Extracellular ATP‐dependent activation of plasma membrane Ca<sup>2+</sup> pump in HEK‐293 cells

Qi, Zhi; Murase, Kotono; Obata, Shuichi; Sokabe, Masahiro

doi:10.1038/sj.bjp.0703563

Cited by 19 publications

(13 citation statements)

References 23 publications

(28 reference statements)

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“…Simultaneous activation of the G protein-coupled receptor signaling pathway by carbachol and inhibition of either CaM by calmidazolium or CaMKII by KN-62 had additive effects on ASP ϩ uptake, indicating the independence of the carbachol-mediated inhibition and the CaM-mediated stimulation of hOCT2 transport. Carbachol or ATP increased [Ca 2ϩ ] i in this and previous reports from HEK-293 cells (27,37). This increase in [Ca 2ϩ ] i should have increased CaM activity and, therefore, stimulated hOCT2 transport; however, the opposite was true.…”

Section: Discussioncontrasting

confidence: 42%

“…To investigate the effect of activation of G protein-coupled receptor on ASP ϩ uptake in hOCT2-transfected HEK-293 cells, we used the purinergic agonist ATP and the muscarinic agonist carbachol. Receptors for both agonists have been demonstrated in HEK-293 cells (27,37). ATP and carbachol resulted in inhibition of ASP ϩ uptake by ϳ34 and 44%, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

Çetinkaya

Ciarimboli

Yalçinkaya

et al. 2003

American Journal of Physiology-Renal Physiology

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Properties and regulation of the human organic cation (OC) transporter type 2 (hOCT2) expressed in HEK-293 cells were extensively characterized using the fluorescent OC 4-[4-(dimethylamino)styryl]- N-methylpyridinium (ASP+). ASP+ uptake was electrogenic and inhibited by TPA+ (EC50 = 2.7 μM), tetraethylammonium (EC50 = 35 μM), cimetidine (EC50 = 36 μM), or quinine (EC50 = 6.7 μM). Stimulation with carbachol or ATP decreased initial uptake by 44 ± 3 ( n = 14) and 34 ± 4% ( n = 21), respectively, independently of PKC but dependent on phosphatidylinositol 3-kinase (PI3K). PKA stimulation decreased uptake by 18 ± 4% ( n = 40). Inhibition of calmodulin (CaM), Ca2+/CaM-dependent kinase II, or myosin light chain kinase decreased uptake by 63 ± 2 ( n = 15), 40 ± 4 ( n = 30), and 31 ± 4% ( n = 16), respectively. Inhibition of CaM resulted in a significant change in the EC50 value for the inhibition of ASP+ uptake by tetraethylammonium. In conclusion, we demonstrate that the hOCT2 is inhibited by PI3K and PKA and activated by a CaM-dependent signaling pathway, probably via a change in substrate affinity.

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Section: Discussioncontrasting

confidence: 42%

Section: Discussionmentioning

confidence: 99%

Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

Çetinkaya

Ciarimboli

Yalçinkaya

et al. 2003

American Journal of Physiology-Renal Physiology

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“…2C). This increase in calcium by P2Y receptors upon BzATP application has been previously reported for native HEK-293 cells (23). The addition of 50 M BzATP to HEK-293 cells transfected with the full-length rat P2X7R caused a sustained increase in fluo-4 fluorescence, which was interpreted as an influx of calcium through the P2X7 channel (Fig.…”

Section: Functional Analysis Of Pore Formation and Channel Activity Imentioning

confidence: 87%

P2X7 Receptor Cell Surface Expression and Cytolytic Pore Formation Are Regulated by a Distal C-terminal Region

Smart

Panchal

et al. 2003

Journal of Biological Chemistry

151

171

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The importance of the cytosolic C-terminal region of the P2X7 receptor (P2X7R) is unquestioned, yet little is known about the functional domains of this region and how they may contribute to the numerous properties ascribed to this receptor. A structure-function analysis of truncated and single-residue-mutated P2X7 receptors was performed in HEK-293 cells and Xenopus oocytes. Cells expressing receptors truncated at residue 581 (of 595) have negligible ethidium ion uptake, whereas those expressing the P2X7R truncated at position 582 give wild type ethidium ion uptake suggesting that pore formation requires over 95% of the C-terminal tail. Channel function was evident even in receptors that were truncated at position 380 indicating that only a small portion of the cytosolic region is required for channel activity. Surprisingly, truncations in the region between residues 551 and 581 resulted in non-functional receptors with no detectable cell surface expression in HEK-293 cells. A more detailed analysis revealed that mutations of single residues within this region could also abolish receptor function and cell surface expression, suggesting that this region may participate in regulating the surface expression of the pore-forming P2X7R.

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“…4D). ATP and other agonists have been reported previously to activate the PMCA in HEK293 cells (Qi et al, 2000) and other cell types (Usachev et al, 2002).…”

Section: Resultsmentioning

confidence: 99%

“…2A. The actions of a different PMCA inhibitor, sodium orthovanadate (Qi et al, 2000), are shown in Fig. 2E.…”

Section: Resultsmentioning

confidence: 99%

Evidence that Ca2+ cycling by the plasma membrane Ca2+-ATPase increases the `excitability' of the extracellular Ca2+-sensing receptor

Luisi

Hofer

2003

Journal of Cell Science

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IntroductionThe extracellular Ca 2+ -sensing receptor (CaR) is a cell surface receptor for divalent cations whose existence was originally suspected in the parathyroid gland (Brown et al., 1987;Nemeth and Scarpa, 1987;Shoback et al., 1988). Cloning of the receptor by Brown and colleagues (Brown et al., 1993) confirmed the essential role of CaR as a Ca 2+ sensor in the parathyroid, and also set the stage for the identification of the receptor in a wide variety of tissues not involved in systemic Ca 2+ homeostasis . This seventransmembrane-spanning receptor couples, via heterotrimeric G-proteins, to several different signaling cascades, including the phospholipase C (PLC)/phosphoinositide/Ca 2+ pathway (Brown and MacLeod, 2001). The binding of Ca 2+ to the human parathyroid receptor is known to be a highly cooperative process, making CaR a good Ca 2+ 'increment detector'. Although half-maximal activation of the receptor occurs around 3.5 mM, with maximal stimulation at 5.5 mM (Conigrave et al., 2000a;Quinn et al., 1997), CaR is able to sense small [Ca 2+ ] changes (±0.2 mM) in the physiological range (around 1.8 mM Ca 2+ ).It is important to note that CaR is also stimulated by Mg 2+ and certain polycations [including some endogenous polyamines such as spermine and spermidine (Quinn et al., 1997)]. Synthetic small molecule agonists of the receptor, such as the allosteric modulator NPS R-467 (Nemeth et al., 1998), have also been prepared. Brown and colleagues recently showed that the CaR is activated by physiological concentrations of amino acids [particularly aromatic and small aliphatic L-amino acids (Conigrave et al., 2000b)], and that it is modulated by ionic strength . It is therefore likely that multiple agonists act in concert to stimulate the receptor physiologically.We noted previously that stimulation of CaR with maximal doses of CaR agonists was frequently manifested by an oscillatory Ca 2+ signal in HEK293 cells transfected with the human extracellular Ca 2+ -sensing receptor (HEK CaR cells) (Hofer et al., 2000). The same observation was made in CaRtransfected HEK cells by Breitwieser and Gama (Breitwieser and Gama, 2001), who also reported that Ca 2+ spiking was acutely sensitive to small incremental increases in extracellular [Ca 2+ ]. Such oscillations were sustained for up to 40 minutes, until they gradually diminished in amplitude. Young and Rozengurt recently extended these findings, showing that aromatic amino acids can sensitize the receptor to small incremental increases in external [Ca 2+ ] in HEK CaR cells, producing distinctive patterns of oscillations (Young and Rozengurt, 2002). Native tissues that express CaR endogenously, including parathyroid cells (Miki et al., 1995)

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Extracellular ATP‐dependent activation of plasma membrane Ca²⁺ pump in HEK‐293 cells

Cited by 19 publications

References 23 publications

Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

P2X7 Receptor Cell Surface Expression and Cytolytic Pore Formation Are Regulated by a Distal C-terminal Region

Evidence that Ca2+ cycling by the plasma membrane Ca2+-ATPase increases the `excitability' of the extracellular Ca2+-sensing receptor

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Extracellular ATP‐dependent activation of plasma membrane Ca2+ pump in HEK‐293 cells

Cited by 19 publications

References 23 publications

Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

Regulation of human organic cation transporter hOCT2 by PKA, PI3K, and calmodulin-dependent kinases

P2X7 Receptor Cell Surface Expression and Cytolytic Pore Formation Are Regulated by a Distal C-terminal Region

Evidence that Ca2+ cycling by the plasma membrane Ca2+-ATPase increases the `excitability' of the extracellular Ca2+-sensing receptor

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Extracellular ATP‐dependent activation of plasma membrane Ca²⁺ pump in HEK‐293 cells