown. This review centers primarily on recent findings on the properties of these channels in smooth muscle cells. The first section discusses the functional significance and biophysical and pharmacological properties of ClCa channels in smooth muscle cells, and ends with a description of 2 candidate gene families (i.e., CLCA and Bestrophin) that are postulated to encode for these channels in various cell types. The second section provides a summary of recent findings demonstrating the regulation of native ClCa channels in vascular smooth muscle cells by calmodulin-dependent protein kinase II and calcineurin and how their fine tuning by these enzymes may influence vascular tone. Key words: calcium-activated chloride channels, vascular smooth muscle cells, ion channels, calmodulin-dependent protein kinase II, calcineurin

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Morel, Jean-Luc, Nathalie Mokrzycki, Guy Lippens, Hervé Drobecq, Pierre Sautière, and Michel Hugues. "Characterization of a Family of Scorpion Toxins Modulating Ca2+-Activated Cl− Current in Vascular Myocytes." Toxins 14, no. 11 (November 10, 2022): 780. http://dx.doi.org/10.3390/toxins14110780.

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The pharmacology of calcium-activated chloride current is not well developed. Peptides from scorpion venom present potent pharmacological actions on ionic conductance used to characterize the function of channels but can also be helpful to develop organic pharmacological tools. Using electrophysiological recording coupled with calcium measurement, we tested the potent effect of peptides extracted from Leuirus quinquestratus quinquestratus venom on the calcium-activated chloride current expressed in smooth muscle cells freshly dissociated from rat portal veins. We identified one peptide which selectively inhibited the chloride conductance without effects on either calcium signaling or calcium and potassium currents expressed in this cell type. The synthetic peptide had the same affinity, but the chemical modification of the amino acid sequence altered the efficiency to inhibit the calcium-activated chloride conductance.

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Loewen, Matthew E., Sherif E. Gabriel, and George W. Forsyth. "The calcium-dependent chloride conductance mediator pCLCA1." American Journal of Physiology-Cell Physiology 283, no. 2 (August 1, 2002): C412—C421. http://dx.doi.org/10.1152/ajpcell.00477.2001.

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The regulatory behavior, inhibitor sensitivity, and properties of the whole cell chloride conductance observed in cells expressing the cDNA coding for a chloride conductance mediator isoform of the CLCA gene family, pCLCA1, have been studied. Common C-kinase consensus phosphorylation sites between pCLCA1 and the closely related human isoform hCLCA1 are consistent with a role for calcium in channel activation. Both channels are activated rapidly on exposure to the calcium ionophore ionomycin. Direct involvement of calcium in the activation of pCLCA1 was supported by the finding that treatment with the intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid-AM reduced the rate of chloride efflux from NIH/3T3 cells expressing the pCLCA1 channel. No combination of A-kinase activators used was effective in activating chloride efflux via this channel despite the presence of a unique strong A-kinase consensus site in pCLCA1. Notable differences of pCLCA1 from the reported properties of CLCA family members include the failure of phorbol 12-myristate 13-acetate to activate chloride efflux in cells expressing pCLCA1 and a lack of inhibition of chloride efflux from these cells after treatment with DIDS or dithiothreitol. However, selected inhibitors of anionic conductance inhibited pCLCA1-dependent anion efflux. The electrogenic nature of the ionomycin-dependent efflux of chloride from cells expressing pCLCA1 was confirmed by detection of outwardly rectifying chloride current and inhibition of this current by chloride conductance inhibitors in a whole cell patch-clamp study.

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O'Driscoll, Kate E., William J. Hatton, Heather R. Burkin, Normand Leblanc, and Fiona C. Britton. "Expression, localization, and functional properties of Bestrophin 3 channel isolated from mouse heart." American Journal of Physiology-Cell Physiology 295, no. 6 (December 2008): C1610—C1624. http://dx.doi.org/10.1152/ajpcell.00461.2008.

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Bestrophins are a novel family of proteins that encode calcium-activated chloride channels. In this study we establish that Bestrophin transcripts are expressed in the mouse and human heart. Native mBest3 protein expression and localization in heart was demonstrated by using a specific polyclonal mBest3 antibody. Immunostaining of isolated cardiac myocytes indicates that mBest3 is present at the membrane. Using the patch-clamp technique, we characterized the biophysical and pharmacological properties of mBest3 cloned from heart. Whole cell chloride currents were evoked in both HEK293 and COS-7 cells expressing mBest3 by elevation of intracellular calcium. mBest3 currents displayed a KD for Ca2+ of ∼175 nM. The calcium-activated chloride current was found to be time and voltage independent and displayed slight outward rectification. The anion permeability sequence of the channel was SCN−>I−>Cl−, and the current was inhibited by niflumic acid and DIDS in the micromolar range. In addition, we generated a site-specific mutation (F80L) in the putative pore region of mBest3 that significantly altered the ion conduction and pharmacology of this channel. Our functional and mutational studies examining the biophysical properties of mBest3 indicate that it functions as a pore-forming chloride channel that is activated by physiological levels of calcium. This study reports novel findings regarding the molecular expression, tissue localization, and functional properties of mBest3 cloned from heart.

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Keating, N., and L. R. Quinlan. "Small conductance potassium channels drive ATP-activated chloride secretion in the oviduct." American Journal of Physiology-Cell Physiology 302, no. 1 (January 2012): C100—C109. http://dx.doi.org/10.1152/ajpcell.00503.2010.

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The molecular mechanisms controlling fluid secretion within the oviduct have yet to be determined. As in other epithelia, both secretory and absorptive pathways are likely to work in tandem to drive appropriate ionic movement to support fluid movement across the oviduct epithelium. This study explored the role of potassium channels in basolateral extracellular ATP (ATPe)-stimulated ion transport in bovine oviduct epithelium using the Ussing chamber short-circuit current ( ISC) technique. Basal ISC in bovine oviduct epithelium comprises both chloride secretion and sodium absorption and was inhibited by treatment with basolateral K+ channel inhibitors tetrapentlyammonium chloride (TPeA) or BaCl2. Similarly, ATP-stimulated chloride secretion was significantly attenuated by pretreatment with BaCl2, tetraethylammonium (TEA), tolbutamide, and TPeA. Basolateral K+ current, isolated using nystatin-perforation technique, was rapidly activated by ATPe, and pretreatment of monolayers with thapsigargin or TPeA abolished this ATP-stimulated K+ current. To further investigate the type of K+ channel involved in the ATP response in the bovine oviduct, a number of specific Ca2+-activated K+ channel inhibitors were tested on the ATP-induced Δ ISC in intact monolayers. Charbydotoxin, (high conductance and intermediate conductance inhibitor), or paxilline, (high conductance inhibitor) did not significantly alter the ATPe response. However, pretreatment with the small conductance inhibitor apamin resulted in a 60% reduction in the response to ATPe. The presence of small conductance family member KCNN3 was confirmed by RT-PCR and immunohistochemistry. Measurements of intracellular calcium using Fura-2 spectrofluorescence imaging revealed the ability of ATPe to increase intracellular calcium in a phospholipase C-inositol 1,4,5-trisphosphate pathway-sensitive manner. In conclusion, these results provide strong evidence that purinergic activation of a calcium-dependent, apamin-sensitive potassium conductance is essential to promote chloride secretion and thus fluid formation in the oviduct.

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Arreola, J., J. E. Melvin, and T. Begenisich. "Activation of calcium-dependent chloride channels in rat parotid acinar cells." Journal of General Physiology 108, no. 1 (July 1, 1996): 35–47. http://dx.doi.org/10.1085/jgp.108.1.35.

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The Ca2+ and voltage dependence of Ca(2+)-activated Cl- currents in rat parotid acinar cells was examined with the whole-cell patch clamp technique. Acinar cells were dialyzed with buffered free Ca2+ concentrations ([Ca2+]i) from < 1 nM to 5 microM. Increasing [Ca2+]i induced an increase in Cl- current at all membrane potentials. In cells dialyzed with [Ca2+]i > 25 nM, depolarizing test pulses activated a Cl- current that was composed of an instantaneous and a slow monoexponential component. The steady-state current-voltage relationship showed outward rectification at low [Ca2+]i but became more linear as the [Ca2+]i increased because of a shift in Cl- channel activation toward more negative voltages. The Ca2+ dependence of steady-state channel activation at various membrane voltages was fit by the Hill equation. The apparent Kd and Hill coefficient obtained from this analysis were both functions of membrane potential. The Kd decreased from 417 to 63 nM between -106 and +94 mV, whereas the Hill coefficient was always > 1 and increased to values as large as 2.5 at large positive potentials. We found that a relatively simple mechanistic model can account for the channel steady-state and kinetic behavior. In this model, channel activation involves two identical, independent, sequential Ca2+ binding steps before a final Ca(2+)-independent transition to the conducting conformation. Channel activation proceeds sequentially through three closed states before reaching the open state. The Ca2+ binding steps of this model have a voltage dependence similar to that of the Kd from the Hill analysis. The simplest interpretation of our findings is that these channels are directly activated by Ca2+ ions that bind to sites approximately 13% into the membrane electric field from the cytoplasmic surface.

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Nilius, B., J. Prenen, G. Szücs, L. Wei, F. Tanzi, T. Voets, and G. Droogmans. "Calcium-activated chloride channels in bovine pulmonary artery endothelial cells." Journal of Physiology 498, no. 2 (January 15, 1997): 381–96. http://dx.doi.org/10.1113/jphysiol.1997.sp021865.

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Cruz-Rangel, Silvia, José J. De Jesús-Pérez, Juan A. Contreras-Vite, Patricia Pérez-Cornejo, H. Criss Hartzell, and Jorge Arreola. "Gating modes of calcium-activated chloride channels TMEM16A and TMEM16B." Journal of Physiology 593, no. 24 (December 7, 2015): 5283–98. http://dx.doi.org/10.1113/jp271256.

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Dalati, S., and M. L. Day. "124. THE ROLE OF CALCIUM ACTIVATED CHLORIDE CHANNELS AT FERTILISATION." Reproduction, Fertility and Development 22, no. 9 (2010): 42. http://dx.doi.org/10.1071/srb10abs124.

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Sperm entry into the oocyte triggers a signal transduction pathway resulting in intracellular calcium [Ca2+] oscillations that coincide with hyperpolarisations in membrane potential (Em). Ca2+ oscillations have been previously described and found to be important for embryo development, yet Em hyperpolarisations and their importance at fertilisation still remains unclear. Thimerosal, a sulfhydryl reagent, has been shown to mimic the physiological changes caused by sperm following fertilisation. It does this by direct sensitisation of the inositol 1,4,5-triphosphate receptor-1 to basal levels of inositol 1,4,5-triphopshate. Previous patch clamp analysis of unfertilised mouse oocytes has shown that thimerosal elicits simultaneous Em hyperpolarisations and Ca2+ oscillations. These results have lead us to hypothesise that hyperpolarisations in Em may be due to the activation of a Ca2+ activated Cl- channel (CaCC) present in the membrane of mouse oocytes. The present study aims to identify this CaCC and assess its role in early development following fertilisation. Hyperpolarisations induced by thimerosal were inhibited by niflumic acid, a selective blocker of CaCCs. The inhibition of Em hyperpolarisations suggests that a CaCC is present and plays an active role in initiating hyperpolarisations. To identify the function of the CaCC at fertilisation, in vitro fertilisation was performed in the presence of niflumic acid. Niflumic acid inhibited polar body extrusion and pronuclei formation; two events that are indicators of fertilisation. Furthermore, Ca2+ imaging experiments with the calcium sensitive dye fura 2-AM, demonstrated that in the presence of niflumic acid, Ca2+ oscillations induced by thimerosal are reduced in size, number and duration. Taken together these data suggest that the activation of a Ca2+ activated Cl– channel in the mouse oocyte may play an important role in the events occurring at fertilisation.

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Sun, Yuyang, Lutz Birnbaumer, and Brij B. Singh. "TRPC1 regulates calcium‐activated chloride channels in salivary gland cells." Journal of Cellular Physiology 230, no. 11 (July 27, 2015): 2848–56. http://dx.doi.org/10.1002/jcp.25017.

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Kamaleddin, Mohammad Amin. "Molecular, biophysical, and pharmacological properties of calcium-activated chloride channels." Journal of Cellular Physiology 233, no. 2 (May 15, 2017): 787–98. http://dx.doi.org/10.1002/jcp.25823.

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Journal articles on the topic 'Calcium activated chlorine channels'

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