共查询到20条相似文献,搜索用时 15 毫秒
1.
Ji J Muinuddin A Kang Y Diamant NE Gaisano HY 《Biochemical and biophysical research communications》2003,306(1):298-302
We recently reported that non-secretory gastrointestinal smooth muscle cells also possessed SNARE proteins, of which SNAP-25 regulated Ca(2+)-activated (K(Ca)) and delayed rectifier K(+) channels (K(V)). Voltage-gated, long lasting (L-type) calcium channels (L(Ca)) play an important role in excitation-contraction coupling of smooth muscle. Here, we show that SNAP-25 could also directly inhibit the L-type Ca(2+) channels in feline esophageal smooth muscle cells at the SNARE complex binding synprint site. SNARE proteins could therefore regulate additional cell actions other than membrane fusion and secretion, in particular, coordinated muscle membrane excitability and contraction, through their actions on membrane Ca(2+) and K(+) channels. 相似文献
2.
L-type Ca2+ channels in Ca2+ channelopathies 总被引:3,自引:0,他引:3
Striessnig J Hoda JC Koschak A Zaghetto F Müllner C Sinnegger-Brauns MJ Wild C Watschinger K Trockenbacher A Pelster G 《Biochemical and biophysical research communications》2004,322(4):1341-1346
Voltage-gated L-type Ca2+ channels (LTCCs) mediate depolarization-induced Ca2+ entry in electrically excitable cells, including muscle cells, neurons, and endocrine and sensory cells. In this review we summarize the role of LTCCs for human diseases caused by genetic Ca2+ channel defects (channelopathies). LTCC dysfunction can result from structural aberrations within pore-forming alpha1 subunits causing incomplete congenital stationary night blindness, malignant hyperthermia sensitivity or hypokalemic periodic paralysis. However, studies in mice revealed that LTCC dysfunction also contributes to neurological symptoms in Ca2+ channelopathies affecting non-LTCCs, such as Ca(v)2.1 alpha1 in tottering mice. Ca2+ channelopathies provide exciting molecular tools to elucidate the contribution of different LTCC isoforms to human diseases. 相似文献
3.
Various beta subunit isoforms stabilize different gating properties of voltage-gated L-type Ca(2+) channels. We therefore investigated the expression of Ca(2+) channel beta subunit isoforms in different smooth muscle types on the protein level by immunoblotting and immunoprecipitation employing beta subunit-selective sequence-directed antibodies. From the four known beta subunit isoforms only beta2 and beta3 were detected in porcine uterus, bovine trachea and bovine aorta membranes. Multiple immunoreactive beta2 bands were detected in a tissue-selective manner indicating structural heterogeneity of beta2. Immunoprecipitation of (+)-[(3)H]isradipine-prelabeled channels revealed that beta2 and beta3 participate in Ca(2+) channel formation in uterus and trachea, and beta3 in aortic smooth muscle. We conclude that beta2 and beta3 subunits form L-type Ca(2+) channels in smooth muscle tissues. This subunit heterogeneity may be important to fine-tune channel function. 相似文献
4.
Lim I Gibbons SJ Lyford GL Miller SM Strege PR Sarr MG Chatterjee S Szurszewski JH Shah VH Farrugia G 《American journal of physiology. Gastrointestinal and liver physiology》2005,288(1):G7-14
Carbon monoxide (CO) is increasingly recognized as a physiological messenger. CO is produced in the gastrointestinal tract with diverse functions, including regulation of gastrointestinal motility, interacting with nitric oxide (NO) to mediate neurotransmission. The aim of this study was to determine the effect of CO on the human intestinal L-type Ca(2+) channel expressed in HEK cells and in native cells using the patch-clamp technique. Extracellular solution contained 10 mM Ba(2+) as the charge carrier. Maximal peak Ba(2+) current (I(Ba)) was significantly increased by bath application of 0.2% CO to transfected HEK cells (18 +/- 3%). The NO donor S-nitroso-N-acetylpenicillamine also increased I(Ba), and CO (0.2%) increased NO production in transfected HEK cells. The CO-induced increase in I(Ba) was blocked when cells were pretreated with 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (10 microM) or inhibitors of NO synthase (NOS). The PKA inhibitor KT-5720 (0.5 microM) and milrinone (3 microM), a phosphodiesterase (PDE) III inhibitor, blocked the effect of CO on I(Ba). Similar effects were seen in freshly dissociated human intestinal smooth muscle cells. The data suggest that exogenous CO can activate native and heterologously expressed intestinal L-type Ca(2+) channels through a pathway that involves activation of NOS, increased NO, and cGMP levels, but not PKG. Rather, the pathway appears to involve PKA, partly by reducing cAMP breakdown through inhibition of PDE III. CO-induced NO production may explain the apparent discrepancy between the low affinity of guanylyl cyclase for CO and the robust cGMP production evoked by CO. 相似文献
5.
Ding Y Schwartz D Posner P Zhong J 《American journal of physiology. Cell physiology》2004,287(2):C413-C421
It has been suggested that L-type Ca2+ channels play an important role in cell swelling-induced vasoconstriction. However, there is no direct evidence that Ca2+ channels in vascular smooth muscle are modulated by cell swelling. We tested the hypothesis that L-type Ca2+ channels in rabbit portal vein myocytes are modulated by hypotonic cell swelling via protein kinase activation. Ba2+ currents (IBa) through L-type Ca2+ channels were recorded in smooth muscle cells freshly isolated from rabbit portal vein with the conventional whole cell patch-clamp technique. Superfusion of cells with hypotonic solution reversibly enhanced Ca2+ channel activity but did not alter the voltage-dependent characteristics of Ca2+ channels. Bath application of selective inhibitors of protein kinase C (PKC), Ro-318425 or Go-6983, prevented IBa enhancement by hypotonic swelling, whereas the specific protein kinase A (PKA) inhibitor KT-5720 had no effect. Bath application of phorbol 12,13-dibutyrate (PDBu) significantly increased IBa under isotonic conditions and prevented current stimulation by hypotonic swelling. However, PDBu did not have any effect on IBa when cells were first exposed to hypotonic solution. Furthermore, downregulation of endogenous PKC by overnight treatment of cells with PDBu prevented current enhancement by hypotonic swelling. These data suggest that hypotonic cell swelling can enhance Ca2+ channel activity in rabbit portal vein smooth muscle cells through activation of PKC. cell swelling; protein kinases; calcium current 相似文献
6.
V. A. Bouryi 《Neurophysiology》1998,30(4-5):301-304
Barium currents through ion channels formed by α1-subunit of L-type Ca2+ channel (I
α1) were recorded from cultured chinese hamster ovary (CHO) cells. The cells were stably transfected with either a cardiac or
a smooth muscle (SM) variant of α1-subunit. TheI
α1 in both cases exhibited similar fast voltage-dependent activation kinetics and slow apparent inactivation kinetics. With
10 mM Ba2+ in the bath solution,I
α1 was activated at potentials more positive than −40 mV, peaked between 0 and +10 mV, and reversed at about +50 mV. In addition
to slow apparent inactivation of inward current, both subunits provided an extremely slow voltage-dependent inactivation at
potentials more positive than −100 mV, with half-maximum inactivation at −43.4 mV for cardiac and −41.4 mV for SM α1-subunits.
The onset of inactivation as well as recovery from this process were within a time range of minutes. The voltage dependence
of steady-state inactivation could be fitted by the sum of two Boltzmann's equations with slope factors of about 12 mV and
5 mV. A less sloped component has its midpoints at −75.6 and −63.7 mV, and a steeper component has its midpoints at −42.8
and −37.7 mV for cardiac and SM α1-subunits, respectively. Relative contribution of the steeper component was higher in both
subunits (0.86 and 0.66 for cardiac and SM subunits, respectively). For comparison, the inactivation curves for 5-sec-long
conditioning prepulses could be fitted by single Boltzmann's distribution with a 20 mV more positive midpoint and a slope
factor of about 13 mV. In contrast to the steady-state inactivation curves, they showed considerable overlap with the steady-state
activation curve. Our results reflect functional consequences of known sequence differences between α1-subunits of the cardiac
and SM L-type Ca2+ channels and could be used in structural modeling of Ca2+ channel gating. In addition, they show that depolarization-induced window current has a transient nature and decays with
the development of extremely slow inactivation. This is the first demonstration that slow inactivation of the L-type Ca2+ channel is an intrinsic property of its α1-subunits. 相似文献
7.
8.
Block of single L-type Ca2+ channels in skeletal muscle fibers by aminoglycoside antibiotics 总被引:1,自引:1,他引:0
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《The Journal of general physiology》1996,107(3):421-432
The activity of single L-type Ca2+ channels was recorded from cell- attached patches on acutely isolated skeletal muscle fibers from the mouse. The experiments were concerned with the mechanism by which aminoglycoside antibiotics inhibit ion flow through the channel. Aminoglycosides produced discrete fluctuations in the single-channel current when added to the external solution. The blocking kinetics could be described as a simple bimolecular reaction between an aminoglycoside molecule and the open channel. The blocking rate was found to be increased when either the membrane potential was made more negative or the concentration of external permeant ion was reduced. Both of these effects are consistent with a blocking site that is located within the channel pore. Other features of block, however, were incompatible with a simple pore blocking mechanism. Hyperpolarization enhanced the rate of unblocking, even though an aminoglycoside molecule must dissociate from its binding site in the channel toward the external solution against the membrane field. Raising the external permeant ion concentration also enhanced the rate of unblocking. This latter finding suggests that aminglycoside affinity is modified by repulsive interactions that arise when the pore is simultaneously occupied by a permeant ion and an aminoglycoside molecule. 相似文献
9.
10.
目的:探讨大鼠结肠平滑肌细胞是否存在钙库操纵性通道(SOC)。方法:荧光探针Fura-2/AM标记细胞内游离Ca2+后,用荧光分光光度计检测毒胡萝卜素(thapsigargin)和咖啡因(caffeine)耗竭胞内钙库后激活的SOC通道对酶解分离的大鼠结肠平滑肌细胞[Ca2+]i的影响。结果:在无Ca2+缓冲液中,thapsigargin(1μmol/L)以及caf-feine(10 mmol/L)分别使[Ca2+]i由静息时(68.32±3.43)nmol/L升高至(240.85±12.65)nmol/L(、481.25±34.77)nmol/L,继之,向细胞外液中引入两种浓度的Ca2+(1.5 mmol/L和3.0 mmol/L),导致[Ca2+]i进一步升高,分别为(457.55±19.80)nmol/L、(1005.93±54.62)nmol/L;(643.88±34.65)nmol/L、(920.16±43.25)nmol/L。且上述升高效应对维拉帕米(verapamil,5μmol/L)以及KCl引起的细胞膜去极化不敏感,但可被La3+(1 mmol/L)抑制。结论:在酶解分离的大鼠结肠平滑肌细胞上,存在胞内钙库耗竭激活的SOC通道,为支持在电兴奋性细胞上存在库容性Ca2+内流提供了实验和理论依据。 相似文献
11.
It is well recognized that pathologically increased mechanical stretch plays a critical role in vascular remodeling during hypertension. However, how the stretch modulates the functions of ion channels of vascular smooth muscle cells (VSMCs) remains to be elucidated. Here, we demonstrated the effects of mechanical stretch on the activity of large conductance calcium, voltage-activated potassium (BK) and L-type Ca2+ channels. In comparison with 5% stretch (physiological), 15% stretch (pathological) upregulated the current density of L-type Ca2+ and BK channels as well as the frequency and amplitude of calcium oscillation in VSMCs. 15% stretch also increased the open probability and mean open time of the BK channel compared with 5% stretch. BK and L-type Ca2+ channels participated in the mechanical stretch-modulated calcium oscillation. Our results suggested that during hypertension, pathological stretch altered the activity of BK and L-type Ca2+ channels and manipulated the calcium oscillation of VSMCs. 相似文献
12.
Isaev D Solt K Gurtovaya O Reeves JP Shirokov R 《The Journal of general physiology》2004,123(5):555-571
Both intracellular calcium and transmembrane voltage cause inactivation, or spontaneous closure, of L-type (CaV1.2) calcium channels. Here we show that long-lasting elevations of intracellular calcium to the concentrations that are expected to be near an open channel (>/=100 microM) completely and reversibly blocked calcium current through L-type channels. Although charge movements associated with the opening (ON) motion of the channel's voltage sensor were not altered by high calcium, the closing (OFF) transition was impeded. In two-pulse experiments, the blockade of calcium current and the reduction of gating charge movements available for the second pulse developed in parallel during calcium load. The effect depended steeply on voltage and occurred only after a third of the total gating charge had moved. Based on that, we conclude that the calcium binding site is located either in the channel's central cavity behind the voltage-dependent gate, or it is formed de novo during depolarization through voltage-dependent rearrangements just preceding the opening of the gate. The reduction of the OFF charge was due to the negative shift in the voltage dependence of charge movement, as previously observed for voltage-dependent inactivation. Elevation of intracellular calcium concentration from approximately 0.1 to 100-300 microM sped up the conversion of the gating charge into the negatively distributed mode 10-100-fold. Since the "IQ-AA" mutant with disabled calcium/calmodulin regulation of inactivation was affected by intracellular calcium similarly to the wild-type, calcium/calmodulin binding to the "IQ" motif apparently is not involved in the observed changes of voltage-dependent gating. Although calcium influx through the wild-type open channels does not cause a detectable negative shift in the voltage dependence of their charge movement, the shift was readily observable in the Delta1733 carboxyl terminus deletion mutant, which produces fewer nonconducting channels. We propose that the opening movement of the voltage sensor exposes a novel calcium binding site that mediates inactivation. 相似文献
13.
《Phytomedicine》2013,21(14):1272-1279
This study aimed to investigate the effect of magnolol (5,5′-diallyl-2,2′-biphenyldiol) on contraction in distal colonic segments of rats and the underlying mechanisms. Colonic segments were mounted in organ baths for isometric force measurement. Whole-cell voltage-sensitive L-type Ca2+ currents were recorded on isolated single colonic smooth muscle cells using patch-clamp technique. The spontaneous contractions and acetylcholine (ACh)- and Bay K 8644-induced contractions were inhibited by magnolol (3–100 μM). In the presence of Bay K8644 (100 nM), magnolol (10–100 μM) inhibited the contraction induced by 10 μM ACh. By contrast, tetrodotoxin (100 nM) and Nώ-nitro-l-arginine methyl ester (l-NAME 100 μM) did not change the inhibitory effect of magnolol (10 μM). In addition, magnolol (3–100 μM) inhibited the L-type Ca2+ currents. The present results suggest that magnolol inhibits colonic smooth muscle contraction through downregulating L-type Ca2+ channel activity. 相似文献
14.
ATP inhibits smooth muscle Ca2(+)-activated K+ channels 总被引:3,自引:0,他引:3
C H Gelband S D Silberberg K Groschner C van Breemen 《Proceedings. Biological sciences / The Royal Society》1990,242(1303):23-28
There has been much recent interest in the roles played by smooth-muscle K+ channels in protecting cells against ischemic and anoxic insults and in therapeutic vaso- and bronchodilation (Buckingham 1990; Longmore & Weston 1990). A K+ channel, which is uniquely sensitive to cytoplasmic ATP (KATP), has been identified as a likely candidate for mediating these important functions (Standen et al. 1989). We now show, by using electrophysiological techniques in three different types of smooth muscle, that a large-conductance voltage and Ca2(+)-sensitive channel, otherwise indistinguishable from the the large-conductance Ca2(+)-activated K+ channel (BK channel), is also sensitive to cytoplasmic ATP and cromakalim. ATP, in a dose-dependent manner, decreased the probability of channel opening (Po) of rabbit aortic, rabbit tracheal and pig coronary artery BK channels with a Ki of 0.2-0.6 mM. Cromakalim, 10 microM, partially reversed the ATP induced inhibition and increased Po. Our observations raise the possibility that the ubiquitous BK channel may play a role during pathophysiological events. 相似文献
15.
Bowles DK Maddali KK Ganjam VK Rubin LJ Tharp DL Turk JR Heaps CL 《American journal of physiology. Heart and circulatory physiology》2004,287(5):H2091-H2098
Evidence indicates that gender and sex hormonal status influence cardiovascular physiology and pathophysiology. We recently demonstrated increased L-type voltage-gated Ca2+ current (ICa,L) in coronary arterial smooth muscle (CASM) of male compared with female swine. The promoter region of the L-type voltage-gated Ca2+ channel (VGCC) (Cav1.2) gene contains a hormone response element that is activated by testosterone. Thus the purpose of the present study was to determine whether endogenous testosterone regulates CASM ICa,L through regulation of VGCC expression and activity. Sexually mature male and female Yucatan swine (7-8 mo; 35-45 kg) were obtained from the breeder. Males were left intact (IM, n=8), castrated (CM, n=8), or castrated with testosterone replacement (CMT, n=8; 10 mg/day Androgel). Females remained gonad intact (n=8). In right coronary arteries, both Cav1.2 mRNA and protein were greater in IM compared with intact females. Cav1.2 mRNA and protein were reduced in CM compared with IM and restored in CMT. In isolated CASM, both peak and steady-state ICa were reduced in CM compared with IM and restored in CMT. In males, a linear relationship was found between serum testosterone levels and ICa. In vitro, both testosterone and the nonaromatizable androgen, dihydrotestosterone, increased Cav1.2 expression. Furthermore, this effect was blocked by the androgen receptor antagonist cyproterone. We conclude that endogenous testosterone is a primary regulator of Cav1.2 expression and activity in coronary arteries of males. 相似文献
16.
Small-conductance Ca2+-dependent K+ channels activated by ATP in murine colonic smooth muscle 总被引:3,自引:0,他引:3
Koh S. D.; Dick G. M.; Sanders K. M. 《American journal of physiology. Cell physiology》1997,273(6):C2010
The patch-clamptechnique was used to determine the ionic conductances activated by ATPin murine colonic smooth muscle cells. Extracellular ATP, UTP, and2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) increasedoutward currents in cells with amphotericin B-perforated patches. ATP(0.5-1 mM) did not affect whole cell currents of cells dialyzedwith solutions containing ethylene glycol-bis(-aminoethylether)-N,N,N',N'-tetraaceticacid. Apamin (3 × 107M) reduced the outward current activated by ATP by 32 ± 5%. Single channel recordings from cell-attached patches showed that ATP, UTP, and2-MeS-ATP increased the open probability of small-conductance, Ca2+-dependentK+ channels with a slopeconductance of 5.3 ± 0.02 pS. Caffeine (500 µM) enhanced the openprobability of the small-conductance K+ channels, and ATP had no effectafter caffeine. Pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid tetrasodium (PPADS,104 M), a nonselectiveP2 receptor antagonist, preventedthe increase in open probability caused by ATP and 2-MeS-ATP. PPADS hadno effect on the response to caffeine. ATP-induced hyperpolarization inthe murine colon may be mediated byP2y-induced release of Ca2+ from intracellular stores andactivation of the 5.3-pSCa2+-activatedK+ channels. 相似文献
17.
Over twenty years ago it was shown that depletion of the intracellular Ca2+ store in smooth muscle triggered a Ca2+ influx mechanism. The purpose of this review it to describe recent electrophysiological data which indicate that Ca2+ influx occurs through discrete ion channels in the plasmalemma of smooth muscle cells. The effect of external Ca2+ on the amplitude and reversal potential of whole-cell and single channel currents suggests that there are at least two, and probably more, distinct store-operated channels (SOCs) which have markedly different permeabilities to Ca2+ ions. Two activation mechanisms have been identified which involve Ca2+ influx factor and protein kinase C (PKC) activation via diacylglycerol. In addition, in rabbit portal vein cells there is evidence that stimulation of alpha-adrenoceptors can stimulate SOC opening via PKC in a store-independent manner. There is at present little knowledge on the molecular identity of SOCs but it has been proposed that TRPC1 may be a component of the functional channel. We also summarise the data showing that SOCs may be involved in contraction and cell proliferation of smooth muscle. Finally, we highlight the similarities and differences of SOCs and receptor-operated cation channels that are present in native rabbit portal vein myocytes. 相似文献
18.
Cribbs LL 《Cell calcium》2006,40(2):221-230
Vascular smooth muscle is a major constituent of the blood vessel wall, and its many functions depend on type and location of the vessel, developmental or pathological state, and environmental and chemical factors. Vascular smooth muscle cells (VSMCs) use calcium as a signal molecule for multiple functions. An important component of calcium signaling pathways is the entry of extracellular calcium via voltage-gated Ca2+ channels, which in vascular smooth muscle cells (VSMCs) are of two main types, the high voltage-activated (HVA) L-type and low voltage-activated (LVA) T-type channels. Whereas L-type channels function primarily to regulate Ca2+ entry for contraction, it is generally accepted that T-type Ca2+ channels do not contribute significantly to arterial vasoconstriction, with the possible exception of the renal microcirculation. T-type Ca2+ channels are also present in some veins that display spontaneous contractile activity, where they likely generate pacemaker activity. T-type Ca2+ channel expression has also been associated with normal and pathological proliferation of VSMCs, often stimulated by external cues in response to insult or injury. Expression of T-type channels has been linked to the G1 and S phases of the cell cycle, a period important for the signaling of gene expression necessary for cell growth, progression of the cell cycle and ultimately cell division. To better understand T-type Ca2+ channel functions in VSM, it will be necessary to develop new approaches that are specifically targeted to this class of Ca2+ channels and its individual members. 相似文献
19.
Large-conductance Ca2+-activated K+ channels in freshly dissociated smooth muscle cells 总被引:2,自引:0,他引:2
Freshly dissociated cells from the stomach muscularis of the toad Bufo marinus have been employed to carry out a systematic set of electrophysiological studies on the membrane properties of smooth muscle. The existence of Ca2+-activated K+ channels became apparent during the first studies under current clamp. In subsequent studies under voltage clamp, a Ca2+-activated. TEA-sensitive outward current was evident, and it was more than an order of magnitude larger than any other current observed in the cells. The channel responsible, at least in part, for this large outward current has been identified on the basis of single-channel records, and some of its main characteristics have been studied. It is similar in many respects to the large-conductance, Ca2+-activated K+ channel seen in other preparations. This channel has now been found in a considerable diversity of smooth muscle types. 相似文献
20.
Coassembly of big conductance Ca2+-activated K+ channels and L-type voltage-gated Ca2+ channels in rat brain 总被引:3,自引:0,他引:3
Based on electrophysiological studies, Ca(2+)-activated K(+) channels and voltage-gated Ca(2+) channels appear to be located in close proximity in neurons. Such colocalization would ensure selective and rapid activation of K(+) channels by local increases in the cytosolic calcium concentration. The nature of the apparent coupling is not known. In the present study we report a direct coassembly of big conductance Ca(2+)-activated K(+) channels (BK) and L-type voltage-gated Ca(2+) channels in rat brain. Saturation immunoprecipitation studies were performed on membranes labeled for BK channels and precipitated with antibodies against alpha(1C) and alpha(1D) L-type Ca(2+) channels. To confirm the specificity of the interaction, precipitation experiments were carried out also in reverse order. Also, additive precipitation was performed because alpha(1C) and alpha(1D) L-type Ca(2+) channels always refer to separate ion channel complexes. Finally, immunochemical studies showed a distinct but overlapping expression pattern of the two types of ion channels investigated. BK and L-type Ca(2+) channels were colocalized in various compartments throughout the rat brain. Taken together, these results demonstrate a direct coassembly of BK channels and L-type Ca(2+) channels in certain areas of the brain. 相似文献