共查询到20条相似文献,搜索用时 15 毫秒
1.
The ability of mitochondria to capture Ca2+ ions has important functional implications for cells, because mitochondria shape cellular Ca2+ signals by acting as a Ca2+ buffer and respond to Ca2+ elevations either by increasing the cell energy supply or by triggering the cell death program of apoptosis. A mitochondrial Ca2+ channel known as the uniporter drives the rapid and massive entry of Ca2+ ions into mitochondria. The uniporter operates at high, micromolar cytosolic Ca2+ concentrations that are only reached transiently in cells, near Ca2+ release channels. Mitochondria can also take up Ca2+ at low, nanomolar concentrations, but this high affinity mode of Ca2+ uptake is not well characterized. Recently, leucine-zipper-EF hand-containing transmembrane region (Letm1) was proposed to be an electrogenic 1:1 mitochondrial Ca2+/H+ antiporter that drives the uptake of Ca2+ into mitochondria at nanomolar cytosolic Ca2+ concentrations. In this article, we will review the properties of the Ca2+ import systems of mitochondria and discuss how Ca2+ uptake via an electrogenic 1:1 Ca2+/H+ antiport challenges our current thinking of the mitochondrial Ca2+ uptake mechanism. 相似文献
2.
Samantha J. Pitt Tim M. Funnell Mano Sitsapesan Elisa Venturi Katja Rietdorf Margarida Ruas A. Ganesan Rajendra Gosain Grant C. Churchill Michael X. Zhu John Parrington Antony Galione Rebecca Sitsapesan 《The Journal of biological chemistry》2010,285(45):35039-35046
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a molecule capable of initiating the release of intracellular Ca2+ required for many essential cellular processes. Recent evidence links two-pore channels (TPCs) with NAADP-induced release of Ca2+ from lysosome-like acidic organelles; however, there has been no direct demonstration that TPCs can act as NAADP-sensitive Ca2+ release channels. Controversial evidence also proposes ryanodine receptors as the primary target of NAADP. We show that TPC2, the major lysosomal targeted isoform, is a cation channel with selectivity for Ca2+ that will enable it to act as a Ca2+ release channel in the cellular environment. NAADP opens TPC2 channels in a concentration-dependent manner, binding to high affinity activation and low affinity inhibition sites. At the core of this process is the luminal environment of the channel. The sensitivity of TPC2 to NAADP is steeply dependent on the luminal [Ca2+] allowing extremely low levels of NAADP to open the channel. In parallel, luminal pH controls NAADP affinity for TPC2 by switching from reversible activation of TPC2 at low pH to irreversible activation at neutral pH. Further evidence earmarking TPCs as the likely pathway for NAADP-induced intracellular Ca2+ release is obtained from the use of Ned-19, the selective blocker of cellular NAADP-induced Ca2+ release. Ned-19 antagonizes NAADP-activation of TPC2 in a non-competitive manner at 1 μm but potentiates NAADP activation at nanomolar concentrations. This single-channel study provides a long awaited molecular basis for the peculiar mechanistic features of NAADP signaling and a framework for understanding how NAADP can mediate key physiological events. 相似文献
3.
Extracellular calcium is involved in stomatal movement through the regulation of water channels in broad bean 总被引:1,自引:0,他引:1
Involvement of extracellular Ca2+ in stomatal movement through the regulation of water channels was investigated in broad bean (Vicia faba L.). Leaf peels were first incubated to open stomata, and then transferred to buffers in the presence of different CaCl2 concentrations. Stomatal status was observed under magnification and stomatal aperture (pore width/length) was measured. Stomatal closure was significantly induced and aperture oscillation occurred at lower extracellular concentrations of calcium ([Ca2+]ext), while at higher concentrations, no significant change in stomatal aperture was observed, which was similar to the response recorded with HgCl2. Lower [Ca2+]ext-induced stomatal closure could be reversed using depolarizing buffer. It is suggested that lower [Ca2+]ext regulates water channels through an indirect way and at higher concentrations, extracellular Ca2+ is involved in regulating stomatal aperture by directly influencing water channels to retard aperture change. 相似文献
4.
Calcium signaling in myocytes is dependent on the cardiac ryanodine receptor (RyR2) calcium release channel and the calcium buffering protein in the sarcoplasmic reticulum, cardiac calsequestrin (CSQ2). The overall properties of CSQ2 and its regulation of RyR2 have not been explored in detail or directly compared with skeletal CSQ1 and its regulation of the skeletal RyR1, with physiological ionic strength and Ca2+ concentrations. We find that there are major differences between the two isoforms under these physiological conditions. Ca2+ binding to CSQ2 is 50% lower than to CSQ1. Only ~30% of CSQ2 is bound to cardiac junctional face membrane (JFM), compared with ~70% of CSQ1 and the ratio of CSQ2 to RyR2 is only 50% of the CSQ1/RyR1 ratio. Chemical crosslinking shows that CSQ2 is mostly monomer/dimer, while CSQ1 is mostly polymerized. In single channel lipid bilayer experiments, CSQ2 monomers and/or dimers increase the open probability of both RyR1 and RyR2 channels, while CSQ1 polymers decrease the activity of RyR1. We speculate that CSQ2 facilitates high rates of Ca2+ release through RyR2 during systole, while CSQ1 curtails RyR1 opening in response to a single action potential to maintain Ca2+ and allow repeated Ca2+ release and graded activation with increased stimulation frequency. 相似文献
5.
Steven H. Young 《Biochemical and biophysical research communications》2010,401(1):154-158
We examined crosstalk between the insulin receptor and G protein-coupled receptor (GPCR) signaling pathways in individual human pancreatic cancer PANC-1 cells. Treatment of cells with insulin (10 ng/ml) for 5 min markedly enhanced the proportion of cells that display an increase in intracellular [Ca2+] induced by picomolar concentrations of the GPCR agonist neurotensin. Interestingly, insulin increased the proportion of a subpopulation of cells that exhibit intracellular [Ca2+] oscillations in response to neurotensin at concentrations as low as 50-200 pM. Insulin enhanced GPCR-induced Ca2+ signaling in a time- and dose-dependent manner; a marked potentiation was obtained after an exposure to a concentration of 10 ng/ml for 5 min. Treatment with the mTORC1 inhibitor rapamycin abrogated the increase in GPCR-induced [Ca2+]i oscillations produced by insulin. Our results identify a novel aspect in the crosstalk between insulin receptor and GPCR signaling systems in pancreatic cancer cells, namely that insulin increases the number of [Ca2+]i oscillating cells induced by physiological concentrations of GPCR agonists through an mTORC1-dependent pathway. 相似文献
6.
Previous studies showed that Ca2+ induced monomer to active dimer interconversion of a mitochondrial ATPase inhibitor protein from bovine heart or rat skeletal muscle (Yamada, E.W., Huzel, N.J. and Dickison, J.C. (1981) J. Biol. Chem.
, 10203–10207). Initial equilibrium dialysis measurements of Ca2+ binding showed that this unique protein possesses three binding sites of high affinity with a maximum of one mol of Ca2+ bound/mol of protein monomer. Magnesium (1 mM) did not affect the first association constant but increased the second and third by about 1.2 and 1.5 fold, respectively. That the apparent association constants varied with concentration of protein monomer was in agreement with the self-associating nature of the protein. Scatchard plots at three concentrations of protein intersected at a molar ratio of about 0.5 (Ca2+/monomer). Ka1 and Ka2 values of 4.2 μM and 12.1 μM, respectively, were estimated by extrapolation of apparent constants to infinite dilution of protein. Ka3 (51.3 μM) was estimated by extrapolation of double reciprocal plots of apparent constants versus protein concentration to infinite levels of protein. A model for Ca2+ binding by this self-associating protein is described. Trifluoperazine had no effect on the activity of the inhibitor protein from either tissue. 相似文献
7.
Reactive oxygen species (ROS) are increasingly recognized as second messengers in many cellular processes. While high concentrations of oxidants damage proteins, lipids and DNA, ultimately resulting in cell death, selective and reversible oxidation of key residues in proteins is a physiological mechanism that can transiently alter their activity and function. Defects in ROS producing enzymes cause disturbed immune response and disease.Changes in the intracellular free Ca2+ concentration are key triggers for diverse cellular functions. Ca2+ homeostasis thus needs to be precisely tuned by channels, pumps, transporters and cellular buffering systems. Alterations of these key regulatory proteins by reversible or irreversible oxidation alter the physiological outcome following cell stimulation. It is therefore necessary to understand which proteins are regulated and if this regulation is relevant in a physiological- and/or pathophysiological context. Because ROS are inherently difficult to identify and to measure, we first review basic oxygen redox chemistry and methods of ROS detection with special emphasis on electron paramagnetic resonance (EPR) spectroscopy. We then focus on the present knowledge of redox regulation of Ca2+ permeable ion channels such as voltage-gated (CaV) Ca2+ channels, transient receptor potential (TRP) channels and Orai channels. 相似文献
8.
9.
We have previously characterized the “RCA” channel (root Ca2+ channel), a voltage-dependent, Ca2+-permeable channel found in plasma membrane-enriched vesicles from wheat roots incorporated into artificial planar lipid bilayers.
Earlier work indicated that this channel was insensitive to 1,4-dihydropyridines (DHPs, such as nifedipine and 202–791). However,
the present study shows that this channel is sensitive to DHPs, but only with submillimolar Ca2+, when the probability of channel opening is reduced, with flickery closures becoming increasingly evident as Ca2+ activity decreases. Under these ionic conditions, addition of nanomolar concentrations of (+) 202–791 or nifedipine caused
an increase in both the probability of channel opening and the unitary conductance. It is proposed that there is a competitive
interaction between Ca2+ and DHPs at one of the Ca2+-binding sites involved in Ca2+ permeation and that binding of a DHP to one of the Ca2+-permeation sites facilitates movement of other calcium ions through the channel. The present study shows that higher plant
Ca2+-permeable channels can be greatly affected by very low concentrations of DHPs and that channel sensitivity may vary with
the ionic conditions of the experiment. The results also indicate interesting structural and functional differences between
plant and animal Ca2+-permeable channels. 相似文献
10.
We investigated the effects of changes in luminal [Ca2+] on the gating of native andpurified sheep cardiac sarcoplasmic reticulum (SR) Ca2+-release channels reconstituted intoplanar phospholipid bilayers. The open probability (P
o
)of channels activated solely by cytosolic Ca2+ was greater at positive than negative holding potentials. Channels activatedsolely by 10 m cytosolic Ca2+ exhibited no change in steady-stateP
o
or in the relationship betweenP
o
and voltage when the luminal[Ca2+] was increased from nanomolar to millimolar concentrations. In the absence of activating concentrationsof cytosolic Ca2+, the channel can be activated by the phosphodiesterase inhibitor sulmazole (AR-L 115BS). However, cytosolicCa2+-independent activation of the channel by sulmazole requires luminal Ca2+. In the presence ofsulmazole, at picomolar luminal [Ca2+] the channel remains completely closed. Increasing the luminal [Ca2+]to millimolar levels markedly increases the P
o
via an increase in theduration of open events. The P
o
and duration of the sulmazole-activated, luminalCa2+-dependent channel openings are voltage dependent. In the presence of micromolar luminal Ca2+, theP
o
and duration of sulmazole-activated openings are greater atnegative voltages. However, at millimolar luminal [Ca2+], long openings are also observed at positive voltages and theP
o
appears to be similar at positive and negative voltages. Our findings indicate thatthe regulation of channel gating by luminal Ca2+ depends on the mechanism of channel activation.We would like to thank Dr Allan Lindsay for the preparation of the purified SR Ca2+-release channels. This work was supported by the British Heart Foundation. 相似文献
11.
Human neonatal skin fibroblasts plated sparsely in MCDB 105 traversed a complete cell cycle in the absense of serum or serum-derived proteins. Addition of pure PDGF did not significantly increase entrance into S phase as revealed by 3H-thymidine labeling index or clonal growth on palladium islands. In subphysiologic Ca2+ concentrations or in the presence of a calmodulin inhibitor, W7, proliferation in the absence of growth factors ceased and PDGF became mitogenic. In contrast, confluent fibroblast cultures were stimulated by PDGF in physiologic Ca2+ concentrations. This was also the case with sparse adult skin fibroblast cultures while a fetal strain entered S in the absence of PDGF even in low extracellular Ca2+ concentrations. EGF gave similar results as PDGF in all experiments performed. This proposes a similar role for the two growth factors in the cell cycle. However, a difference in the mechanisms of action of PDGF and EGF is indicated by the fact that PDGF and EGF were additive at optimal concentrations when maximal growth response by a single growth factor was restricted by a subphysiologic extracellular Ca2+ concentration. 相似文献
12.
Cell adhesion molecules (CAMs) play indispensable roles in the developing and mature brain by regulating neuronal migration and differentiation, neurite outgrowth, axonal fasciculation, synapse formation and synaptic plasticity. CAM-mediated changes in neuronal behavior depend on a number of intracellular signaling cascades including changes in various second messengers, among which CAM-dependent changes in intracellular Ca2+ levels play a prominent role. Ca2+ is an essential secondary intracellular signaling molecule that regulates fundamental cellular functions in various cell types, including neurons. We present a systematic review of the studies reporting changes in intracellular Ca2+ levels in response to activation of the immunoglobulin superfamily CAMs, cadherins and integrins in neurons. We also analyze current experimental evidence on the Ca2+ sources and channels involved in intracellular Ca2+ increases mediated by CAMs of these families, and systematically review the role of the voltage-dependent Ca2+ channels (VDCCs) in neurite outgrowth induced by activation of these CAMs. Molecular mechanisms linking CAMs to VDCCs and intracellular Ca2+ stores in neurons are discussed. 相似文献
13.
Ćelić AS Petri ET Benbow J Hodsdon ME Ehrlich BE Boggon TJ 《The Journal of biological chemistry》2012,287(21):17232-17240
Polycystin-2 (PC2) is a Ca2+-permeable transient receptor potential channel activated and regulated by changes in cytoplasmic Ca2+. PC2 mutations are responsible for ∼15% of autosomal dominant polycystic kidney disease. Although the C-terminal cytoplasmic tail of PC2 has been shown to contain a Ca2+-binding EF-hand domain, the molecular basis of PC2 channel gating by Ca2+ remains unknown. We propose that the PC2 EF-hand is a Ca2+ sensor required for channel gating. Consistent with this, Ca2+ binding causes a dramatic decrease in the radius of gyration (Rg) of the PC2 EF-hand by small angle x-ray scattering and significant conformational changes by NMR. Furthermore, increasing Ca2+ concentrations cause the C-terminal cytoplasmic tail to transition from a mixture of extended oligomers to a single compact dimer by analytical ultracentrifugation, coupled with a >30 Å decrease in maximum interatomic distance (Dmax) by small angle x-ray scattering. Mutant PC2 channels unable to bind Ca2+ via the EF-hand are inactive in single-channel planar lipid bilayers and inhibit Ca2+ release from ER stores upon overexpression in cells, suggesting dominant negative properties. Our results support a model where PC2 channels are gated by discrete conformational changes in the C-terminal cytoplasmic tail in response to changes in cytoplasmic Ca2+ levels. These properties of PC2 are lost in autosomal dominant polycystic kidney disease, emphasizing the importance of PC2 to kidney cell function. We speculate that PC2 and the Ca2+-dependent transient receptor potential channels in general are regulated by similar conformational changes in their cytoplasmic domains that are propagated to the channel pore. 相似文献
14.
Haleli Sharir Anna Zinger Andrey Nevo Israel Sekler Michal Hershfinkel 《The Journal of biological chemistry》2010,285(34):26097-26106
A role for Zn2+ in accelerating wound healing is established, yet, the signaling pathways linking Zn2+ to tissue repair are not well known. We show that in the human HaCaT keratinocytes extracellular Zn2+ induces a metabotropic Ca2+ response that is abolished by silencing the expression of the G-protein-coupled receptor GPR39, suggesting that this Zn2+-sensing receptor, ZnR, is mediating the response. Keratinocytic-ZnR signaling is highly selective for Zn2+ and can be triggered by nanomolar concentrations of this ion. Interestingly, Zn2+ was also released following cellular injury, as monitored by a specific non-permeable fluorescent Zn2+ probe, ZnAF-2. Chelation of Zn2+ and scavenging of ATP from conditioned medium, collected from injured epithelial cultures, was sufficient to eliminate the metabotropic Ca2+ signaling. The signaling triggered by Zn2+, via ZnR, or by ATP further activated MAP kinase and induced up-regulation of the sodium/proton exchanger NHE1 activity. Finally, activation of ZnR/GPR39 signaling or application of ATP enhanced keratinocytes scratch closure in an in vitro model. Thus our results indicate that extracellular Zn2+, which is either applied or released following injury, activates ZnR/GPR39 to promote signaling leading to epithelial repair. 相似文献
15.
Yagodin Sergey Holtzclaw Lynne A. Russell James T. 《Molecular and cellular biochemistry》1995,149(1):137-144
We have analysed Ca2+ waves induced by norepinephrine in rat cortical astrocytes in primary culture using fluorescent indicators fura-2 or fluo-3. The temporal pattern of the average [Ca2+]i responses were heterogeneous from cell to cell and most cells showed an oscillatory response at concentrations of agonist around EC50 (200 nM). Upon receptor activation, [Ca2+]i signals originated from a single cellular locus and propagated throughout the cell as a wave. Wave propagation was supported by specialized regenerative calcium release loci along the length of the cell. The periods of oscillations, amplitudes, and the rates of [Ca2+]i rise of these subcellular oscillators differ from each other. These intrinsic kinetic properties of the regenerative loci support local waves when stimulation is continued over long periods of time. The presence of local waves at specific, invariant cellular sites and their inherent kinetic properties provide for the unique and reproducible pattern of response seen in a given cell. We hypothesize that these loci are local specializations in the endoplasmic reticulum where the magnitude of the regenerative Ca2+ release is higher than other regions of the cell. Removal of extracellular Ca2+ or blockade of Ca2+ channels by inorganic cations (Cd2+ and Ni2+) during stimulation of adrenergic receptors alter the sustained plateau component of the [Ca2+]i response. In the absence of Ca2+ release, due to store depletion with thapsigargin, agonist occupation alone does not induce Ca2+ influx in astrocytes. This finding suggests that, under these conditions, receptor-operated Ca2+ entry is not operative. Furthermore, our experiments provide evidence for local Ca2+ oscillations in cells which can support both wave propagation as well as spatially discrete Ca2+ signalling. 相似文献
16.
Previous studies showed that Ca2+ induced monomer to active dimer interconversion of a mitochondrial ATPase inhibitor protein from bovine heart or rat skeletal muscle (Yamada, E.W., Huzel, N.J. and Dickison, J.C. (1981) J. Biol. Chem. , 10203–10207). Initial equilibrium dialysis measurements of Ca2+ binding showed that this unique protein possesses three binding sites of high affinity with a maximum of one mol of Ca2+ bound/mol of protein monomer. Magnesium (1 mM) did not affect the first association constant but increased the second and third by about 1.2 and 1.5 fold, respectively. That the apparent association constants varied with concentration of protein monomer was in agreement with the self-associating nature of the protein. Scatchard plots at three concentrations of protein intersected at a molar ratio of about 0.5 (). Ka1 and Ka2 values of 4.2 μM and 12.1 μM, respectively, were estimated by extrapolation of apparent constants to infinite dilution of protein. Ka3 (51.3 μM) was estimated by extrapolation of double reciprocal plots of apparent constants versus protein concentration to infinite levels of protein. A model for Ca2+ binding by this self-associating protein is described. Trifluoperazine had no effect on the activity of the inhibitor protein from either tissue. 相似文献
17.
Randriamampita C Trautmann A 《Biology of the cell / under the auspices of the European Cell Biology Organization》2004,96(1):69-78
Abstract Interaction between a T cell and an antigen‐presenting cell leads to the rapid formation of an immunological synapse allowing antigen detection by the T cell and the development of an immune response. Antigen detection triggers various cellular responses including a modest but sustained T cell Ca2+ increase. In this review are discussed a series of related questions. What are the various molecular events by which a T cell Ca2+ response can be triggered in the immunological synapse by a very small amount of antigen ? How is Ca2+ released from intracellular stores and how can these stores remain empty for hours ? Through which channels does Ca2+ influx takes place, and how is Ca2+ influx coupled to Ca2+ release from intracellular stores ? What are the main immediate and indirect cellular targets of the Ca2+ increase ? 相似文献
18.
Peter W. Marks Benjamin A. Kruskal Frederick R. Maxfield 《Journal of cellular physiology》1988,136(3):519-525
The calcium-sensitive fluorescent indicator fura-2 and a microscope equipped for rapidly changing excitation wavelengths were used to look at the effects of growth factors on cytosolic free calcium ([Ca2+]i,) in NRK-49F cells. In these cells bradykinin induced a rapid increase in [Ca2+]i, which generally decayed to near basal [Ca2+]i within 3 minutes. The initial rise in [Ca2+]i in response to bradykinin was relatively independent of extracellular calcium; however, the decay to basal [Ca2+]i was more rapid in the absence of extracellular calcium. Measurements made on individual cells showed a heterogeneity in the response to bradykinin. Epidermal growth factor (EGF) had no effect on [Ca2+]i in NRK-49F cells when added alone in the presence of extracellular calcium. Simultaneous addition of bradykinin and EGF produced a more prolonged increase in [Ca2+]i than bradykinin alone. The prolongation was dependent on the presence of extracellular calcium and did not occur in its absence. Transient increases in [Ca2+]i occurring after the initial peak were occasionally seen in these cells. Our results indicate that there is rapid interaction between the signaling mechanisms for bradykinin and EGF. When this occurs, one effect is the transport of calcium into the cell from the extracellular environment, causing a more prolonged rise in [Ca2+]i. This effect occurs within 1 minute after combined addition of bradykinin and EGF. 相似文献
20.
Calcium Uptake and Catecholamine Secretion by Cultured Bovine Adrenal Medulla Cells 总被引:20,自引:8,他引:12
Daniel L. Kilpatrick Ruta J. Slepetis James J. Corcoran Norman Kirshner 《Journal of neurochemistry》1982,38(2):427-435
Abstract: The uptake of 45Ca2+ and secretion of catecholamines by primary cultures of adrenal medulla cells were studied. Nicotine, veratridine, potassium, and Ionomycin stimulate both the accumulation of 45Ca2+ and the secretion of catecholamines. Nicotinic antagonists block 45Ca2+ uptake induced by nicotine, tetrodotoxin blocks 45Ca2+ uptake induced by veratridine, and D600 blocks uptake induced by K+, nicotine, and veratridine, but not 45Ca2+ uptake or secretion induced by Ionomycin. The EC50 for nicotine is 3 μm for catecholamine secretion and 10 μm for 45Ca2+ uptake, while the EC50S for veratridinestimulated uptake and secretion are approximately the same (75 μm ). Kinetic studies show that the uptake of Ca2+ is rapid and appears to precede the secretion of catecholamines, and that the rate of uptake declines rapidly. The uptake of 45Ca2+ and secretion of catecholamines stimulated by veratridine and 50 mm -K+ show saturation kinetics with respect to external calcium concentrations at about 2 mm . On the other hand, the uptake of 45 Ca2+ stimulated by nicotine does not become saturated at external calcium concentrations of 10 mm although the secretion of catecholamines reaches a maximum at external calcium concentrations of 2 mm . The data suggest that depolarizing agents such as veratridine and 50 mm -K+ stimulate 45Ca2+ entry through voltage-sensitive calcium channels, while nicotinic agonists stimulate calcium entry through the acetylcholine receptor ion channels as well as through voltage-sensitive calcium channels. 相似文献