scholarly journals K201 (JTV519) suppresses spontaneous Ca2+ release and [3H]ryanodine binding to RyR2 irrespective of FKBP12.6 association

2007 ◽  
Vol 404 (3) ◽  
pp. 431-438 ◽  
Author(s):  
Donald J. Hunt ◽  
Peter P. Jones ◽  
Ruiwu Wang ◽  
Wenqian Chen ◽  
Jeff Bolstad ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Dependent Manner ◽  
Wild Type ◽  
Concentration Dependent Manner ◽  
Hek 293 ◽  
Human Embryonic Kidney Cells ◽  
Hek 293 Cells ◽  
Fk506 Binding Protein ◽  
293 Cells

K201 (JTV519), a benzothiazepine derivative, has been shown to possess anti-arrhythmic and cardioprotective properties, but the mechanism of its action is both complex and controversial. It is believed to stabilize the closed state of the RyR2 (cardiac ryanodine receptor) by increasing its affinity for the FKBP12.6 (12.6 kDa FK506 binding protein) [Wehrens, Lehnart, Reiken, Deng, Vest, Cervantes, Coromilas, Landry and Marks (2004) Science 304, 292–296]. In the present study, we investigated the effect of K201 on spontaneous Ca2+ release induced by Ca2+ overload in rat ventricular myocytes and in HEK-293 cells (human embryonic kidney cells) expressing RyR2 and the role of FKBP12.6 in the action of K201. We found that K201 abolished spontaneous Ca2+ release in cardiac myocytes in a concentration-dependent manner. Treating ventricular myocytes with FK506 to dissociate FKBP12.6 from RyR2 did not affect the suppression of spontaneous Ca2+ release by K201. Similarly, K201 was able to suppress spontaneous Ca2+ release in FK506-treated HEK-293 cells co-expressing RyR2 and FKBP12.6. Furthermore, K201 suppressed spontaneous Ca2+ release in HEK-293 cells expressing RyR2 alone and in cells co-expressing RyR2 and FKBP12.6 with the same potency. In addition, K201 inhibited [3H]ryanodine binding to RyR2-wt (wild-type) and an RyR2 mutant linked to ventricular tachycardia and sudden death, N4104K, in the absence of FKBP12.6. These observations demonstrate that FKBP12.6 is not involved in the inhibitory action of K201 on spontaneous Ca2+ release. Our results also suggest that suppression of spontaneous Ca2+ release and the activity of RyR2 contributes, at least in part, to the anti-arrhythmic properties of K201.

Halothane Inhibition of Recombinant Cardiac L-type Ca2+ Channels Expressed in HEK-293 Cells

2005 ◽  
Vol 103 (6) ◽  
pp. 1156-1166 ◽  
Author(s):  
Kevin J. Gingrich ◽  
Son Tran ◽  
Igor M. Nikonorov ◽  
Thomas J. Blanck
Keyword(s):  
Charge Transfer ◽  
Calcium Channels ◽  
Dependent Manner ◽  
Current Time ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Dependent Inactivation ◽  
Voltage Dependent

Background Volatile anesthetics depress cardiac contractility, which involves inhibition of cardiac L-type calcium channels. To explore the role of voltage-dependent inactivation, the authors analyzed halothane effects on recombinant cardiac L-type calcium channels (alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1), which differ by the alpha2/delta1 subunit and consequently voltage-dependent inactivation. Methods HEK-293 cells were transiently cotransfected with complementary DNAs encoding alpha1C tagged with green fluorescent protein and beta2a, with and without alpha2/delta1. Halothane effects on macroscopic barium currents were recorded using patch clamp methodology from cells expressing alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1 as identified by fluorescence microscopy. Results Halothane inhibited peak current (I(peak)) and enhanced apparent inactivation (reported by end pulse current amplitude of 300-ms depolarizations [I300]) in a concentration-dependent manner in both channel types. alpha2/delta1 coexpression shifted relations leftward as reported by the 50% inhibitory concentration of I(peak) and I300/I(peak)for alpha1Cbeta2a (1.8 and 14.5 mm, respectively) and alpha1Cbeta2aalpha2/delta1 (0.74 and 1.36 mm, respectively). Halothane reduced transmembrane charge transfer primarily through I(peak) depression and not by enhancement of macroscopic inactivation for both channels. Conclusions The results indicate that phenotypic features arising from alpha2/delta1 coexpression play a key role in halothane inhibition of cardiac L-type calcium channels. These features included marked effects on I(peak) inhibition, which is the principal determinant of charge transfer reductions. I(peak) depression arises primarily from transitions to nonactivatable states at resting membrane potentials. The findings point to the importance of halothane interactions with states present at resting membrane potential and discount the role of inactivation apparent in current time courses in determining transmembrane charge transfer.

Extracellular signal-regulated kinase activation by parathyroid hormone in distal tubule cells

2007 ◽  
Vol 292 (3) ◽  
pp. F1028-F1034 ◽  
Author(s):  
W. Bruce Sneddon ◽  
Yanmei Yang ◽  
Jianming Ba ◽  
Lisa M. Harinstein ◽  
Peter A. Friedman
Keyword(s):  
Conditioned Media ◽  
Kidney Cells ◽  
Wild Type ◽  
Egfr Transactivation ◽  
Hek 293 ◽  
Erk Activation ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Extracellular Signal

The PTH receptor (PTH1R) activates multiple signaling pathways, including extracellular signal-regulated kinases 1 and 2 (ERK1/2). The role of epidermal growth factor receptor (EGFR) transactivation in ERK1/2 activation by PTH in distal kidney cells, a primary site of PTH action, was characterized. ERK1/2 phosphorylation was stimulated by PTH and blocked by the EGFR inhibitor, AG1478. Upon PTH stimulation, metalloprotease cleavage of membrane-bound heparin-binding fragment (HB-EGF) induced EGFR transactivation of ERK. Conditioned media from PTH-treated distal kidney cells activated ERK in HEK-293 cells. AG1478 added to HEK-293 cells ablated transactivation by conditioned media. HB-EGF directly activated ERK1/2 in HEK-293 cells. Pretreatment of distal kidney cells with the metalloprotease inhibitor GM-6001 abolished transactivation of ERK1/2 by PTH. The role of the PTH1R COOH terminus in PTX-sensitive ERK1/2 activation was characterized in HEK-293 cells transfected with wild-type PTH1R, with a PTH1R mutated at its COOH terminus, or with PTH1R truncated at position 480. PTH stimulated ERK by wild-type, mutated and truncated PTH1Rs 21-, 27- and 57-fold, respectively. Thus, the PTH1R COOH terminus exerts an inhibitory effect on ERK activation. EBP50, a scaffolding protein that binds to the PDZ recognition domain of the PTH1R, impaired PTH but not isoproterenol or calcitonin-induced ERK activation. Pertussis toxin inhibited PTH-stimulated ERK1/2 by mutated and truncated PTH1Rs and abolished ERK1/2 activation by wild-type PTH1R. We conclude that ERK phosphorylation in distal kidney cells by PTH requires PTH1R activation of Gi, which leads to stimulation of metalloprotease-mediated cleavage of HB-EGF and transactivation of the EGFR and is regulated by EBP50.

Abstract 16460: Enhanced Trpc Channel-Mediated Ca2+ Influx in the Cells With Phospholipase C-δ1 Overexpression

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Kazuo Murakami ◽  
Tomohiro Osanai ◽  
Makoto Tanaka ◽  
Kimitaka Nishizaki ◽  
Ikuyo Narita ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Transient Receptor Potential ◽  
Coronary Spasm ◽  
Dependent Manner ◽  
Hek 293 ◽  
Trpc Channel ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Dose Dependent

Background: We recently showed that ergometrine induces coronary spasm in the mice with enhanced phospholipase C (PLC)-δ1 activity, which was detected in patients with coronary spasm (Circulation 2012), and PLC-mediated Ca2+ entry is involved in the genesis of coronary spams. We examined the role of enhanced PLC-δ1 in extracellular Ca2+ entry and its underlying mechanisms in human embryonic kidney (HEK)-293 cells and human coronary arteries smooth muscle cells (CASMC). Methods and Results: The cells were stimulated with acetylcholine (ACh) in a extracellular Ca2+-free condition, and the increase in intracellular free Ca2+ concentration ([Ca2+]i) after addition of extracellular Ca2+ was defined as Ca2+ influx. [Ca2+]i was measured by fura-2. In HEK-293 cells, ACh-induced Ca2+ influx (nM ) was 21±2 in the control and 52±6 in the cells with PLC-δ1 overexpression (p<0.05). ACh-induced Ca2+ influx in the cells with PLC-δ1 overexpression was suppressed by nifedipine in a dose-dependent manner but was partially by 36±13% at 10-5M (p<0.05), thereby even after treatment with nifedipine at 10-5M, ACh-induced Ca2+ influx was increased by 2.9±0.1 times by enhanced PLC-δ1 compared with the control (p<0.05). To clarify the role of diacylglycerol (DAG) in Ca2+ influx, the effect of blockers for DAG-activated transient receptor potential (TRPC) channel was examined. ACh-induced Ca2+ influx in the cells with PLC-δ1 overexpression was suppressed by 2-APB, an inhibitor of non-selective cation channel TRPC, in a dose-dependent manner, and was almost completely blocked by 89±12% at 10-4M (p<0.05). While TRPC3 siRNA did not affect ACh-induced Ca2+ influx (59±27 vs 75±23 nM, p=ns), TRPC6 siRNA suppressed Ca2+ influx to 37±28 nM (p<0.05). In human CASMC, ACh-induced Ca2+ influx was 41±11 in the control and 64±15 in the cells with PLC-δ1 overexpression (p<0.05). Like HEK-293 cells, pretreatment with nifedipine partially suppressed Ca2+ influx, whereas either 2-APB or TRPC6 siRNA almost completely blocked it. Conclusion: ACh-induced Ca2+ influx, mediated by both voltage-gated Ca2+ channels and non-selective cation channels TRPC6, is enhanced by PLC-δ1 overexpression. Inhibition of TRPC may be effective in enhanced PLC-δ1-mediated coronary spasm.

Intracellular calcium measurements as a method in studies on activity of purinergic P2X receptor channels

2003 ◽  
Vol 285 (2) ◽  
pp. C467-C479 ◽  
Author(s):  
Mu-Lan He ◽  
Hana Zemkova ◽  
Taka-aki Koshimizu ◽  
Melanija Tomić ◽  
Stanko S. Stojilkovic
Keyword(s):  
Purinergic Receptors ◽  
Host Cells ◽  
P2x Receptor ◽  
Wild Type ◽  
Hek 293 ◽  
Human Embryonic Kidney Cells ◽  
Voltage Gated ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Intracellular Ca

Extracellular nucleotide-activated purinergic receptors (P2XRs) are a family of cation-permeable channels that conduct small cations, including Ca2+, leading to the depolarization of cells and subsequent stimulation of voltage-gated Ca2+ influx in excitable cells. Here, we studied the spatiotemporal characteristics of intracellular Ca2+ signaling and its dependence on current signaling in excitable mouse immortalized gonadotropin-releasing hormone-secreting cells (GT1) and nonexcitable human embryonic kidney cells (HEK-293) cells expressing wild-type and chimeric P2XRs. In both cell types, P2XR generated depolarizing currents during the sustained ATP stimulation, which desensitized in order (from rapidly desensitizing to nondesensitizing): P2X3R > P2X2b + X4R > P2X2bR > P2X2a + X4R > P2X4R > P2X2aR > P2X7R. HEK-293 cells were not suitable for studies on P2XR-mediated Ca2+ influx because of the coactivation of endogenously expressed Ca2+-mobilizing purinergic P2Y receptors. However, when expressed in GT1 cells, all wild-type and chimeric P2XRs responded to agonist binding with global Ca2+ signals, which desensitized in the same order as current signals but in a significantly slower manner. The global distribution of Ca2+ signals was present independently of the rate of current desensitization. The temporal characteristics of Ca2+ signals were not affected by voltage-gated Ca2+ influx and removal of extracellular sodium. Ca2+ signals reflected well the receptor-specific EC50 values for ATP and the extracellular Zn2+ and pH sensitivities of P2XRs. These results indicate that intracellular Ca2+ measurements are useful for characterizing the pharmacological properties and messenger functions of P2XRs, as well as the kinetics of channel activity, when the host cells do not express other members of purinergic receptors.

Agouti regulation of intracellular calcium: role of melanocortin receptors

1997 ◽  
Vol 272 (3) ◽  
pp. E379-E384 ◽  
Author(s):  
J. H. Kim ◽  
L. L. Kiefer ◽  
R. P. Woychik ◽  
W. O. Wilkison ◽  
A. Truesdale ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Cell Types ◽  
Maximal Response ◽  
Melanocortin Receptors ◽  
Response Curves ◽  
Hek 293 ◽  
Human Embryonic Kidney Cells ◽  
Hek 293 Cells ◽  
293 Cells

Several dominant mutations at the murine agouti locus cause a syndrome of marked obesity and insulin resistance. We have recently reported that intracellular free Ca2+ concentration ([Ca2+]i) is elevated in viable yellow mice. Because [Ca2+]i has a key role in the pathogenesis of insulin resistance, obesity, and hypertension, the role of the purified agouti gene product in regulating [Ca2+]i was evaluated in a number of cell types. Purified murine agouti induced slow, sustained increases in [Ca2+]i in A7r5 vascular smooth muscle cells and 3T3-L1 adipocytes in a dose-dependent fashion. In L6 skeletal myocytes, agouti stimulated an increase in [Ca2+]i with an apparent concentration eliciting 50% of the maximal response (EC50) of 62 nM. This response was substantially inhibited by Ca2+ entry blockade with nitrendipine. To determine whether melanocortin receptors play a role in agouti regulation of [Ca2+]i, we examined the effect of melanocortin peptides and agouti in cells stably transfected with human melanocortin receptors. Human embryonic kidney cells (HEK-293 cells) transfected with either the human melanocortin 1 receptor (MC1R) or melanocortin 3 receptor responded to human agouti with slow, sustained increases in [Ca2+]i, whereas nontransfected HEK-293 cells with no melanocortin receptors did not respond to agouti. Dose-response curves in the MC1R line showed that agouti had an EC50 of 18 nM, which is comparable to that for agouti antagonism of (125)I-Nle,D-Phe-alpha-melanocyte-stimulating hormone binding in the same cell line. This direct effect of agouti on stimulating increases in [Ca2+]i suggests a potential mechanism for agouti-induced insulin resistance.

scholarly journals Multidrug resistance-associated protein 9 (ABCC12) is present in mouse and boar sperm

2007 ◽  
Vol 406 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Nobuhito Ono ◽  
Ingrid Van der Heijden ◽  
George L. Scheffer ◽  
Koen Van de Wetering ◽  
Elizabeth Van Deemter ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Kidney Cells ◽  
Cell Fractionation ◽  
Hek 293 ◽  
Human Embryonic Kidney Cells ◽  
Hek 293 Cells ◽  
Drug Conjugates ◽  
293 Cells ◽  
Boar Sperm ◽  
Alternatively Spliced

The human and murine genes for MRP9 (multidrug resistance-associated protein 9; ABCC12) yield many alternatively spliced RNAs. Using a panel of monoclonal antibodies, we detected full-length Mrp9 only in testicular germ cells and mouse sperm; we obtained no evidence for the existence of the truncated 100 kDa MRP9 protein reported previously. In contrast with other MRPs, neither murine Mrp9 nor the human MRP9 produced in MRP9-transfected HEK-293 cells (human embryonic kidney cells) appears to contain N-linked carbohydrates. In mouse and boar sperm, Mrp9 localizes to the midpiece, a structure containing all sperm mitochondria. However, immunolocalization microscopy and cell fractionation studies with transfected HEK-293 cells and mouse testis show that MRP9/Mrp9 does not localize to mitochondria. In HEK-293 cells, it is predominantly localized in the endoplasmic reticulum. We have been unable to demonstrate transport by MRP9 of substrates transported by other MRPs, such as drug conjugates and other organic anions.

Effect of human acetylcholinesterase subunit assembly on its circulatory residence

2001 ◽  
Vol 354 (3) ◽  
pp. 613-625 ◽  
Author(s):  
Theodor CHITLARU ◽  
Chanoch KRONMAN ◽  
Baruch VELAN ◽  
Avigdor SHAFFERMAN
Keyword(s):  
Laser Desorption Ionization ◽  
Wild Type ◽  
Ionization Time ◽  
Hek 293 ◽  
Enzyme Preparations ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Differential Behaviour ◽  
Oligomeric Forms

Sialylated recombinant human acetylcholinesterase (rHuAChE), produced by stably transfected cells, is composed of a mixed population of monomers, dimers and tetramers and manifests a time-dependent circulatory enrichment of the higher-order oligomeric forms. To investigate this phenomenon further, homogeneous preparations of rHuAChE differing in their oligomerization statuses were generated: (1) monomers, represented by the oligomerization-impaired C580A-rHuAChE mutant, (2) wild-type (WT) dimers and (3) tetramers of WT-rHuAChE generated in vitro by complexation with a synthetic ColQ-derived proline-rich attachment domain (‘PRAD’) peptide. Three different series of each of these three oligoform preparations were produced: (1) partly sialylated, derived from HEK-293 cells; (2) fully sialylated, derived from engineered HEK-293 cells expressing high levels of sialyltransferase; and (3) desialylated, after treatment with sialidase to remove sialic acid termini quantitatively. The oligosaccharides associated with each of the various preparations were extensively analysed by matrix-assisted laser desorption ionization–time-of-flight MS. With the enzyme preparations comprising the fully sialylated series, a clear linear relationship between oligomerization and circulatory mean residence time (MRT) was observed. Thus monomers, dimers and tetramers exhibited MRTs of 110, 195 and 740min respectively. As the level of sialylation decreased, this differential behaviour became less pronounced; eventually, after desialylation all oligoforms had the same MRT (5min). These observations suggest that multiple removal systems contribute to the elimination of AChE from the circulation. Here we also demonstrate that by the combined modulation of sialylation and tetramerization it is possible to generate a rHuAChE displaying a circulatory residence exceeding that of all other known forms of native or recombinant human AChE.

scholarly journals The Role of Endogenous Human Trp4 in Regulating Carbachol-induced Calcium Oscillations in HEK-293 Cells

2002 ◽  
Vol 277 (16) ◽  
pp. 13597-13608 ◽  
Author(s):  
Xiaoyan Wu ◽  
György Babnigg ◽  
Tatiana Zagranichnaya ◽  
Mitchel L. Villereal
Keyword(s):  
Calcium Oscillations ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells

scholarly journals Regulation of apoptosis signal-regulating kinase 1 by protein phosphatase 2Cϵ

2007 ◽  
Vol 405 (3) ◽  
pp. 591-596 ◽  
Author(s):  
Jun-ichi Saito ◽  
Shinnosuke Toriumi ◽  
Kenjiro Awano ◽  
Hidenori Ichijo ◽  
Keiichi Sasaki ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Feedback Regulation ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Regulation Mechanism ◽  
H2o2 Treatment ◽  
Hek 293 ◽  
Human Embryonic Kidney Cells ◽  
Hek 293 Cells ◽  
293 Cells

ASK1 (apoptosis signal-regulating kinase 1), a MKKK (mitogen-activated protein kinase kinase kinase), is activated in response to cytotoxic stresses, such as H2O2 and TNFα (tumour necrosis factor α). ASK1 induction initiates a signalling cascade leading to apoptosis. After exposure of cells to H2O2, ASK1 is transiently activated by autophosphorylation at Thr845. The protein then associates with PP5 (protein serine/threonine phosphatase 5), which inactivates ASK1 by dephosphorylation of Thr845. Although this feedback regulation mechanism has been elucidated, it remains unclear how ASK1 is maintained in the dephosphorylated state under non-stressed conditions. In the present study, we have examined the possible role of PP2Cϵ (protein phosphatase 2Cϵ), a member of PP2C family, in the regulation of ASK1 signalling. Following expression in HEK-293 cells (human embryonic kidney cells), wild-type PP2Cϵ inhibited ASK1-induced activation of an AP-1 (activator protein 1) reporter gene. Conversely, a dominant-negative PP2Cϵ mutant enhanced AP-1 activity. Exogenous PP2Cϵ associated with exogenous ASK1 in HEK-293 cells under non-stressed conditions, inactivating ASK1 by decreasing Thr845 phosphorylation. The association of endogenous PP2Cϵ and ASK1 was also observed in mouse brain extracts. PP2Cϵ directly dephosphorylated ASK1 at Thr845in vitro. In contrast with PP5, PP2Cϵ transiently dissociated from ASK1 within cells upon H2O2 treatment. These results suggest that PP2Cϵ maintains ASK1 in an inactive state by dephosphorylation in quiescent cells, supporting the possibility that PP2Cϵ and PP5 play different roles in H2O2-induced regulation of ASK1 activity.

scholarly journals Role of integrin αVβ3 in the production of recombinant adenoviruses in HEK-293 cells

Gene Therapy ◽  
2002 ◽  
Vol 9 (14) ◽  
pp. 907-914 ◽  
Author(s):  
WLW Ling ◽  
RL Longley ◽  
DL Brassard ◽  
L Armstrong ◽  
EJ Schaefer
Keyword(s):  
Integrin Αvβ3 ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells
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