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1.
Yasuo Nakaoka Kenji Iwatsuki 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(6):723-727
Summary In order to study the relationship between the inward Ca current activated by hyperpolarization and the frequency increase in ciliary beating, Paramecium cells were voltage clamped under conditions where K current was suppressed by use of CsCl electrodes and by extracellular tetraethyl ammonium. A 2-s pulse of hyperpolarization from the resting potential activated an inward current consisting of two components, an initial transient current peaking at 0.1–0.2 s (which had been identified as a Ca current) and a subsequent sustained current. The initial component was not associated with the frequency increase because the frequency increase was normally induced even when the peak current was almost completely inhibited by external addition of Ba2+. The second sustained current was closely correlated with the frequency increase. The frequency rose steeply with the sustained current and saturated at –0.6 nA. External addition of La3+ or replacement of Ca2+ by Mg2+ suppressed this current, and at the same time the frequency increase was inhibited. As the amplitude of the sustained current was not changed by deciliation, this current must pass through the somatic membrane. These results suggest that the frequency increase upon hyperpolarization is triggered by the voltage-activated inward current passing through the somatic membrane of the interciliary compartment.Abbreviations cAMP
cyclic adenosine monophosphate
- HEPES
hydroxyethylpiperazine ethanesulfonate
- TEA+
tetraethyl ammonium 相似文献
2.
M. V. Wright N. Elwess J. van Houten 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):288-296
Intracellular Ca2+ levels in Paramecium must be tightly controlled, yet little is understood about the mechanisms of control. We describe here indirect evidence that a phosphoenzyme intermediate is the calmodulin-regulated plasma membrane Ca2+ pump and that a Ca2+-ATPase activity in pellicles (the complex of cell body surface membranes) is the enzyme correlate of the plasma membrane pump protein. A change in Ca2+ pump activity has been implicated in the chemoresponse of paramecia to some attractant stimuli. Indirect support for this is demonstrated using mutants with different modifications of calmodulin to correlate defects in chemoresponse with altered Ca2+ homeostasis and pump activity.Abbreviations EGTA
ethyleneglycol tetra-acetate
- ER
endoplasmic reticulum
- IBMX
isobutyl methylxanthine
-
I
che
index of chemokinesis
- Mops
3-[N-morpholino] propanesulfonic acid
- PEI
phosphoenzyme intermediate
- STEN
sucrose, TRIS, EDTA, sodium chloride
- TCA
trichloroacetic acid
- TRIS
tris[hydroxymethyl] aminomethane 相似文献
3.
Support from the National Institutes of Health and the American Heart Association is gratefully acknowledged. 相似文献
4.
Naranjan S. Dhalla Vincenzo Panagia Naoki Makino Robert E. Beamish 《Molecular and cellular biochemistry》1988,82(1-2):75-79
In order to identify defects in Na+-Ca2+ exchange and Ca2+-pump systems in cardiomyopathic hearts, the activities of sarcolemmal Na+-dependent Ca2+ uptake, Na+-induced Ca2+ release, ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase were examined by employing cardiomyopathic hamsters (UM-X7.1) and catecholamine-induced cardiomyopathy produced by injecting isoproterenol into rats. The rates of Na+-dependent Ca2+ uptake, ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase activities of sarcolemmal vesicles from genetically-linked cardiomyopathic as well as catecholamine-induced cardiomyopathic hearts were decreased without any changes in Na+-induced Ca2+-release. Similar results were obtained in Ca2+-paradox when isolated rat hearts were perfused for 5 min with a medium containing 1.25 mM Ca2+ following a 5 min perfusion with Ca2+-free medium. Although a 2 min reperfusion of the Ca2+-free perfused hearts depressed sarcolemmal Ca2+-pump activities without any changes in Na+-induced Ca2+-release, Na+-dependent Ca2+ uptake was increased. These results indicate that alterations in the sarcolemmal Ca2+-efflux mechanisms may play an important role in cardiomyopathies associated with the development of intracellular Ca2+ overload. 相似文献
5.
Yat H. Lau 《生物化学与生物物理学报:生物膜》1983,730(2)
Ca2+ transport by sarcoplasmic reticulum vesicles was examined by incubating sarcoplasmic reticulum vesicles (0.15 mg/ml) at 37°C in, either normal medium that contained 0.15 M sucrose, 0.1 M KCl, 60 μM CaCl2, 2.5 mM ATP and 30 mM Tes at pH 6.8, or a modified medium for elimination of ADP formed from ATP hydrolysis by including, in addition, 3.6 mM phosphocreatine and 33 U/ml of creatine phosphokinase. In normal medium, Ca2+ uptake of sarcoplasmic reticulum vesicles reached a plateau of about 100 nmol/mg. In modified medium, after this phase of Ca2+ uptake, a second phase of Ca2+ accumulation was initiated and reached a plateau of about 300 nmol/mg. The second phase of Ca2+ accumulation was accompanied by phosphate uptake and could be inhibited by ADP. Since, under these experimental conditions, there was no significant difference of the rates of ATP hydrolysis in normal medium and modified medium, extra Ca2+ uptake in modified medium but not in normal medium could not be explained by different phosphate accumulation in the two media. Unidirectional Ca2+ influx of sarcoplasmic reticulum near steady state of Ca2+ uptake was measured by pulse labeling with 45Ca2+. The Ca2+ efflux rate was then determined by subtracting the net uptake from the influx rate. At the first plateau of Ca2+ uptake in normal medium, Ca2+ influx was balanced by Ca2+ efflux with an exchange rate of 240 nmol/mg per min. This exchange rate was maintained relatively constant at the plateau phase. In modified medium, the Ca2+ exchange rate at the first plateau of Ca2+ uptake was about half of that in normal medium. When the second phase of Ca2+ uptake was initiated, both the influx and efflux rates started to increase and reached a similar exchange rate as observed in normal medium. Also, during the second phase of Ca2+ uptake, the difference between the influx and efflux rates continued to increase until the second plateau phase was approached. In conditions where the formation of ADP and inorganic phosphate was minimized by using a low concentration of sarcoplasmic (7.5 μg/ml) and/or using acetyl phosphate instead of ATP, the second phase of Ca2+ uptake was also observed. These data suggest that the Ca2+ load attained by sarcoplasmic reticulum vesicles during active transport is modulated by ADP accumulated from ATP hydrolysis. ADP probably exerts its effect by facilitating Ca2+ efflux, which subsequently stimulates Ca2+ exchange. 相似文献
6.
Nicholas Sperelakis Zhiling Xiong G. Haddad Hiroshi Masuda 《Molecular and cellular biochemistry》1994,140(2):103-117
The slow Ca2+ channels (L-type) of the heart are stimulated by cAMP. Elevation of cAMP produces a very rapid increase in number of slow channels available for voltage activation during excitation. The probability of a Ca2+ channel opening and the mean open time of the channel are increased. Therefore, any agent that increases the cAMP level of the myocardial cell will tend to potentiate ICa, Ca2+ influx, and contraction. The action of cAMP is mediated by PK-A and phosphorylation of the slow Ca2+ channel protein or an associated regulatory protein (stimulatory type). The myocardial slow Ca2+ channels are also rogulated by cGMP, in a manner that is opposite orantagonistic to that of cAMP. We have demonstrated this at both the macroscople level (whole-cell voltage clamp) and the single-channel level. The effect of cGMP is mediated by PK-G and phosphorylation of a protein, as for example, a regulatory protein (inhibitory-type) associated with the Ca2+ channel. Introduction of PK-G intracellularly causes a relatively rapid inhibition of ICa(L) in both chick and rat heart cells. Such inhibition occurs for both the basal and stimulated ICa(L). In addition, the cGMP/PK-G system was reported to stimulate a phosphatase that dephosphorylates the Ca2+ channel. In addition to the slower indirect pathway—exerted via cAMP/PK-A—there is a faster more-direct pathway for ICa(L) stimulation by the -adrenergic receptor. This latter pathway involves direct modulation of the channel activity by the alpha subunit (s*) of the Gs-protein. In vascular smooth muscle cells the two pathways (direct and indirect) also appear to be present, although the indirect pathway producesinhibition of ICa(L). PK-C and calmodulin-PK also may play roles in regulation of the myocardial slow Ca2+ channels. Both of these protein kinases stimulate the activity of these channels. Thus, it appears that the slow Ca2+ channel is a complex structure, including perhaps several associated regulatory proteins, which can be regulated by a number of factors intrinsic and extrinsic to the cell, and thereby control can be exercised over the force of contraction of the heart.This review-type article was prepared by modifying an article published in a book by Sperelakiset al., 1994. 相似文献
7.
Kana Sugimoto Hidekazu Tanaka Hiroshi Ochi Ryoji Matoba 《Biochemical and biophysical research communications》2009,390(4):1214-1807
Methamphetamine induces several cardiac dysfunctions, which leads to arrhythmia, cardiac failure and sudden cardiac death. Although these cardiac alterations elicited by methamphetamine were thought to be due to an indirect action of methamphetamine, namely, an excessive catecholamine release from synaptic terminals, while it seems likely that methamphetamine directly modulates the functioning of cardiomyocytes independent of neurotransmitters. However, the direct effects of methamphetamine on cardiomyocytes are still not clear. We show that methamphetamine directly accelerates the beating rate and alters Ca2+ oscillation pattern in cultured neonatal rat cardiomyocytes. Adrenergic receptor antagonists did not block the methamphetamine-induced alterations in cardiomyocytes. Treatment with a ryanodine receptor type 2 inhibitor and a sarcoplasmic reticulum Ca2+-ATPase inhibitor did not affect these responses, either. In contrast, the L-type Ca2+ channel inhibitor nifedipine eradicated these responses. Furthermore, methamphetamine elevated the internal free Ca2+ concentration in HEK-293T cells stably transfected with the L-type Ca2+ channel α1C subunit. In neonatal rat cardiomyocytes, methamphetamine accelerates beating rate and alters Ca2+ oscillation pattern by increasing Ca2+ entry via the L-type Ca2+ channels independent of any neurotransmitters. 相似文献
8.
Tiit Laasberg 《Development genes and evolution》1987,196(7):464-466
Summary Exogeneous cyclic AMP (cAMP, 10–8M), when added together with acetylcholine (ACh, 500 M) to dissociated chick embryo cells, blocked the ACh-stimulated increase in the level of cytosolic free Ca2+ ([Ca2+]i). This inhibiting action of exogeneous cAMP is probably mediated by intracellular cyclic GMP (cGMP) and cAMP. 相似文献
9.
Yoshihiro Mogami Hans Machemer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(6):687-695
Summary Motor responses of cirri (= organelles consisting of bundles of cilia) in the protozoan Stylonychia are elicited by positive or negative shifts of the membrane voltage from its resting state. The same responses are evoked at voltages near the Ca2+ equilibrium potential (ECa) applying extremely positive steps under voltage clamp. Motor responses recorded at large positive voltages approaching ECa from the negative side corresponded to cirral activation following physiological depolarization from the resting potential (DCA). The hyperpolarization-induced activation of the cirri (HCA) was documented during step potentials positive to ECa, suggesting that the observed HCA of the cirri resulted from an efflux of Ca2+ from the ciliary space as compared with DCA, which is related to Ca2+ influx. The ciliary responses were graded functions of the rising outward or inward driving force for Ca2+. Slopes of reciprocal plots of response latencies near ECa as a function of membrane potential indicate a removal of Ca2+ during HCA which exceeds the free intraciliary Ca2+ content at rest. It is suggested that this excess Ca2+ is released from axonemal binding sites. 相似文献
10.
Effect of nordihydroguaiaretic acid on intracellular Ca concentrations in C6 glioma cells 总被引:1,自引:0,他引:1
Warren Su Li-Ling Tseng Muh-Chiou Lin Hsin-Ju Chang Kam-Chung Lee Kang-Ju Chou Yuk-Keung Lo Jin-Shiung Cheng Hong-Tai Chang Jue-Long Wang Chun-Peng Liu Wei-Chung Chen Chung-Ren Jan 《Neurochemistry international》2002,40(3):249-254
The effect of nordihydroguaiaretic acid (NDGA) on Ca(2+) signaling in C6 glioma cells has been investigated. NDGA (5-100 microM) increased [Ca(2+)]i concentration-dependently. The [Ca(2+)]i increase comprised an initial rise and an elevated phase over a time period of 4 min. Removal of extracellular Ca(2+) reduced NDGA-induced [Ca(2+)]i signals by 52+/-2%. After incubation of cells with NDGA in Ca(2+)-free medium for 4 min, addition of 3 mM CaCl2 induced a concentration-dependent increase in [Ca(2+)]i. NDGA (100 microM)-induced [Ca(2+)]i increases in Ca(2+)-containing medium was not changed by pretreatment with 10 microM nifedipine or verapamil. In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (1 microM) abolished 100 microM NDGA-induced [Ca(2+)]i increases. Inhibition of phospholipase C with 2 microM U73122 had little effect on 100 microM NDGA-induced Ca(2+) release. Several other lipoxygenase inhibitors had no effect on basal [Ca(2+)]i. Collectively, the results suggest that NDGA increased [Ca(2+)]i in glioma cells in a lipoxygenase-independent manner, by releasing Ca(2+) from the endoplasmic reticulum in a manner independent of phospholipase C activity and by causing Ca(2+) influx. 相似文献
11.
The actions of the protonophore CCCP on intracellular Ca2+ regulation and exocytosis in chromaffin cells have been examined. Simultaneous fura-2 imaging and amperometry reveal that exposure to CCCP not only perturbs mitochondrial function but that it also alters vesicular storage of Ca2+ and catecholamines. By disrupting the pH gradient of the secretory vesicle membrane, the protonophore allows both Ca(2+) and catecholamine to leak into the cytosol. Unlike the high cytosolic Ca2+ concentrations resulting from mitochondrial membrane disruption, Ca2+ leakage from secretory vesicles may initiate exocytotic release. In conjunction with previous studies, this work reveals that catalytic and self-sustained vesicular Ca(2+) -induced exocytosis occurs with extended exposure to weak acid or base protonophores. 相似文献
12.
《Electromagnetic biology and medicine》2013,32(1):77-84
AbstractCalcium transients play an essential role in cardiomyocytes and electromagnetic fields (EMF) and affect intracellular calcium levels in many types of cells. Effects of EMF on intracellular calcium transients in cardiomyocytes are not well studied. The aim of this study was to assess whether extremely low frequency electromagnetic fields (ELF-EMF) could affect intracellular calcium transients in cardiomyocytes. Cardiomyocytes isolated from neonatal Sprague-Dawley rats were exposed to rectangular-wave pulsed ELF-EMF at four different frequencies (15?Hz, 50?Hz, 75?Hz and 100?Hz) and at a flux density of 2?mT. Intracellular calcium concentration ([Ca2+]i) was measured using Fura-2/AM and spectrofluorometry. Perfusion of cardiomyocytes with a high concentration of caffeine (10?mM) was carried out to verify the function of the cardiac Na+/Ca2+ exchanger (NCX) and the activity of sarco(endo)-plasmic reticulum Ca2+-ATPase (SERCA2a). The results showed that ELF-EMF enhanced the activities of NCX and SERCA2a, increased [Ca2+]i baseline level and frequency of calcium transients in cardiomyocytes and decreased the amplitude of calcium transients and calcium level in sarcoplasmic reticulum. These results indicated that ELF-EMF can regulate calcium-associated activities in cardiomyocytes. 相似文献
13.
Oxidative stress appears to be implicated in the pathogenesis of various diseases including hepatotoxicity. Although intracellular Ca2+ signals have been suggested to play a role in the oxidative damage of hepatocytes, the sources and effects of oxidant-induced intracellular Ca2+ increases are currently debatable. Thus, in this study we investigated the exact source and mechanism of oxidant-induced liver cell damage using HepG2 human hepatoma cells as a model liver cellular system. Treatment with 200 μM of tert-butyl hydroperoxide (tBOOH) induced a sustained increase in the level of intracellular reactive oxygen intermediates (ROI) and apoptosis, assessed by 2′,7′-dichlorofluorescein fluorescence and flow cytometry, respectively. Antioxidants, N-acetyl cysteine (NAC) or N,N′-diphenyl-p-phenylenediamine significantly inhibited both the ROI generation and apoptosis. In addition, tBOOH induced a slow and sustained increase in intracellular Ca2+ concentration, which was completely prevented by the antioxidants. An intracellular Ca2+ chelator, bis-(o-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid/cetoxymethyl ester significantly suppressed the tBOOH-induced apoptosis. These results imply that activation of an intracellular Ca2+ signal triggered by increased ROI may mediate the tBOOH-induced apoptosis. Both intracellular Ca2+ increase and induction of apoptosis were significantly inhibited by an extracellular Ca2+ chelator or Na+/Ca2+ exchanger blockers (bepridil and benzamil), whereas neither Ca2+ channel antagonists (verapamil and nifedipine) nor a nonselective cation channel blocker (flufenamic acid) had an effect. These results suggest that tBOOH may increase intracellular Ca2+ through the activation of reverse mode of Na+/Ca2+ exchanger. However, tBOOH decreased intracellular Na+ concentration, which was completely prevented by NAC. These results indicate that ROI generated by tBOOH may increase intracellular Ca2+ concentration by direct activation of the reverse mode of Na+/Ca>2+ exchanger, rather than indirect elevation of intracellular Na+ levels. Taken together, these results suggest that the oxidant, tBOOH induced apoptosis in human HepG2 cells and that intracellular Ca2+ may mediate this action of tBOOH. These results further suggest that Na+/Ca2+ exchanger may be a target for the management of oxidative hepatotoxicity. 相似文献
14.
Summary On the basis of a model presented in a previous paper (Hook and Hildebrand, 1979) the influence of external cation concentrations [K+]0, [Ca2+]0 and of membrane voltage Vm (i.e. the actual potential difference between the two membrane faces) on the locomotor behavior of Paramecium is theoretically analyzed. In an extended model system we discuss the negative feedback of intraciliary calcium [Ca2+]i on the excitability of the ciliary membrane. While a fast blocking of Ca channels is mediated by increased [Ca2+]i and accounts for the short duration of action potentials, a slow [Ca2+ ]i-dependent denaturation of channel molecules is assumed to determine excitability changes of Paramecium on a long time scale.It is emphasized that the duration of long-lasting ciliary reversal which reflects the excitability is not a direct function of the cation ratio Ju [K+]0/[Ca2+]
0
1/2
but rather of the membrane potential Vm.Introduction of negative surface charges can well explain why for a series of different [K+]0, [Ca2+]0 but constant Ja value the excitability is unchanged despite corresponding shifts in measured membrane potentials. 相似文献
15.
Mauro Salvi 《生物化学与生物物理学报:生物膜》2004,1661(2):113-124
Mammalian mitochondria are able to enhance Ca2+ accumulation in the presence of polyamines by activating the saturable systems of Ca2+ inward transport and buffering extramitochondrial Ca2+ concentrations to levels similar to those in the cytosol of resting cells. This effect renders them responsive to regulate free Ca2+ concentrations in the physioloical range. The mechanism involved is due to a rise in the affinity of the Ca2+ transport system, induced by polyamines, most probably exhibiting allosteric behaviour. The regulatory site of this mechanism is the so-called S1 binding site of polyamines, which operates in physiological conditions and is located in the energy well between the two peaks present in the energy profile of mitochondrial spermine transport. Spermine is bidirectionally transported across teh inner membrane by cycling, in which influx and efflux are driven by electrical and pH gradients, respectively. Most probably, polyamine affects the Ca2+ transport system when it acts from the outside-that is, in the direction of its uniporter channel, in order to reach the S1 site. Important physiological functions are related to activation of Ca2+ transport systems by polyamines and their interactions with the S1 site. These functions include a rise in the metabolic rate for energy supply and modulation of mitochondrial permeability transition induction, with consequent effects on the triggering of the apoptotic pathway. 相似文献
16.
This review will focus on the recent advance in the study of effect of transmembrane Ca2+ gradient on the function of membrane proteins. It consits of two parts: 1. Transmembrane Ca2+ gradient and sarcoplasmic reticulum Ca2+-ATPase; 2. Effect of transmembrane Ca2+ gradient on the components and coupling of cAMP signal transduction pathway. The results obtained indicate that a proper transmembrane Ca2+ gradient may play an important role in modulating the conformation and activity of SR Ca2+-ATPase and the function of membrane proteins involved in the cAMP signal transduction by mediating the physical state change of the membrane phospholipids.Abbreviations Cai
Ca2+ inside vesicles
- Ca0
Ca2+ outside vesicles
- SR
sarcoplasmic reticulum
- PC
phosphatidylcholine
- PS
phosphatidylserine
- PG
phosphatidylglycerol
- PE
phosphatidylethanolamine
- DPH
1,6-diphenyl-1,3,5-hexatriene
- n-AS
n-(9-anthroyloxy) fatty acids
- TMA-DPH
1-(4-trimethylammoniumphenyl)-6)-phenyl-1,3,5-hexatriene
- FCCP
carbonylcyanide-p-trifluoromethoxyphenylhydrazone
- -AR
-adrenergic receptors
- DHA
dihydroalprenolol
- AC
adenylate cyclase
- AC·Lca+–
higher Ca2+ inside vesicles
- AC·Lca– –
lower Ca2+ on both side of vesicles
- AC·Lca++
higher Ca2+ on both side of vesicles
- AC·Lca– +
higher Ca2+ outside vesicles
- cAMP
cyclic adenosine monophosphate
- Gs
stimulatory GTP-binding protein
- GTP
guanosine triposphate
- GTPS
guanosine 50-(3-thiotriphosphate) 相似文献
17.
Summary Ciliary motility was examined optically in tissue cultures from frog palate epithelium and frog's esophagus as a function of extracellular concentration of adenosine 5-triphosphate (ATP) and related compounds. The addition of micromolar concentration of ATP caused a strong enhancement of frequency and wave velocity in the direction of the effective stroke. Since adenosine 5-[, imido]-triphosphate (AMP-PNP), a nonhydrolyzable analog of ATP, produces the same effects, ATP hydrolysis is not required. The overall potency is ATP AMP-PNP>ADP adenosine>AMP. It is suggested that both the phosphate and the base moieties are involved in ATP binding.The enhancement of ciliary activity by extracellular ATP is dependent on the presence of extracellular Ca2+, which can be replaced by extracellular Mg2+. The effect of a number of potent inhibitors of the voltage-gated calcium channels on the stimulation of ciliary activity by ATP were examined. No effect was detected in the concentration range within which these agents are specific. On the other hand, quinidine, a potent inhibitor of K+ (calcium-dependent) channels, inhibits the effect of ATP.The following model is suggested: exogenous ATP interacts with a membrane receptor in the presence of Ca2+, a cascade of events occurs which mobilizes intracellular calcium, thereby increasing the cytosolic free Ca2+ concentration which consequently opens the calcium-activated K+ channels, which then leads to a change in membrane potential. The ciliary response to these changes is the enhancement of ciliary activity.This work was supported by a grant from the Fund for Basic Research administered by the Israel Academy of Science and Humanities. 相似文献
18.
Mitochondria exert a negative feedback on the propagation of intracellular Ca2+ waves in rat cortical astrocytes.
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We have used digital fluorescence imaging techniques to explore the interplay between mitochondrial Ca2+ uptake and physiological Ca2+ signaling in rat cortical astrocytes. A rise in cytosolic Ca2+ ([Ca2+]cyt), resulting from mobilization of ER Ca2+ stores was followed by a rise in mitochondrial Ca2+ ([Ca2+]m, monitored using rhod-2). Whereas [Ca2+]cyt recovered within approximately 1 min, the time to recovery for [Ca2+]m was approximately 30 min. Dissipating the mitochondrial membrane potential (Deltapsim, using the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxy-phenyl-hydrazone [FCCP] with oligomycin) prevented mitochondrial Ca2+ uptake and slowed the rate of decay of [Ca2+]cyt transients, suggesting that mitochondrial Ca2+ uptake plays a significant role in the clearance of physiological [Ca2+]cyt loads in astrocytes. Ca2+ signals in these cells initiated either by receptor-mediated ER Ca2+ release or mechanical stimulation often consisted of propagating waves (measured using fluo-3). In response to either stimulus, the wave traveled at a mean speed of 22.9 +/- 11.2 micrometer/s (n = 262). This was followed by a wave of mitochondrial depolarization (measured using tetramethylrhodamine ethyl ester [TMRE]), consistent with Ca2+ uptake into mitochondria as the Ca2+ wave traveled across the cell. Collapse of Deltapsim to prevent mitochondrial Ca2+ uptake significantly increased the rate of propagation of the Ca2+ waves by 50%. Taken together, these data suggest that cytosolic Ca2+ buffering by mitochondria provides a potent mechanism to regulate the localized spread of astrocytic Ca2+ signals. 相似文献
19.
Meyer zu Heringdorf D Liliom K Schaefer M Danneberg K Jaggar JH Tigyi G Jakobs KH 《FEBS letters》2003,554(3):443-449
Sphingosine-1-phosphate (S1P), the product of sphingosine kinase, activates several widely expressed G-protein-coupled receptors (GPCR). S1P might also play a role as second messenger, but this hypothesis has been challenged by recent findings. Here we demonstrate that intracellular S1P can mobilize Ca(2+) in intact cells independently of S1P-GPCR. Within seconds, S1P generated by the photolysis of caged S1P raised the intracellular free Ca(2+) concentration in HEK-293, SKNMC and HepG2 cells, in which the response to extracellularly applied S1P was either blocked or absent. Ca(2+) transients induced by photolysis of caged S1P were caused by Ca(2+) mobilization from thapsigargin-sensitive stores. These results provide direct evidence for a true intracellular action of S1P. 相似文献
20.
Gonda K Yoshida A Oami K Takahashi M 《Biochemical and biophysical research communications》2004,323(3):891-897
Voltage-gated Ca(2+) channels play a critical role in controlling Ca(2+) entry in various cells. Ciliary reversal in Paramecium depends on the Ca(2+) influx through voltage-gated Ca(2+) channels on the ciliary membrane. One of the voltage-gated Ca(2+) channel mutants in Paramecium caudatum, cnrC, neither produces Ca(2+) action potentials nor responds to any depolarizing stimuli. Here, we report that the cnrC(+) gene product is P. caudatum centrin (Pccentrin1p), a member of the Ca(2+)-binding EF-hand protein superfamily. The Pccentrin1p gene of cnrC was found to contain a single-base deletion, a mutation that caused the loss of the fourth EF-hand of Pccentrin1p. Moreover, the wild-type Ca(2+) channel function was impaired by Pccentrin1p gene silencing, leading to the loss of current-evoked Ca(2+) action potentials and stimulated ciliary reversal. These results demonstrate that Pccentrin1p is indispensable for the activity of the voltage-gated Ca(2+) channels that control ciliary reversal in Paramecium. 相似文献