共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Leoni S. Spagnuolo F. Terenzi M. Marino C. Bolaffi F. M. Pulcinelli M. T. Mangiantini 《Bioscience reports》1993,13(1):53-60
The changes in intracellular calcium concentration and IP3 production after the addition of epinephrine were analysed in adult, fetal (20th–22nd day of intrauterine life), and regenerating rat hepatocytes (4 h–24 h after partial hepatectomy) to determine whether the signal transduction is the same in quiescent proliferating and differentiating cells.The epinephrine treatment causes a significative cytosolic calcium transient in hepatocytes isolated in the last day of fetal life (22-day old) and in the early stage of regeneration (4 h). This effect is not significant in the previous stage of fetal life (20-day old) and at the onset of M phase of cell cycle after partial hepatectomy (24 h).[3H]myo inositol incorporation into IP3 and IP4 is higher in 20 day fetal and regenerating hepatocytes with respect to the control. In these cells the epinephrine does not affect basal level of IP3 and IP4, while it causes a substantial increase of these inositol phosphates in adult hepatocytes.[3H]myo inositol incorporation into PIP2 is very low at the 20th day of fetal life. Epinephrine has no effect on this parameter in fetal and regenerating hepatocytes.Our results show that the epinephrine signal is mediated differently in proliferating and in quiescent hepatocytes. 相似文献
2.
The effect of epinephrine on the amino acid transport mediated by system A was investigated by determining the uptake of 2-amino [1-14C]isobutyric acid (AIB) in rat hepatocytes, freshly isolated at different stages of pre- and postnatal development. The data obtained show that the hormone increased AIB uptake, enhancing the Vmax, while Km was unchanged. This effect was evident in cells from adult, 18- to 20-day-old fetus, and neonate rat. Actinomycin D or cycloheximide abolished the hormone dependent increase. Experiments carried out with alpha- and beta-antagonists showed that the effect of epinephrine was beta-mediated in fetal life and alpha-mediated in adult life. Membrane binding experiments showed a higher value for epinephrine and beta-agonist dihydroalprenolol in the fetus versus the adult. The calcium depletion obtained after cell incubation with EGTA or calcium ionophore A23187 reduced the hormonal stimulation in the adult, and was ineffective in the prenatal period. An involvement of cAMP was present in the epinephrine modulation of AIB transport, both in adult and in fetal life. 相似文献
3.
Peercy BE 《Journal of computational neuroscience》2008,25(2):334-348
The ability to image calcium movement within individual neurons inspires questions of functionality including whether calcium
entry into the nucleus is related to genetic regulation for phenomena such as long term potentiation. Calcium waves have been
initiated in hippocampal pyramidal cells with glutmatergic signals both in the presence and absence of back propagating action
potentials (BPAPs). The dendritic sites of initiation of these calcium waves within about 100 μm of the soma are thought to
be localized near oblique junctions. Stimulation of synapses on oblique dendrites leads to production of inositol 1,4,5-trisphosphate
(IP3) which diffuses to the apical dendrite igniting awaiting IP3 receptors (IP3Rs) and initiating and propagating catalytic calcium release from the endoplasmic reticulum. We construct a reduced mathematical
system which accounts for calcium wave initiation and propagation due to elevated IP3. Inhomogeneity in IP3 distribution is responsible for calcium wave initiation versus subthreshold or spatially uniform suprathreshold activation.
However, the likelihood that a calcium wave is initiated does not necessarily increase with more calcium entering from BPAPs.
For low transient synaptic stimuli, timing between IP3 generation and BPAPs is critical for calcium wave initiation. We also show that inhomogeneity in IP3R density can account for calcium wave directionality. Simulating somatic muscarinic receptor production of IP3, we can account for the critical difference between calcium wave entry into the soma and failure to do so. 相似文献
4.
S. Leoni S. Spagnuolo M. Massimi F. Terenzi L. Conti Devirgiliis 《Bioscience reports》1992,12(2):135-141
Amino acid uptake mediated by system A was studied in cultured fetal and adult hepatocytes, subjected to growth stimulation
by EGF and insulin, or to growth inhibition by high cell density.
The mitogenic stimulation induced a strong transport increase only in fetal cells, while the cell density-dependent growth
inhibition, probably mediated by molecules present on adult hepatocyte membranes, provoked the decrease of amino acid uptake
only in the adult cells.
The results indicate that the different modulation of amino acid transport by cell growth is dependent on the age and the
differentiation stage of hepatocytes. 相似文献
5.
The influence of stochastic inositol-1,4,5-trisphosphate receptor (IP3R) dynamics and their clustering have been extensively investigated to explore the mechanism through which the stochastic molecular event finally shape the intracellular calcium signaling. Most of the previous works employed simplified models which take the concentration of IP3 instead of that of the agonist as the stimulation intensity. However, the IP3 level is not linearly dependent on the agonist concentration in stimulus induced signaling systems because there are feedback links in the transduction network. In this work, we include both the IP3R dynamics and the typical agonist induced signaling transduction cascade in the model to investigate the essential influence of stochastic IP3R dynamics on the coding of the stimulus induced calcium signal. Simulation results reveal two distinct oscillation areas under different stimulation levels. The signal is optimally modulate by the IP3R cluster number in the weak stimulated area while affected by the stimulus intensity in the strong stimulated area. Different dependences of coefficient of variance (CV) on the number of clusters are obtained in these two areas, which explains the disagreement in the previous reported results. Besides, the transition between these areas explains the significant CV reduction observed in experiments. 相似文献
6.
Glucagon and cAMP analogs stimulate amino acid transport in freshly isolated hepatocytes by inducing the synthesis of new transport proteins. The role of the cell nucleus in the glucagon regulation of amino acid transport has been studied in rat hepatocytes enucleated by centrifugation through a discontinuous Ficoll gradient in the presence of cytochalasin B. Enucleated hepatocytes take up alpha-aminoisobutyric acid (AIB) through a Na+-dependent transport component with kinetic properties similar to those found in intact hepatocytes. Cytoplasts prepared from glucagon-stimulated cells retain the increase AIB transport induced by the hormone in the intact cells. The direct addition of glucagon to cytoplasts has no effect on AIB transport, in spite of the fact that the cytoplasts exhibit a higher capacity to bind glucagon than their nucleated counterparts. These data indicate that the nucleus is required for the glucagon stimulation of amino acid transport in isolated hepatocytes. 相似文献
7.
Ondrias K Lencesova L Sirova M Labudova M Pastorekova S Kopacek J Krizanova O 《Journal of cellular physiology》2011,226(12):3147-3155
Inositol 1,4,5‐trisphosphate (IP3) receptors are emerging as key sites for regulation by pro‐ and anti‐apoptotic factors. Induction of apoptosis for 3 h increased mRNA and protein levels of type 1 IP3 receptors in non‐differentiated (ND), but not in differentiated (D) PC12 cells. Inhibitors of the IP3R's calcium release—2‐aminoethoxydiphenyl borate (2‐APB) and xestospongin—completely prevented Bax and caspase‐3 mRNA increase after treatment with the apoptosis inducer set (AIK), and this reinforces the importance of IP3R1 in the apoptosis of ND PC12 cells. Apoptosis induction not only increases the IP3R1 protein, but it also causes formation of IP3R1 clusters in the nucleus which most likely result from fusion of the nucleoplasmic reticulum and/or IP3R1 translocation to the nucleus. This is quite similar to the observations noted after overexpression of IP3R1 in PC12 cells. The amount of IP3 induced calcium release was higher in control than in AIK‐treated cells. From our results we propose that after the apoptosis induction the amount of intranuclear calcium decreased dramatically due to the increase of calcium permeability of the nuclear calcium store vesicles. Therefore, increase of the calcium permeability may result from IP3 receptors translocation to nuclei that can boost the calcium transport through IP3 receptors. J. Cell. Physiol. 226: 3147–3155, 2011. © 2011 Wiley Periodicals, Inc. 相似文献
8.
Soo Kyung Lim Luc Cynober Jean-Pascal DE Bandt Christian Aussel 《Cell biology international》1999,23(1):7-12
The effects of glucagon on amino acid transport in rat hepatocytes are not fully understood. We examined the effect of this hormone on alanine, serine and cysteine preferring system (system ASC)-mediated amino acid transport in rat hepatocyte monolayers using 2-aminoisobutyric acid (AIB) and L -cysteine. Glucagon induced a time and protein synthesis-dependent stimulation of Na+-dependent alanine preferring system (system A)-independent AIB transport. The glucagon-induced increase in transport activity was not modified by substrate starvation and not related to changes in the intracellular pool of amino acids. Glucagon did not modify system ASC activity measured by L -cysteine. Therefore the transport activity of AIB independent of system A stimulated by glucagon cannot be attributed to system ASC. This suggests a Na+-dependent transport system in rat hepatocytes not identified until now. 相似文献
9.
EGF Stimulates Growth by Enhancing Capacitative Calcium Entry in Corneal Epithelial Cells 总被引:2,自引:0,他引:2
Yang H Sun X Wang Z Ning G Zhang F Kong J Lu L Reinach PS 《The Journal of membrane biology》2003,194(1):47-58
In rabbit corneal epithelial cells (RCEC), we determined whether capacitative calcium entry (CCE) mediates the mitogenic response to epidermal growth factor, EGF. [Ca2+]i was measured with single-cell fluorescence imaging of fura2-loaded RCEC. EGF (5 ng/ml) maximally increased [Ca2+]i 4.4-fold. Following intracellular store (ICS) calcium depletion in calcium-free medium with 10 µM cyclopiazonic acid (CPA) (endoplasmic reticulum calcium ATPase inhibitor), calcium addback elicited plasma membrane Ca2+ influx as a result of activation of plasma membrane store operated channel (SOC) activity. Based on Mn2+ quench measurements of fura2 fluorescence, 5 ng/ml EGF enhanced such influx 2.3-fold, whereas with Rp-cAMPS (protein kinase A inhibitor) plus EGF it increased by 5.3-fold. In contrast, SOC activation was blocked with 100 µM 2-aminoethyldiphenylborate (2-APB, store-operated channel inhibitor). During exposure to either 50 µM UO126 (MEK-1/2 inhibitor) or 10 µM forskolin (adenylate cyclase activator), 5 ng/ml EGF failed to affect [Ca2+]i. RT-PCR detected gene expression of: 1) transient receptor potential (TRP) protein isoforms 1, 3, 4, 6 and 7; 2) IP3R isoforms 1–3. Immunocytochemistry, in conjunction with confocal and immunogold electron microscopy, detected plasma membrane localization of TRP4 expression. Inhibition of CCE with 2-APB and/or CPA, eliminated the 2.5-fold increase in intracellular [3H]-thymidine incorporation induced by EGF. Taken together, CCE in RCEC mediates the mitogenic response to EGF. EGF induces CCE through its stimulation of Erk1/2 activity, whereas PKA stimulation suppresses these effects of EGF. TRP4 may be a component of plasma membrane SOC activity, which is stimulated by ICS calcium depletion. 相似文献
10.
Of all available liver cells in culture, only primary cultured hepatocytes are known to respond to glucagon in vitro. In the present study we investigated whether glucagon could stimulate amino acid transport and tyrosine aminotransferase (TAT;EC 2.6.1.5) activity (two well-characterized glucagon effects in the liver) in Fao cells, a highly differentiated rat hepatoma cell line. We found that glucagon had no effect on transport of alpha-aminoisobutyric acid (AIB; a non-metabolizable alanine analogue) nor on TAT activity, even though both activities could be fully induced by insulin [2-fold and 3-fold effects for AIB transport and TAT activity, respectively, after 6h; EC50 (median effective concentration) = 0.3 nM], or by dexamethasone (5-8-fold effects after 20 h; EC50 = 2 nM). Analysis of [125I]iodoglucagon binding revealed that Fao cells bind less than 1% as much glucagon as do hepatocytes, whereas insulin binding in Fao cells was 50% higher than in hepatocytes. The addition of dibutyryl cyclic AMP, which fully mimics the glucagon stimulation of both AIB transport and TAT activity in hepatocytes, induced TAT activity in Fao cells (a 2-fold effect at 0.1 mM-dibutyryl cyclic AMP) but had no effect on AIB transport. Cholera toxin stimulated TAT activity to the same extent as did dibutyryl cyclic AMP. These results indicate that the lack of glucagon responsiveness in cultured hepatoma cells results from both a receptor defect and, for amino acid transport, an additional post-receptor defect. Moreover, the results show that amino acid transport and TAT activity, which appeared to be co-induced by insulin or by dexamethasone in these cells, respond differently to cyclic AMP. This suggests that different mechanisms are involved in the induction of these activities by glucagon in liver. 相似文献
11.
Michael W Harr Karen S McColl Fei Zhong Jason K Molitoris Clark W Distelhorst 《Autophagy》2010,6(7):912-921
T cell receptor activation induces inositol 1,4,5 trisphosphate (IP3)-mediated calcium signaling that is essential for cell metabolism and survival. Moreover, inhibitors of IP3 or pharmacological agents that disrupt calcium homeostasis readily induce autophagy. Using a glucocorticoid-sensitive CD4/CD8 positive T cell line, we found that dexamethasone prevented both IP3-mediated and spontaneous calcium signals within a timeframe that correlated with the induction of autophagy. We determined that this loss in IP3-mediated calcium signaling was dependent upon the downregulation of the Src kinase Fyn at the mRNA and protein level. Because it has previously been shown that Fyn positively regulates IP3-mediated calcium release by phosphorylating Type I IP3 receptors (IP3R1), we investigated the effect of glucocorticoids on IP3R1 phosphorylation at Tyr353. Accordingly, glucocorticoid-mediated downregulation of Fyn prevented IP3R1 phosphorylation at Tyr353. Moreover, selective knockdown of Fyn or treatment with a Src inhibitor also attenuated IP3-mediated calcium release and induced autophagy. Collectively, these data indicate that glucocorticoids promote autophagy by inhibiting IP3-dependent calcium signals. These findings carry important therapeutic implications given the widespread use of dexamethasone as both a chemotherapeutic and immunosuppressive agent.Key words: autophagy, calcium, Fyn, IP3 receptor, dexamethasone 相似文献
12.
In rat brain slices the synthesis of [3H]phosphoinositides and the production of [3H]inositol monophosphate (IP1) induced by norepinephrine (NE) were inhibited by glutamate. Calcium concentrations were varied to test if these inhibitory effects of glutamate were mediated by a calcium-dependent process. Although reducing calcium or addition of the calcium antagonist verpamil reduced the inhibitory effects of glutamate, these results were equivocal because reduced calcium directly decreased agonist-induced [3H]phosphoinositide synthesis. The inhibitory effects of glutamate were mimicked by quisqualate in a dose-dependent manner, but none of a variety of excitatory amino acid receptor antagonists modified the inhibition caused by quisqualate. It is suggested that glutamate activates a quisqualate-sensitive receptor (for which an antagonist is not available) and causes inhibition of phosphoinositide hydrolysis mediated in part by a direct or indirect inhibitory effect of calcium on phosphoinositide synthesis. Modulatory effects of arachidonic acid were examined because glutamate and calcium can activate phospholipase A2. Arachidonic acid caused a rapid and dose-dependent inhibition of [3H]phosphoinositide synthesis and of NE-stimulated [3H]IP1 production. A similar inhibition of the response to carbachol also occurred. The inhibition caused by arachidonic acid was unchanged by addition of inhibitors of cyclooxygenase or lipoxygenase. Activation of phospholipase A2 with melittin caused inhibitory effects similar to those of arachidonic acid. Inhibitors of phospholipase A2 were found to impair phosphoinositide metabolism, likely due to their lack of specificity for phospholipase A2. Further studies were carried out in slices that were prelabelled with [3H]inositol in an attempt to separate modulatory effects on [3H]phosphoinositide synthesis and agonist-stimulated [3H]IP1 production. Several excitatory amino acid agonists inhibited NE-stimulated [3H]IP1 production. This inhibitory inter-action could be due to impaired synthesis of [3H]phosphoinositides because, even though the slices were prelabeled, addition of unlabelled inositol reduced NE-stimulated [3H]IP1 production, indicating that continuous regeneration of [3H]phosphoinositides is required. In contrast to the inhibitory effects of the excitatory amino acids, gamma-aminobutyric acid (GABA) enhanced the response to NE in cortical and hippocampal slices. GABA also enhanced the response to carbachol in hippocampal and striatal slices and to ibotenic acid in hippocampal slices. Baclofen potentiated the response to NE similarly to the effect of GABA and baclofen partially blocked the inhibitory effect of arachidonic acid but did not alter that of quisqualate.Abbreviations AMPA
-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
- acid AP4
dl-2-amino-4-phosphonobutyric acid
- BPB
bromphenacyl bromide
- BSA
bovine serum albumin
- CNQX
6-cyano-7-nitroquinoxaline-2,3-dione
- DFMO
-difluoromethylornithine
- DIDS
diisothiocyanotostilbene-2,2-disulfonic acid
- EGTA
ethyleneglycol-bis-N
- N, N
N-tetraacetic acid
- GABA
-aminobutyric acid
- GDEE
glutamate diethyl ether
- -GG
-glutamylglycine
- IP1
inositol monophosphate
- IP2
inositol bisphosphate
- IP3
inositol trisphosphate
- NDGA
nordihydroguaiaretic acid
- NE
norepinephrine
- NMDA
N-methyl-d-aspartate 相似文献
13.
《Autophagy》2013,9(7):912-921
T cell receptor activation induces inositol 1,4,5 trisphosphate (IP3)-mediated calcium signaling that is essential for cell metabolism and survival. Moreover, inhibitors of IP3 or pharmacological agents that disrupt calcium homeostasis readily induce autophagy. Using a glucocorticoid-sensitive CD4/CD8 positive T cell line, we found that dexamethasone prevented both IP3-mediated and spontaneous calcium signals within a timeframe that correlated with the induction of autophagy. We determined that this loss in IP3-mediated calcium signaling was dependent upon the downregulation of the Src kinase Fyn at the mRNA and protein level. Because it has previously been shown that Fyn positively regulates IP3-mediated calcium release by phosphorylating Type I IP3 receptors (IP3R1), we investigated the effect of glucocorticoids on IP3R1 phosphorylation at Tyr353. Accordingly, glucocorticoid-mediated downregulation of Fyn prevented IP3R1 phosphorylation at Tyr353. Moreover, selective knockdown of Fyn or treatment with a Src inhibitor also attenuated IP3-mediated calcium release and induced autophagy. Collectively, these data indicate that glucocorticoids promote autophagy by inhibiting IP3-dependent calcium signals. These findings carry important therapeutic implications given the widespread use of dexamethasone as both a chemotherapeutic and immunosuppressive agent. 相似文献
14.
T Mine I Kojima E Ogata T Nakamura 《Biochemical and biophysical research communications》1991,181(3):1173-1180
We compared the effects of HGF and EGF on cytoplasmic free calcium concentration, [Ca2+]c, and inositol trisphosphate production in rat hepatocytes. HGF induced a prompt and transient elevation of [Ca2+]c. EGF also induced an immediate increase in [Ca2+]c, the magnitude of which was greater than that by HGF. In contrast, in the presence of 1 microM extracellular calcium EGF increased [Ca2+]c to a lesser extent than HGF. When cells were pretreated with EGF, the effect of HGF on [Ca2+]c was greatly enhanced. However, such enhancement was not observed in medium containing 1 microM extracellular calcium. In hepatocytes prelabeled with [3H]-inositol, both HGF and EGF increased [3H]inositol trisphosphate. HGF and EGF acted synergistically to stimulate production of inositol trisphosphate. These results indicate that both HGF and EGF increase [Ca2+]c by a mechanism involving phosphoinositide turnover and that the actions of HGF and EGF on hepatocyte calcium metabolism are not totally identical. 相似文献
15.
Etherton B 《Plant physiology》1978,62(6):933-937
Microelectrode and tracer techniques were used to test for possible amino acid-H+ co-transport in coleoptiles of Avena sativa L. cv. “Garry.” The amino acid analogue α-aminoisobutyric acid (AIB) caused transient depolarization of the membrane potential. The absolute magnitude of the maximum depolarization was affected by the same factors that affected AIB transport. Both increased with higher concentrations of AIB, increased with higher acidities in the medium, and were enhanced by indoleacetic acid (which hyperpolarized the membrane potential). AIB transport was reduced as K+ concentrations in the medium were increased and by the metabolic inhibitor NaN3, both of which reduce membrane potentials. Our data fit an amino acid-H+ co-transport model in which transport is controlled by both the membrane potential and proton concentration components of the chemical potential difference of protons across the coleoptile cell membrane. 相似文献
16.
Transmembrane potential (Em) and alpha-aminoisobutyric acid (AIB) transport were measured in primary monolayer cultures of rat hepatocytes obtained from unoperated control rats and from rats 12 hr following partial hepatectomy. Measurements were performed 20–24 hr after plating the cells. The capacity of both kinds of cells to concentrate AIB depended upon extracellular sodium; however, the steady-state accumulation in regenerating cells was twice that of control cells. Transmembrane potentials, recorded with glass microelectrodes, were –13 ± 0.6 mV and –27 ± 1.6 mV in control and regenerating cells, respectively. Ouabain (1 mM) depolarlized regenerating cells to –18 ± 1.0 mV, but it had no effect on control cells. The initial rates of 1 mM AIB transport into control and regenerating cells were 1.2 ± 0.1 and 3.1 ± 0.1 nanomoles/mg protein × 4 min, respectively. Ouabain (1 mM) reduced the initial rate of AIB transport into regenerating cells to 2.7 ± 0.1 nanomoles/mg protein × 4 min, but it had no effect on AIB transport into control cells. Glucagon (10?7 M) added to control cells 12 hr before measurements hyperpolarized Em to –31 ± 1.3 mV and increased AIB transport rate to 3.1 nanomoles/mg protein × 4 min. The results suggest a relationship between increases in Em and increases in AIB transport in rat hepatocytes. An electrogenic Na-K pump may be involved in both of these events. 相似文献
17.
18.
An acetylcholine (ACh) agonist, carbachol (Cch), causes hepatocytes to proliferate in the presence of hepatic nonparenchymal cells (HNPCs). To identify the HNPCs and ACh receptor subtypes involved in carbachol-induced hepatocyte proliferation (CIHP), we examined two types of vascular cells as candidates for HNPCs mediating CIHP in cocultures of hepatocytes using the Transwell filter insert. In the coculture with vascular smooth muscle cells (VSMCs) or endothelial cells (VECs), but not in the monoculture, 72 h treatment with Cch significantly increased the numbers of hepatocytes. The results suggest that both VSMCs and VECs are involved in CIHP through soluble factors secreted from these cells. Interestingly, coculture with VECs, but not with VSMCs, markedly increased the number of hepatocytes, even in the absence of Cch. Cell proliferation assays using an analogue of thymidine, bromodeoxyuridine (BrdU), demonstrated that the hepatocytes in both cocultures transiently replicated their chromosomes 12 h after Cch administration. Blocking the muscarinic type 1 ACh receptor (M1), M3/5, intracellular inositol triphosphate (IP3) receptor, or protein kinase C (PKC) pathways inhibited VSMC-mediated CIHP, whereas blocking the M3/5, IP3 receptor, or PKC pathways inhibited VEC-mediated CIHP. Co-culturing hepatocytes with both types of vascular cells markedly increased their albumin content, but addition of Cch had no effect. In conclusion, VSMCs among vascular cells mediate CIHP through M1, M3/5, and IP3/PKC signal transduction pathways, whereas VECs do so through M3/5, and IP3/PKC pathways. 相似文献
19.
Joon-Chul Kim Min-Jeong Son Krishna P. Subedi Do Han Kim Sun-Hee Woo 《Molecules and cells》2010,29(4):387-395
HL-1 cells are the adult cardiac cell lines available that continuously divide while maintaining an atrial phenotype. Here
we examined the expression and localization of inositol 1,4,5-trisphosphate receptor (IP3R) subtypes, and investigated how pattern of IP3-induced subcellular local Ca2+ signaling is encoded by multiple IP3R subtypes in HL-1 cells. The type 1 IP3R (IP3R1) was expressed in the perinucleus with a diffuse pattern and the type 2 IP3R (IP3R2) was expressed in the cytosol with a punctate distribution. Extracellular ATP (1 mM) elicited transient intracellular Ca2+ releases accompanied by a Ca2+ oscillation, which was eliminated by the blocker of IP3Rs, 2-APB, and attenuated by ryanodine. Direct introduction of IP3 into the permeabilized cells induced Ca2+ transients with Ca2+ oscillations at ⩾ 20 μM of IP3, which was removed by the inhibition of IP3Rs using 2-APB and heparin. IP3-induced local Ca2+ transients contained two distinct time courses: a rapid oscillation and a monophasic Ca2+ transient. The magnitude of Ca2+ oscillation was significantly larger in the cytosol than in the nucleus, while the monophasic Ca2+ transient was more pronounced in the nucleus. These results provide evidence for the molecular and functional expression
of IP3R1 and IP3R2 in HL-1 cells, and suggest that such distinct local Ca2+ signaling may be correlated with the punctate distribution of IP3R2s in the cytosol and the diffuse localization of IP3R1 in the peri-nucleus. 相似文献
20.
Wenjing Xing Guangwei Li Yuhui Xi Jin Guo Hongzhu Li Hongxia Li Weihua Zhang Li Zhang Lingyun Wu Rui Wang Changqing Xu 《Molecular and cellular biochemistry》2010,343(1-2):13-19
The calcium-sensing receptors (CaSRs) exist in a variety of tissues and cells. In 2001, Canaff et al. first identified its expression in liver tissue and primary cultured hepatocytes, and demonstrated that GdCl3 (a specific agonist of CaSR) can cause an increase in intracellular calcium and bile flow. However, authors did not elucidate its mechanisms. Therefore, this study sought to detect CaSR expression in BRL cell line, which is derived from buffalo rat liver, and to reveal the cellular signal transduction pathway by which the CaSR activation results in increased intracellular calcium by BRL cells. In this study, the expression and distribution of CaSR were detected by RT-PCR, Western blotting, and immunofluorescence, and the intracellular calcium concentration [Ca2+]i was measured using LCSM. The results showed that CaSR mRNA and protein were expressed in BRL cells and mainly distributed in cell membrane and cytoplasm. Increased extracellular calcium or GdCl3 could increase intracellular calcium concentration and CaSR expression. Moreover, this increase of [Ca2+]i could be inhibited or even abolished by U73122 (a specific inhibitor of PLC), 2-APB (an inhibitor of IP3 receptor), and thapsigargin (an inhibitor of endoplasmic reticulum calcium pump). In conclusion, CaSR is functionally expressed in BRL cells, and activation of CaSR involves in increased intracellular calcium through Gq–PLC–IP3 pathway. 相似文献