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1.
Calcium (Ca 2+) entry from the extra-cellular space into the cytoplasm through voltage-dependent Ca 2+ channels, specifically dipyridamole (DHP) sensitive ones (L-type), control a variety of biological processes, including excitation-contraction coupling in vascular and GI muscle cells. It has also been proposed that these channels may control esophageal contractility. However, DHP-sensitive Ca 2+ channels in esophagus have not been well characterized biochemically. Thus, it is not known if these channels are similar in number or affinity to those in vascular or neural tissues — organs for which clinical use of calcium channel blockers has been successful. Thus, the purpose of this study was to identify and characterize DHP-sensitive calcium channels in esophagus and compare them to vascular, neural, and other GI tissues. Methods — We carried out in vitro receptor binding assays on lower esophageal muscle homogenates, gastric and intestinal and colonic homogenates, and aortic muscle homogenates from ca; and on brain homogenates from rat. We used a radio-labeled dihydropyridine derivative [ 3H]nitrendipine, to label these sites and co-administration of unlabeled nimodipine to define specific binding. Results — As expected, ligand binding to L-type Ca 2+ channels in aortic vascular smooth muscle and brain was readily detectable: brain, Bmax = 252 fmol/mg protein, Kd = 0.88 nM; aorta, Bmax = 326 fmol/mg protein, Kd = 0.84 nM. For esophagus (Bmax = 97; Kd = 0.73) and for other GI tissues, using the same assay conditions, we detected a smaller signal, suggesting that L-type Ca 2+ channels are present in lower quantities. Conclusion — L-type Ca 2+ channel are present in esophagus and in other GI muscles, their affinity is similar, but their density is relatively sparse. These findings are consistent with the relatively limited success that has been experienced clinically in the use of calcium channel blockers for treatment of esophageal dysmotility. 相似文献
2.
为了探明褪黑素(MT)和钙离子(Ca 2+)在调控植物耐热性中是否存在互作关系,以黄瓜幼苗为试材,分析了内源MT和Ca 2+对高温胁迫的响应;并通过叶面喷施100 μmol·L -1 MT、10 mmol·L -1 CaCl 2、3 mmol·L -1乙二醇二乙醚二胺四乙酸(EGTA,Ca 2+螯合剂)+100 μmol·L -1 MT、0.05 mmol·L -1氯丙嗪(钙调素拮抗剂,CPZ)+100 μmol·L -1 MT、100 μmol·L -1氯苯丙氨酸(p-CPA,MT合成抑制剂)+10 mmol·L -1 CaCl 2和去离子水(H 2O),研究高温下(42/32 ℃)外源MT和Ca 2+对黄瓜幼苗活性氧积累、抗氧化系统及热激转录因子( HSF)和热激蛋白( HSPs)等的影响。结果表明: 黄瓜幼苗内源MT和Ca 2+均受高温胁迫诱导;外源MT可上调常温下钙调素蛋白( CaM)、钙依赖蛋白激酶( CDPK5)、钙调磷酸酶B类蛋白( CBL3)、CBL结合蛋白激酶( CIPK2)mRNA表达;CaCl 2处理的MT合成关键基因色氨酸脱羧酶( TDC)、5-羟色胺-N-乙酰转移酶( SNAT)和N-乙酰-5-羟色胺甲基转移酶( ASMT)水平也显著升高,MT含量快速增加。MT和CaCl 2可显著增强高温下黄瓜的抗氧化能力,减少活性氧(ROS)积累,同时上调 HSF7、 HSP70.1和 HSP70.11 mRNA表达,从而减轻高温胁迫引起的过氧化伤害,植株热害症状明显减轻,热害指数和电解质渗漏率显著降低。加入EGTA和CPZ后,MT对黄瓜幼苗抗氧化能力和热激蛋白表达的促进效应明显减弱,Ca 2+对高温下黄瓜幼苗过氧化伤害的缓解效应也被p-CPA逆转。可见,MT和Ca 2+均可诱导黄瓜幼苗的耐热性,二者在热胁迫信号转导过程中存在互作关系。 相似文献
3.
The adjustment of Ca 2+ entry in cardiac cells is critical to the generation of the force necessary for the myocardium to meet the physiological needs of the body. In this review, we present the concept that Ca 2+ can promote its own entry through Ca 2+ channels by different mechanisms. We refer to it under the general term of ‘Ca2+-induced Ca2+ entry’ (CICE). We review short-term mechanisms (usually termed facilitation) that involve a stimulating effect of Ca 2+ on the L-type Ca 2+ current ( ICa-L) amplitude (positive staircase) or a lessening of Ca 2+-dependent inactivation of ICa-L. This latter effect is related to the amount of Ca 2+ released by ryanodine receptors (RyR2) of the sarcoplasmic reticulum (SR). Both effects are involved in the control of action potential (AP) duration. We also describe a long-term mechanism based on Ca 2+-dependent down-regulation of the Kv4.2 gene controlling functional expression of the repolarizing transient outward K + current ( Ito) and, thereby, AP duration. This mechanism, which might occur very early during the onset of hypertrophy, enhances Ca 2+ entry by maintaining Ca 2+ channel activation during prolonged AP. Both Ca 2+-dependent facilitation and Ca 2+-dependent down-regulation of Ito expression favour AP prolongation and, thereby, promote sustained voltage-gated Ca 2+ entry used to enhance excitation–contraction (EC) coupling (with no change in the density of Ca 2+ channels per se). These self-maintaining mechanisms of Ca 2+ entry have significant functions in remodelling Ca 2+ signalling during the cardiac AP. They might support a prominent role of Ca 2+ channels in the establishment and progression of abnormal Ca 2+ signalling during cardiac hypertrophy and congestive heart failure. 相似文献
4.
The role of Ca 2+ in glycerol dissimilation under hypoosmotic stress in the halotolerant alga Dunaliella tertiolecta was investigated using a pharmacological approach. A stretch-activated Ca 2+ channel blocker, GdCl 3, inhibited glycerol dissimilation under hypoosmotic stress. However, addition of voltage-dependent Ca 2+ channel blockers and inhibitors of mitochondrial and endoplasmic reticulum Ca 2+ channels did not affect the glycerol dissimilation under hypoosmotic stress. The results of the present study suggest that the influx of Ca 2+ from the extracellular space via the stretch-activated Ca 2+ channels localized in the plasma membrane is required for the transduction of osmotic signal of D. tertiolecta. 相似文献
5.
Calmodulin binding to a membrane fraction enriched in synaptic plasma membranes of sheep brain cells was investigated with [ 125I]calmodulin. Calmodulin binding to these membranes is Ca 2+-dependent with a half maximal saturation at the pCa value of about 5.5. The binding is reduced by replacing Ca 2+ with Mg 2+, but it is significantly enhanced when both cations are present in the medium. Cation-dependent binding is specific and saturable with an apparent KD of about 47–50 nM and a maximal capacity of about 4 pmol mg −1 protein. The results indicate that synaptic plasma membranes isolated from sheep brain cells interact with calmodulin in a Ca 2+-dependent, Mg 2+-facilitated manner. 相似文献
7.
In this study we seek to elucidate the interaction of capsaicin with the calmodulin mediated signal pathways in macrophages, by comparing its action on macrophage functions with a known calmodulin antagonist, fluphenazine. Kinetics of capsaicin uptake by macrophages (10 3 cells) revealed that a maximum of 200 μM capsaicin was taken up within 10 min. Ca 2+ ionophore triggered generation of superoxide anion and hydrogen peroxide by macrophages was inhibited in a dose-dependent manner by fluphenazine (IC 50, 20 μM and 12 μM, respectively) and also by capsaicin (IC 50, 30 μM and 9 μM, respectively), suggesting an involvement of calmodulin in the regulation of NADPH oxidase. In vitro both fluphenazine and capsaicin inhibited Ca 2+-Mg 2+ ATPase and cAMP-phosphodiesterase from macrophages and this inhibition was reversed by exogenous addition of calmodulin. Fluorescence studies revealed a direct Ca 2+ dependent interaction of capsaicin with calmodulin. From these results we suggest that capsaicin acts via calmodulin to inhibit stimulus-induced macrophage oxidative burst and also that calmodulin regulates the oxidative burst in macrophages. 相似文献
8.
Protein phosphorylation in vitro was investigated in guard cells from Vicia faba. A number of proteins with apparent molecular masses of 72, 67, 57, 52, 49, 44, 37, and 26 kDa were phosphorylated when guard-cell extract was incubated with [γ- 32P]ATP under Ca 2+-free conditions. In the presence of Ca 2+ at 1 μM, several proteins with apparent molecular masses of 125, 83, 41, 31, and 25 kDa were newly phosphorylated. These Ca 2+-dependent protein phosphorylations were suppressed by (8 R*,9 S*,11 S*)-(−)-9-hydroxy-9-methoxycarbonyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1 H,8 H,11 H-2,7b,11a- triazadibenzo[ a,g]cycloocta[ cde]trinden-1-one (K-252a), a wide-range inhibitor of protein kinases, suggesting that the protein phosphorylations were mediated by protein kinases. Several proteins were phosphorylated in vitro in mesophyll extract from Vicia. In contrast to guard cells, there was no detectable Ca 2+-dependent protein phosphorylation in mesophyll cells. 1-(5-Indonaphthalene-1-sulfonyl)-1 H-hexahydro-1,4-diazepine (ML-7), an inhibitor of myosin light chain kinase (MLCK), and an antagonist of calmodulin (CaM), N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), inhibited Ca 2+-dependent phosphorylation of 41- and 25-kDa proteins in guard cells. Fractionation experiments revealed that the Ca 2+-dependent phosphorylated proteins with molecular masses of 41 and 25 kDa were present in the mitochondria, and the 125- and 31-kDa proteins in the cytosol. These results suggest that Ca 2+-dependent protein phosphorylation occurs markedly in guard cells, and that Ca 2+-dependent phosphorylation of 41- and 25-kDa proteins may be catalyzed by MLCK or MLCK-like protein kinase in guard cells. 相似文献
9.
Much of the cholesterol used in steroid synthesis is stored in lipid droplets in the cytoplasm of steroid-forming cells. The cholesterol ester in these droplets is transported to the inner mitochondrial membrane where it enters the pathway to steroid hormones as free cholesterol—the substrate for the first enzyme, namely P450 scc. It has been shown that this transport process governs the rate of steroid synthesis and is specifically stimulated by ACTH and its second messenger. The stimulating influence of ACTH on cholesterol transport is inhibited by cytochalasins, by monospecific anti-actin and by DNase I demonstrating that the steroidogenic cell must possess a pool of monomeric actin available for polymerization to F actin if it is to respond to ACTH and cyclic AMP. It has been shown that the two structures involved in cholesterol transport (droplets and mitochondria) are both bound to vimentin intermediate filaments in adrenal and Leydig cells. In addition these filaments are closely associated with the circumferential actomyosin ring in which they are crosslinked by actin microfilaments. In permeabilized adrenal cells Ca 2+/calmodulin phosphorylates vimentin and this change is known to disrupt intermediate filaments and to cause contraction of actomyosin by phosphorylating myosin light chain kinase. Ca 2+/calmodulin stimulated cholesterol transport and steroid synthesis and causes rounding of the responding cells by contraction of the actomyosin, if ATP is also added at the same time. Other agents that disrupt intermediate filaments include anti-vimentin plus ATP in permeabilized cells which also results in rounding of the cell. Acrylamide exerts a similar effect in intact adrenal cells and in addition causes rounding of the cells and increase in steroid synthesis without increase in cyclic AMP. It is also known that if adrenal cells are grown on surfaces treated with poly(HEMA), the cells grow in rounded form and steroid synthesis is increased in proportion to the degree of rounding ( r = 0.92). This response does not involve increase in cellular levels of cylic AMP. It is proposed that in vivo where the cell is always round and cannot show more than strictly limited change in shape, ACTH activates Ca 2+/calmodulin possibly by redistributing cellular Ca 2+. Ca 2+/calmodulin in turn promotes phosphorylation of vimentin and myosin light chain. The first of these phosphorylations shortens intermediate filaments and the second promotes contraction of the actomoyosin ring with internal shortening and approximation of lipid droplets and mitochondria. Details of the earlier events (activation of Ca 2+/calmodulin) and later changes (transfer of cholesterol to the inner membrane) remain to be elucidated. It is clear however that the action of ACTH requires increase in cellular cyclic AMP. These experimental responses bypass this step in the response to ACTH. 相似文献
10.
Light-dependent Ca 2+ efflux via the Ca 2+/H + antiport in the photosynthetic purple sulfur bacterium Chromatium vinosum was inhibited by three phenothiazines: chlorpromazine; trifluoperazine and phenothiazine. The inhibitors had no effect on Ca 2+ uptake by C. vinosum in the dark nor any effect on the light-dependent efflux of either Na + or Tl + catalyzed, respectively, by the C. vinosum Na +/H + or K +/H + antiports. Ruthenium red and LaCl 3, neither of which inhibited light-dependent Ca 2+ efflux in C. vinosum, markedly inhibited Ca 2+ uptake in the dark by C. vinosum cells. Ruthenium red had no effect on the uptake of either Na +or the K + analog T1 + by C. vinosum cells in the dark. These results have been interpreted in terms of two separate Ca 2+ transport systems in C. vinosum: (i) a phenothiazine-sensitive and ruthenium red, La 3+-insensitive Ca 2+/H + antiport responsible for Ca 2+ efflux in the light; and (ii) a ruthenium red and La 3+-sensitive but phenothiazine-insensitive Ca 2+ uptake system. 相似文献
11.
Increase in cytoplasmic cyclic AMP concentration stimulates Ca 2+ influx through the cyclic AMP-gated cation channel in the plasma membrane of cultured carrot cells. However, the Ca 2+ current terminated after a few minutes even in the presence of high concentrations of cyclic AMP indicating that hydrolysis of the nucleotide is not responsible for stop of the Ca 2+ influx. Cyclic AMP evoked discharge of Ca 2+ from inside-out sealed vesicles of carrot plasma membrane, and it was strongly inhibited when the suspension of the vesicles was supplemented with 1 μM of free Ca 2+, while Ca 2+ lower than 0.1 μM did not affect the Ca 2+-release. The Ca 2+ flux across plasma membrane was restored from this Ca 2+-induced inhibition by the addition of calmodulin inhibitors or anti-calmodulin. These results suggest that Ca 2+ influx initiated by the increase in intracellular cAMP in cultured carrot cells is terminated when the cytosolic Ca 2+ concentration reaches the excitatory level in the cells, and calmodulin located in the plasma membrane plays an important role in the response decay of the cyclic nucleotide-gated Ca 2+ channel. 相似文献
12.
Calcium activation of oxygen evolution from French-press preparations of Phormidium luridum is largely reversible upon removal of added Ca 2+. Activation occurs via a first-order binding with a dissociation constant of 2.8 mM. An 8-fold increase in oxygen evolution rate observed upon Ca 2+ addition is accounted for by a 4-fold increase in the number of active photosynthetic units, and a doubling of turnover rate. While both Ca 2+ and Mg 2+ stimulate turnover, unit activation is Ca 2+ specific. Under optimal conditions, 30% of the units functioning in the intact cell can be recovered in the Ca 2+-activated preparation. The Ca2+ requirement of P. luridum preparations is not relieved by proton-carrying uncouplers, or by rate-saturating concentrations of the Hill acceptor, ferricyanide. Taken together with the reported stimulation by Ca2+ of oxygen evolution in the presence of DCMU (Piccioni, R.G. and Mauzerall, D.C. (1976) Biochim. Biophys. Acta 423, 605–609) these observations strongly suggest a site of Ca2+ action within Photosystem II. The pronounced specificity of the Ca2+ requirement appears in preparations of other cyanobacteria (Anabaena flos-aquae and Anacystis nidulans) but not in the eucaryote Chlorella vulgaris. While milder cell-disruption methods bring about some Ca2+ dependence in P. luridum, French-press treatment is required for maximal expression of Ca2+-specific effects. French-press breakage causes a release of endogenous Ca2+ from cells, supporting the view that added Ca2+ restores oxygen evolution by satisfying a physiological requirement for the cation. 相似文献
13.
Measurements of Ca 2+ influx and [Ca 2+] i changes in Fura-2/AM-loaded prothoracic glands (PGs) of the silkworm, Bombyx mori, were used to identify Ca 2+ as the actual second messenger of the prothoracicotropic hormone (PTTH) of this insect. Dose-dependent increases of [Ca 2+] i in PG cells were recorded in the presence of recombinant PTTH (rPTTH) within 5 minutes. The rPTTH-mediated increases of [Ca 2+] i levels were dependent on extracellular Ca 2+. They were not blocked by the dihydropyridine derivative, nitrendipine, an antagonist of high-voltage-activated (HVA) Ca 2+ channels, and by bepridil, an antagonist of low-voltage-activated (LVA) Ca 2+ channels. The trivalent cation La 3+, a non-specific blocker of plasma membrane Ca 2+ channels, eliminated the rPTTH-stimulated increase of [Ca 2+] i levels in PG cells and so did amiloride, an inhibitor of T-type Ca 2+ channels. Incubation of PG cells with thapsigargin resulted in an increase of [Ca 2+] i levels, which was also dependent on extracellular Ca 2+ and was quenched by amiloride, suggesting the existence of store-operated plasma membrane Ca 2+ channels, which can also be inhibited by amiloride. Thapsigargin and rPTTH did not operate independently in stimulating increases of [Ca 2+] i levels and one agent’s mediated increase of [Ca 2+] i was eliminated in the presence of the other. TMB-8, an inhibitor of intracellular Ca 2+ release from inositol 1,4,5 trisphosphate (IP 3)-sensitive Ca 2+ stores, blocked the rPTTH-stimulated increases of [Ca 2+] i levels, suggesting an involvement of IP 3 in the initiation of the rPTTH signaling cascade, whereas ryanodine did not influence the rPTTH-stimulated increases of [Ca 2+] i levels. The combined results indicate the presence of a cross-talk mechanism between the [Ca 2+] i levels, filling state of IP 3-sensitive intracellular Ca 2+ stores and the PTTH-receptor’s-mediated Ca 2+ influx. 相似文献
14.
Most cardiac Na + channels open transiently upon membrane depolarization and then are quickly inactivated. However, some channels remain active, carrying the so-called persistent or late Na + current ( INaL) throughout the action potential (AP) plateau. Experimental data and the results of numerical modeling accumulated over the past decade show the emerging importance of this late current component for the function of both normal and failing myocardium. INaL is produced by special gating modes of the cardiac-specific Na + channel isoform. Heart failure (HF) slows channel gating and increases INaL, but HF-specific Na + channel isoform underlying these changes has not been found. Na + channels represent a multi-protein complex and its activity is determined not only by the pore-forming subunit but also by its auxiliary β subunits, cytoskeleton, calmodulin, regulatory kinases and phosphatases, and trafficking proteins. Disruption of the integrity of this protein complex may lead to alterations of INaL in pathological conditions. Increased INaL and the corresponding Na + flux in failing myocardium contribute to abnormal repolarization and an increased cell Ca 2+ load. Interventions designed to correct INaL rescue normal repolarization and improve Ca 2+ handling and contractility of the failing cardiomyocytes. This review considers (1) quantitative integration of INaL into the established electrophysiological and Ca 2+ regulatory mechanisms in normal and failing cardiomyocytes and (2) a new therapeutic strategy utilizing a selective inhibition of INaL to target both arrhythmias and impaired contractility in HF. 相似文献
15.
In order to examine intracellular modulation of CNS catecholamine release, cerebrocortical synaptosomes were prelabeled with [ 3H]noradrenaline and permeabilized with streptolysin-O in the absence or presence of Ca 2+. Plasma membrane permeabilization allowed efflux of cytosol and left a compartmentalized pool of [ 3H]noradrenaline intact, approximately 10% of which was released by addition of 10 −5 M Ca 2+. Addition of activators or inhibitors of protein kinase C, as well as inhibitors of Ca 2+-calmodulin kinase II or calcineurin, failed to change Ca 2+-induced noradrenaline release. Evoked release from permeabilized synaptosomes deficient in the vesicle-associated phosphoprotein synapsin I was also unchanged. In contrast, addition of a synthetic ‘active domain’ peptide from the myristoylated, alanine-rich C-kinase substrate (MARCKS) protein increased, while addition of calmodulin decreased Ca 2+-induced release from the permeabilized synaptosomes, the latter effect being reversed by a peptide inhibitor of calcineurin. Moreover, addition of the actin-destabilizing agent DNase I, as well as antibodies to MARCKS, appeared to increase spontaneous, Ca 2+-independent release from noradrenergic vesicles. These results indicate that the MARCKS protein may modulate release from permeabilized noradrenergic synaptosomes, possibly by modulating calmodulin levels and/or the actin cytoskeleton. 相似文献
16.
By mediating the Ca 2+ influx that triggers exocytotic fusion, Ca 2+ channels play a central role in a wide range of secretory processes. Ca 2+ channels consist of a complex of protein subunits, including an 1 subunit that constitutes the voltage-dependent Ca 2+-selective membrane pore, and a group of auxiliary subunits, including β, γ, and 2–δ subunits, which modulate channel properties such as inactivation and channel targeting. Subtypes of Ca 2+ channels are constituted by different combinations of 1 subunits (of which 10 have been identified) and auxiliary subunits, particularly β (of which 4 have been identified). Activity-secretion coupling is determined not only by the biophysical properties of the channels involved, but also by the relationship between channels and the exocytotic apparatus, which may differ between fast and slow types of secretion. Colocalization of Ca 2+ channels at sites of fast release may depend on biochemical interactions between channels and exocytotic proteins. The aim of this article is to review recent work on Ca 2+ channel structure and function in exocytotic secretion. We discuss Ca 2+ channel involvement in selected types of secretion, including central neurotransmission, endocrine and neuroendocrine secretion, and transmission at graded potential synapses. Several different Ca 2+ channel subtypes are involved in these types of secretion, and their function is likely to involve a variety of relationships with the exocytotic apparatus. Elucidating the relationship between Ca 2+ channel structure and function is central to our understanding of the fundamental process of exocytotic secretion. 相似文献
17.
Fluoxetine, a selective 5-HT uptake inhibitor, inhibited 15 mM K +-induced [ 3H] 5-HT release from rat spinal cord and cortical synaptosomes at concentrations > 0.5 uM. This effect reflected a property shared by another selective 5-HT uptake inhibitor paroxetine but not by less selective uptake inhibitors such as amitriptyline, desipramine, imipramine or nortriptyline. Inhibition of release by fluoxetine was inversely related to both the concentration of K + used to depolarize the synaptosomes and the concentration of external Ca 2+. Experiments aimed at determining a mechanism of action revealed that fluoxetine did not inhibit voltage-independent release of [ 3H] 5-HT release induced by the Ca 2+-ionophore A 23187 or Ca 2+-independent release induced by fenfluramine. Moreover the 5-HT autoreceptor antagonist methiothepin did not reverse the inhibitory actions of fluoxetine on K +-induced release. Further studies examined the effects of fluoxetine on voltage-dependent Ca 2+ channels and Ca 2+ entry. Whereas fluoxetine and paroxetine inhibited binding of [ 3H] nitrendipine to the dihydropyridine-sensitive L-type Ca 2+ channel, the less selective uptake inhibitors did not alter binding. The dihydropyridine antagonist nimodipine partially blocked fluoxetine-induced inhibition of release. Moreover enhanced K +-stimulated release due to the dihydropyridine agonist Bay K 8644 was reversed by fluoxetine. Fluoxetine also inhibited the K +-induced increase in intracellular free Ca 2+ in fura-2 loaded synaptosomes. These data are consistent with the suggestion that fluoxetine inhibits K +-induced [ 3H] 5-HT release by antagonizing voltage-dependent Ca 2+ entry into nerve terminals. 相似文献
18.
Voltage-dependent Ca 2+ channels are considered as molecular trigger elements for signal transmission at chemical synapses. Due to their central role in this fundamental process, function and pharmacology of presynaptic Ca 2+ channels have recently been the subject of extensive exploration employing various experimental techniques. Several lines of evidence indicate that, at nerve terminals in higher vertebrates, the evoked influx of Ca 2+-ions is mainly mediated by Ca 2+ channels of the P-type. The stringent regulation of presynaptic Ca 2+ channels is supposed to be involved in fine-tuning the efficiency of synaptic transmission. Intrinsic control mechanisms, such as voltage- or Ca 2+-dependent inactivation, or modulation of channel activity, either by G-proteins directly or via phosphorylation by protein kinases, may be of particular functional importance. 相似文献
19.
Excess levels of circulating amino acids (AAs) play a causal role in specific human pathologies, including obesity and type 2 diabetes. Moreover, obesity and diabetes are contributing factors in the development of cancer, with recent studies suggesting that this link is mediated in part by AA activation of mammalian target of rapamycin (mTOR) Complex 1. AAs appear to mediate this response through class III phosphatidylinositol 3-kinase (PI3K), or human vacuolar protein sorting 34 (hVps34), rather than through the canonical class I PI3K pathway used by growth factors and hormones. Here we show that AAs induce a rise in intracellular Ca 2+ ([Ca 2+] i), which triggers mTOR Complex 1 and hVps34 activation. We demonstrate that the rise in [Ca 2+] i increases the direct binding of Ca 2+/calmodulin (CaM) to an evolutionarily conserved motif in hVps34 that is required for lipid kinase activity and increased mTOR Complex 1 signaling. These findings have important implications regarding the basic signaling mechanisms linking metabolic disorders with cancer progression. 相似文献
20.
The interaction of the novel CCK analogs JMV-180, JMV-320, and JMV-332 with CCK-B/gastrin receptors on small cell lung cancer (SCLC) cells was investigated. JMV-180, JMV-320, and JMV-332 potently inhibited specific binding of 125I-CCK-8 to CCK-B/gastrin receptors expressed on the SCLC cell line NCI-H345 (H345) with IC 50 values of 4.9, 1.8, and 7.0 n M, respectively. JMV-320 and JMV-332 stimulated intracellular calcium ([Ca 2+] i) release in a dose-dependent manner in cells preloaded with indo-1. JMV-180 did not stimulate [Ca 2+] i but inhibited the [Ca 2+] i release elicited by 10 n M CCK-8 in a dose-dependent manner. These data indicate that JMV-320 and JMV-332 function as CCK-B/gastrin receptor agonists while JMV-180 functions as a CCK-B/gastrin receptor antagonist in H345 cells. 相似文献
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