共查询到20条相似文献,搜索用时 31 毫秒
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Anatoly Soloviev Sergey Tishkin Irina Ivanova Sergey Zelensky Victor Dosenko Sergey Kyrychenko Robert S. Moreland 《Life sciences》2009,84(5-6):164-171
AimsThe goal of this study was to evaluate the influence of γ-irradiation on Ca2+-activated K+ channel (BKCa) function and expression in rat thoracic aorta.Main methodsAortic cells or tissues were studied by the measurement of force versus [Ca2+]i, patch-clamp technique, and RT-PCR.Key findingsStimulation of smooth muscle cells with depolarizing voltage steps showed expression of outward K+ currents. Paxilline, an inhibitor of BKCa channels, decreased outward K+ current density. Outward currents in smooth muscle cells obtained from irradiated animals 9 and 30 days following radiation exposure demonstrated a significant decrease in K+ current density. Paxilline decreased K+ current in cells obtained 9 days, but was without effect 30 days after irradiation suggesting the absence of BKCa channels. Aortic tissue from irradiated animals showed progressively enhanced contractile responses to phenylephrine in the post-irradiation period of 9 and 30 days. The concomitant Ca2+ transients were significantly smaller, as compared to tissues from control animals, 9 days following irradiation but were increased above control levels 30 days following irradiation. Irradiation produced a decrease in BKCa α- and β1-subunit mRNA levels in aortic smooth muscle cells suggesting that the vasorelaxant effect of these channels may be diminished.SignificanceThese results suggest that the enhanced contractility of vascular tissue from animals exposed to radiation may result from an increase in myofilament Ca2+ sensitivity in the early post-irradiation period and a decrease in BKCa channel expression in the late post-irradiation period. 相似文献
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Differential expression and regulatory roles of FABP5 and FABP7 in oligodendrocyte lineage cells 总被引:1,自引:0,他引:1
Kazem Sharifi Majid Ebrahimi Yoshiteru Kagawa Ariful Islam Tuerhong Tuerxun Yuki Yasumoto Tomonori Hara Yui Yamamoto Hirofumi Miyazaki Nobuko Tokuda Takeo Yoshikawa Yuji Owada 《Cell and tissue research》2013,354(3):683-695
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JENNIFER DUMONT DAVID COHEN JOËLLE GÉRARD YVES JOLIVET PIERRE DIZENGREMEL DIDIER LE THIEC 《Plant, cell & environment》2014,37(9):2064-2076
Ozone induces stomatal sluggishness, which impacts photosynthesis and transpiration. Stomatal responses to variation of environmental parameters are slowed and reduced by ozone and may be linked to difference of ozone sensitivity. Here we determine the ozone effects on stomatal conductance of each leaf surface. Potential causes of this sluggish movement, such as ultrastructural or ionic fluxes modification, were studied independently on both leaf surfaces of three Euramerican poplar genotypes differing in ozone sensitivity and in stomatal behaviour. The element contents in guard cells were linked to the gene expression of ion channels and transporters involved in stomatal movements, directly in microdissected stomata. In response to ozone, we found a decrease in the stomatal conductance of the leaf adaxial surface correlated with high calcium content in guard cells compared with a slight decrease on the abaxial surface. No ultrastructural modifications of stomata were shown except an increase in the number of mitochondria. The expression of vacuolar H+/Ca2+‐antiports (CAX1 and CAX3 homologs), β‐carbonic anhydrases (βCA1 and βCA4) and proton H+‐ATPase (AHA11) genes was strongly decreased under ozone treatment. The sensitive genotype characterized by constitutive slow stomatal response was also characterized by constitutive low expression of genes encoding vacuolar H+/Ca2+‐antiports. 相似文献
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Scorpion toxins, the basic miniprotiens of scorpion venom, stimulated the passive uptake of Na+ and Ca2+ in chick ermbryo heart cells. Half-maximum stimulation was obtained for 20–30 nM Na+ and 40–50 nM Ca2+. Scorpion toxin-activated Na+ and Ca2+ uptakes were fully inhibited by tetrodotoxin, a specific inhibitor of the action potential Na+ ionophore in excitable membranes. Half-maximum inhibition was obtained with the same concentration of tetrodotoxin (10 nm) for both Na+ and Ca2+. Scorpion toxin-stimulated Ca2+ uptake was dependent on extracellular Na+ concentration and was not inhibited by Ca2+ channel blocking drugs which are inactive on heart cell action potential. Thus, in heart cells scorpion toxin affects the passive Ca2+ transport, which is coupled to passive Na+ ionphore. Other results suggest that (1) tetrodotoxin and scorpion toxin bind to different sites of the sarcolemma and (2) binding of scorpion toxin to its specific sites may unmask latent tetrodotoxin — sensitive fast channels. 相似文献
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A large-conductance, Ca2+-activated K+ channel was identified and characterized in embryonic chick hepatocytes using the patch-electrode voltage-clamp technique. The channel conductance was 213 pS in excised patches bathed in symmetrical 145 mM KCl and 1 mM Ca2+. Current-voltage relationships were linear with high K+ on both sides of the membrane but showed constant field rectification as the K+ gradient was increased. The reversal potential shifted 58 mV per 10-fold change in the ratio of external to internal K+. Channel openings occurred at potentials higher than +50 mV in cell-attached patches. The open probability × voltage relationship shifted to more negative potentials in excised, inside-out patches exposed to a solution containing high Ca2+. The voltage sensitivity of the channel was not significantly affected by changes in internal Ca2+ concentration. Conversely, channel gating, reflected in the half-activation potential, shifted 118 mV per 10-fold change in internal Ca2+ at concentrations less than ∼2 μM, although at higher Ca2+, this parameter was Ca2+ insensitive. Channel open probability in cell-attached patches increased significantly following exposure of the cells to either the Ca2+ ionophore A-23187 or L-alanine, a cell-volume modulator. Channel density increased with time spent in culture from no observations in 10-hr cells, through 13 and 80% of patches in 24-and 48-hr cultured cells, respectively. The implications of delayed functional expression for ion channel studies in acutely dissociated cells is discussed. J. Cell. Physiol. 171:87–94, 1997. © 1997 Wiley-Liss, Inc. 相似文献
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Bongkrekic acid and atractyloside, inhibitors of adenine nucleotide translocase, do not inhibit Ca2+ uptake and H+ production by pig heart mitochondria. However, bongkrekic acid, but not atractyloside, inhibits dinitrophenol-induced Ca2+ efflux and H+ uptake. Conversely, ruthenium red blocks Ca2+ uptake and H+ production but does not prevent dinitrophenol-induced Ca2+ efflux and H+ uptake by mitochondria. These results suggest that mitochondrial Ca2+ uptake and release exist as two independent pathways. The efflux of Ca2+ from mitochondria is mediated by a bongkrekic acid sensitive component which is apparently not identical to the ruthenium red sensitive Ca2+ uptake carrier. 相似文献
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Little is known about the role of mitogen-activated protein kinase 6 (MPK6) in Na+ toxicity and inhibition of root growth in Arabidopsis under NaCl stress. In this study, we found that root elongation in seedlings of the loss-of-function mutants mpk6-2 and mpk6-3 was less sensitive to NaCl or Na-glutamate, but not to KCl or mannitol, as compared with that of wild-type (WT) seedlings. The less sensitive characteristic was eliminated by adding the Ca2+ chelator EGTA or the Ca2+ channel inhibitor LaCl3, but not the Ca2+ ionophore A23187. This suggested that the tolerance of mpk6 to Na+ toxicity was Ca2+-dependent. We measured plasma membrane (PM) Na+-conducted currents (NCCs) in root cells. Increased concentrations of NaCl increased the inward NCCs while decreased the outward NCCs in WT root cells, attended by a positive shift in membrane potential. In mpk6 root cells, NaCl significantly increased outward but not inward NCCs, accompanied by a negative shift in membrane potential. That is, mpk6 decreased NaCl-induced the Na+ accumulation by modifying PM Na+ flux in root cells. Observations of aequorin luminescence revealed a NaCl-induced increase of cytosolic Ca2+ in mpk6 root cells, resulting from PM Ca2+ influx. An increase of cytosolic Ca2+ was required to alleviate the NaCl-increased Na+ content and Na+/K+ ratio in mpk6 roots. Together, these results show that mpk6 accumulated less Na+ in response to NaCl because of the increased cytosolic Ca2+ level in root cells; thus, its root elongation was less inhibited than that of WT by NaCl. 相似文献
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Tetrodotoxin-resistant sodium channels 总被引:4,自引:0,他引:4
Shigeru Yoshida 《Cellular and molecular neurobiology》1994,14(3):227-244
Summary 1. Tetrodotoxin (TTX) has been widely used as a chemical tool for blocking Na+ channels. However, reports are accumulating that some Na+ channels are resistant to TTX in various tissues and in different animal species. Studying the sensitivity of Na+ channels to TTX may provide us with an insight into the evolution of Na+ channels.2. Na+ channels present in TTX-carrying animals such as pufferfish and some types of shellfish, frogs, salamanders, octopuses, etc., are resistant to TTX.3. Denervation converts TTX-sensitive Na+ channels to TTX-resistant ones in skeletal muscle cells, i.e., reverting-back phenomenon. Also, undifferentiated skeletal muscle cells contain TTX-resistant Na+ channels. Cardiac muscle cells and some types of smooth muscle cells are considerably insensitive to TTX.4. TTX-resistant Na+ channels have been found in cell bodies of many peripheral nervous system (PNS) neurons in both immature and mature animals. However, TTX-resistant Na+ channels have been reported in only a few types of central nervous system (CNS). Axons of PNS and CNS neurons are sensitive to TTX. However, some glial cells have TTX-resistant Na+ channels.5. Properties of TTX-sensitive and TTX-resistant Na+ channels are different. Like Ca2+ channels, TTX-resistant Na+ channels can be blocked by inorganic (Co2+, Mn2+, Ni2+, Cd2+, Zn2+, La3+) and organic (D-600) Ca2+ channel blockers. Usually, TTX-resistant Na+ channels show smaller single-channel conductance, slower kinetics, and a more positive current-voltage relation than TTX-sensitive ones.6. Molecular aspects of the TTX-resistant Na+ channel have been described. The structure of the channel has been revealed, and changing its amino acid(s) alters the sensitivity of the Na+ channel to TTX.7. TTX-sensitive Na+ channels seem to be used preferentially in differentiated cells and in higher animals instead of TTX-resistant Na+ channels for rapid and effective processing of information.8. Possible evolution courses for Na+ and Ca2+ channels are discussed with regard to ontogenesis and phylogenesis. 相似文献
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Dan A. Klaerke Hubert Wiener Thomas Zeuthen Peter L. Jørgensen 《The Journal of membrane biology》1993,136(1):9-21
To determine if their properties are consistent with a role in regulation of transepithelial transport, Ca2+-activated K+ channels from the basolateral plasma membrane of the surface cells in the distal colon have been characterized by single channel analysis after fusion of vesicles with planar lipid bilayers. A Ca2+-activated K+ channel with a single channel conductance of 275 pS was predominant. The sensitivity to Ca2+ was strongly dependent on the membrane potential and on the pH. At a neutral pH, the K
0.5 for Ca2+ was raised from 20nm at a potential of 0 mV to 300nm at –40 mV. A decrease in pH at the cytoplasmic face of the K+ channel reduced the Ca2+ sensitivity dramatically. A loss of the high sensitivity to Ca2+ was also observed after incubation with MgCl2, possibly a result of dephosphorylation of the channels by endogenous phosphatases. Modification of the channel protein may thus explain the variation in Ca2+ sensitivity between studies on K+ channels from the same tissue. High affinity inhibition (K
0.5=10nm) by charybdotoxin of the Ca2+-activated K+ channel from the extracellular face could be lifted by an outward flux of K+ through the channel. However, at the ion gradients and potentials found in the intact epithelium, charybdotoxin should be a useful tool for examination of the role of maxi K+ channels. The high sensitivity for Ca2+ and the properties of the activator site are in agreement with an important regulatory role for the high conductance K+ channel in the epithelial cells.Dr. E. Moczydlowsky, Yale University School of Medicine, New Haven, CT, and Dr. Per Stampe, Brandeis University, Waltham, MA, are thanked for introduction to the bilayer technique. Tove Soland is thanked for excellent technical assistance. This work was supported by the Novo Nordisk Foundation, the Carlsberg Foundation, the Danish Medical Research Council, and the Austrian Research Council. 相似文献
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The Ca2+-activated maxi K+ channel is predominant in the basolateral membrane of the surface cells in the distal colon. It may play a role in the regulation
of the aldosterone-stimulated Na+ reabsorption from the intestinal lumen. Previous measurements of these basolateral K+ channels in planar lipid bilayers and in plasma membrane vesicles have shown a very high sensitivity to Ca2+ with a K
0.5 ranging from 20 nm to 300 nm, whereas other studies have a much lower sensitivity to Ca2+. To investigate whether this difference could be due to modulation by second messenger systems, the effect of phosphorylation
and dephosphorylation was examined. After addition of phosphatase, the K+ channels lost their high sensitivity to Ca2+, yet they could still be activated by high concentrations of Ca2+ (10 μm). Furthermore, the high sensitivity to Ca2+ could be restored after phosphorylation catalyzed by a cAMP dependent protein kinase. There was no effect of addition of
protein kinase C. In agreement with the involvement of enzymatic processes, lag periods of 30–120 sec for dephosphorylation
and of 10–280 sec for phosphorylation were observed. The phosphorylation state of the channel did not influence the single
channel conductance. The results demonstrate that the high sensitivity to Ca2+ of the maxi K+ channel from rabbit distal colon is a property of the phosphorylated form of the channel protein, and that the difference
in Ca2+ sensitivity between the dephosphorylated and phosphorylated forms of the channel protein is more than one order of magnitude.
The variety in Ca2+ sensitivities for maxi K+ channels from tissue to tissue and from different studies on the same tissue could be due to modification by second messenger
systems.
Received: 28 February 1995/Revised: 22 December 1995 相似文献
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Victor P.T. Pau Karin Abarca-Heidemann Brad S. Rothberg 《The Journal of general physiology》2010,135(5):509-526
MthK is a Ca2+-gated K+ channel whose activity is inhibited by cytoplasmic H+. To determine possible mechanisms underlying the channel’s proton sensitivity and the relation between H+ inhibition and Ca2+-dependent gating, we recorded current through MthK channels incorporated into planar lipid bilayers. Each bilayer recording was obtained at up to six different [Ca2+] (ranging from nominally 0 to 30 mM) at a given [H+], in which the solutions bathing the cytoplasmic side of the channels were changed via a perfusion system to ensure complete solution exchanges. We observed a steep relation between [Ca2+] and open probability (Po), with a mean Hill coefficient (nH) of 9.9 ± 0.9. Neither the maximal Po (0.93 ± 0.005) nor nH changed significantly as a function of [H+] over pH ranging from 6.5 to 9.0. In addition, MthK channel activation in the nominal absence of Ca2+ was not H+ sensitive over pH ranging from 7.3 to 9.0. However, increasing [H+] raised the EC50 for Ca2+ activation by ∼4.7-fold per tenfold increase in [H+], displaying a linear relation between log(EC50) and log([H+]) (i.e., pH) over pH ranging from 6.5 to 9.0. Collectively, these results suggest that H+ binding does not directly modulate either the channel’s closed–open equilibrium or the allosteric coupling between Ca2+ binding and channel opening. We can account for the Ca2+ activation and proton sensitivity of MthK gating quantitatively by assuming that Ca2+ allosterically activates MthK, whereas H+ opposes activation by destabilizing the binding of Ca2+. 相似文献
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Genetically identical cells in a uniform external environment can exhibit different phenotypes, which are often masked by conventional measurements that average over cell populations. Although most studies on this topic have used microorganisms, differentiated mammalian cells have rarely been explored. Here, we report that only approximately 40% of clonal human embryonic kidney 293 cells respond with an intracellular Ca2+ increase when ryanodine receptor Ca2+ release channels in the endoplasmic reticulum are maximally activated by caffeine. On the other hand, the expression levels of ryanodine receptor showed a unimodal distribution. We showed that the difference in the caffeine sensitivity depends on a critical balance between Ca2+ release and Ca2+ uptake activities, which is amplified by the regenerative nature of the Ca2+ release mechanism. Furthermore, individual cells switched between the caffeine‐sensitive and caffeine‐insensitive states with an average transition time of approximately 65 h, suggestive of temporal fluctuation in endogenous protein expression levels associated with caffeine response. These results suggest the significance of regenerative mechanisms that amplify protein expression noise and induce cell‐to‐cell phenotypic variation in mammalian cells. 相似文献
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Summary (i) In human red cell membranes the sensitivity to N-ethylmaleimide of Ca2+-dependent ATPase and phosphatase activities is at least ten times larger than the sensitivity to N-ethylmaleimide of (Na++K+)-ATPase and K+-activated phosphatase activities. All activities are partially protected against N-ethylmaleimide by ATP but not by inorganic phosphate or byp-nitrophenylphosphate. (ii) Protection by ATP of (Na++K+)-ATPase is impeded by either Na+ or K+ whereas only K+ impedes protection by ATP of K+-activated phosphatase. On the other hand, Na+ or K+ slightly protects Ca2+-dependent activities against N-ethylmaleimide, this effect being independent of ATP. (iii) The sensitivity to N-ethylmaleimide of Ca2+-dependent ATPase and phosphatase activities is markedly enhanced by low concentrations of Ca2+. This effect is half-maximal at less than 1 m Ca2+ and does not require ATP, which suggests that sites with high affinity for Ca2+ exist in the Ca2+-ATPase in the absence of ATP. (iv) Under all conditions tested the response to N-ethylmaleimide of the ATPase and phosphatase activites stimulated by K+ or Na+ in the presence of Ca2+ parallels that of the Ca2+-dependent activities, suggesting that the Ca2+-ATPase system possesses sites at which monovalent cations bind to increase its activity. 相似文献
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Jonathan Berrout Mykola Mamenko Oleg L. Zaika Lihe Chen Wenzheng Zang Oleh Pochynyuk Roger G. O'Neil 《PloS one》2014,9(4)
The Ca2+-activated, maxi-K (BK) K+ channel, with low Ca2+-binding affinity, is expressed in the distal tubule of the nephron and contributes to flow-dependent K+ secretion. In the present study we demonstrate that the Ca2+-activated, SK3 (KCa2.3) K+ channel, with high Ca2+-binding affinity, is also expressed in the mouse kidney (RT-PCR, immunoblots). Immunohistochemical evaluations using tubule specific markers demonstrate significant expression of SK3 in the distal tubule and the entire collecting duct system, including the connecting tubule (CNT) and cortical collecting duct (CCD). In CNT and CCD, main sites for K+ secretion, the highest levels of expression were along the apical (luminal) cell membranes, including for both principal cells (PCs) and intercalated cells (ICs), posturing the channel for Ca2+-dependent K+ secretion. Fluorescent assessment of cell membrane potential in native, split-opened CCD, demonstrated that selective activation of the Ca2+-permeable TRPV4 channel, thereby inducing Ca2+ influx and elevating intracellular Ca2+ levels, activated both the SK3 channel and the BK channel leading to hyperpolarization of the cell membrane. The hyperpolarization response was decreased to a similar extent by either inhibition of SK3 channel with the selective SK antagonist, apamin, or by inhibition of the BK channel with the selective antagonist, iberiotoxin (IbTX). Addition of both inhibitors produced a further depolarization, indicating cooperative effects of the two channels on Vm. It is concluded that SK3 is functionally expressed in the distal nephron and collecting ducts where induction of TRPV4-mediated Ca2+ influx, leading to elevated intracellular Ca2+ levels, activates this high Ca2+-affinity K+ channel. Further, with sites of expression localized to the apical cell membrane, especially in the CNT and CCD, SK3 is poised to be a key pathway for Ca2+-dependent regulation of membrane potential and K+ secretion. 相似文献
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Sarah Kircher Maylin Merino-Wong Barbara A. Niemeyer Dalia Alansary 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2018,1865(6):932-943
Differentiation of naïve CD4+ T cells into effector subtypes with distinct cytokine profiles and physiological roles is a tightly regulated process, the imbalance of which can lead to an inadequate immune response or autoimmune disease. The crucial role of Ca2+ signals, mainly mediated by the store operated Ca2+ entry (SOCE) in shaping the immune response is well described. However, it is unclear if human effector CD4+ T cell subsets show differential Ca2+ signatures in response to different stimulation methods. Herein, we provide optimized in vitro culture conditions for polarization of human CD4+ effector T cells and characterize their SOCE following both pharmacological store depletion and direct T-cell receptor (TCR) activation. Moreover, we measured whole cell Ca2+ release activated Ca2+ currents (ICRAC) and investigated whether the observed differences correlate to the expression of CRAC genes. Our results show that Ca2+ profiles of helper CD4+ Th1, Th2 and Th17 are distinct and in part shaped by the intensity of stimulation. Regulatory T cells (Treg) are unique being the subtype with the most prominent SOCE response. Analysis of in vivo differentiated Treg unraveled the role of differential expression of ORAI2 in fine-tuning signals in Treg vs. conventional CD4+ T cells. 相似文献
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Abstract– The uptake of 45Ca2+ into cell suspensions prepared from a transplantable rat pheochromocytoma was measured. The uptake of Ca2+ into these cells is biphasic; there is a rapid, initial uptake of Ca+, followed by a slower uptake that proceeds at a linear rate for at least 10min at 37°C. The uptake of Ca2+ is a linear function of the external Ca2+ concentration over the range of 0.13-2.5 mm -Ca2+ Incubation of the cells in a medium containing 56mm -K+ results in a 2-3 fold increase in the uptake of Ca2+ into the cells; 56mm -K+ increases both phases of Ca2+ uptake. The cells apparently lack a mechanism to inactivate this 56 mm -K+-induced increase-in Ca2+ permeability. Two inhibitors of K+ stimulated catecholamine secretion, diphenylhydantoin and verapamil, both inhibit K +-stimulated Ca2+ uptake. These results provide a direct demonstration of the stimulus-coupled uptake of Ca2+ into chromaffin cells, and provide additional evidence for the correlation of Ca2+ uptake with catecholamine secretion by these cells. 相似文献