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The role of AMPK in regulation of Na +,K +-ATPase in skeletal muscle: does the gauge always plug the sink? J Muscle Res Cell Motil 2021; 42:77-97. [PMID: 33398789 DOI: 10.1007/s10974-020-09594-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 12/14/2020] [Indexed: 12/14/2022]
Abstract
AMP-activated protein kinase (AMPK) is a cellular energy gauge and a major regulator of cellular energy homeostasis. Once activated, AMPK stimulates nutrient uptake and the ATP-producing catabolic pathways, while it suppresses the ATP-consuming anabolic pathways, thus helping to maintain the cellular energy balance under energy-deprived conditions. As much as ~ 20-25% of the whole-body ATP consumption occurs due to a reaction catalysed by Na+,K+-ATPase (NKA). Being the single most important sink of energy, NKA might seem to be an essential target of the AMPK-mediated energy saving measures, yet NKA is vital for maintenance of transmembrane Na+ and K+ gradients, water homeostasis, cellular excitability, and the Na+-coupled transport of nutrients and ions. Consistent with the model that AMPK regulates ATP consumption by NKA, activation of AMPK in the lung alveolar cells stimulates endocytosis of NKA, thus suppressing the transepithelial ion transport and the absorption of the alveolar fluid. In skeletal muscles, contractions activate NKA, which opposes a rundown of transmembrane ion gradients, as well as AMPK, which plays an important role in adaptations to exercise. Inhibition of NKA in contracting skeletal muscle accentuates perturbations in ion concentrations and accelerates development of fatigue. However, different models suggest that AMPK does not inhibit or even stimulates NKA in skeletal muscle, which appears to contradict the idea that AMPK maintains the cellular energy balance by always suppressing ATP-consuming processes. In this short review, we examine the role of AMPK in regulation of NKA in skeletal muscle and discuss the apparent paradox of AMPK-stimulated ATP consumption.
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Cordeiro ER, Filetti FM, Simões MR, Vassallo DV. Mercury induces nuclear estrogen receptors to act as vasoconstrictors promoting endothelial denudation via the PI3K/Akt signaling pathway. Toxicol Appl Pharmacol 2019; 381:114710. [PMID: 31415774 DOI: 10.1016/j.taap.2019.114710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/29/2019] [Accepted: 08/10/2019] [Indexed: 10/26/2022]
Abstract
Cardiovascular diseases (CVD) are more frequent among postmenopausal women due to the decline of estrogen concentration in plasma. However, the role of the vascular modulator effect of estrogen is controversial, since it occurs both in physiological and pathological conditions, increasing or reducing vascular reactivity. As mercury is widely associated with the development of CVD, we investigated putative hazardous effects on the mechanisms that modulate vascular reactivity in aortic rings of female Wistar rats promoted by acute mercury exposure. Mercury increased vascular reactivity and oxidative stress possibly due to NADPH oxidase participation, increased production of cyclooxygenase-2 (COX-2) and thromboxane A2 (TXA2) formation. The metal also induced endothelial denudation in the aorta by reducing the bioavailability of nitric oxide (NO) and enhancing the activity of the PI3K/Akt signaling pathway. Mercury exposure also induced nuclear estrogen receptors (ERα, ERβ) to act as vasoconstrictors. Our findings suggest that mercury might increase the chances of developing cardiovascular diseases in females and should be considered an important environmental risk factor.
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Affiliation(s)
- Evellyn Rodrigues Cordeiro
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Filipe Martinuzo Filetti
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Maylla Ronacher Simões
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Dalton Valentim Vassallo
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil; Health Science Center of Vitória-EMESCAM, Vitória, ES CEP 29045-402, Brazil.
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Liu J, Yan Y, Nie Y, Shapiro JI. Na/K-ATPase Signaling and Salt Sensitivity: The Role of Oxidative Stress. Antioxidants (Basel) 2017; 6:E18. [PMID: 28257114 PMCID: PMC5384181 DOI: 10.3390/antiox6010018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 02/10/2017] [Accepted: 02/22/2017] [Indexed: 02/07/2023] Open
Abstract
Other than genetic regulation of salt sensitivity of blood pressure, many factors have been shown to regulate renal sodium handling which contributes to long-term blood pressure regulation and have been extensively reviewed. Here we present our progress on the Na/K-ATPase signaling mediated sodium reabsorption in renal proximal tubules, from cardiotonic steroids-mediated to reactive oxygen species (ROS)-mediated Na/K-ATPase signaling that contributes to experimental salt sensitivity.
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Affiliation(s)
- Jiang Liu
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Yanling Yan
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Ying Nie
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA.
| | - Joseph I Shapiro
- Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25701, USA
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Diederich M, Muller F, Cerella C. Cardiac glycosides: From molecular targets to immunogenic cell death. Biochem Pharmacol 2017; 125:1-11. [DOI: 10.1016/j.bcp.2016.08.017] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Accepted: 08/15/2016] [Indexed: 11/26/2022]
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Akimova OA, Kapilevich LV, Orlov SN, Lopina OD. Identification of Proteins Whose Interaction with Na+,K+-ATPase Is Triggered by Ouabain. BIOCHEMISTRY (MOSCOW) 2017; 81:1013-22. [PMID: 27682173 DOI: 10.1134/s0006297916090108] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Prolonged exposure of different epithelial cells (canine renal epithelial cells (MDCK), vascular endothelial cells from porcine aorta (PAEC), human umbilical vein endothelial cells (HUVEC), cervical adenocarcinoma (HeLa), as well as epithelial cells from colon carcinoma (Caco-2)) with ouabain or with other cardiotonic steroids was shown earlier to result in the death of these cells. Intermediates in the cell death signal cascade remain unknown. In the present study, we used proteomics methods for identification of proteins whose interaction with Na+,K+-ATPase is triggered by ouabain. After exposure of Caco-2 human colorectal adenocarcinoma cells with 3 µM of ouabain for 3 h, the protein interacting in complex with Na+,K+-ATPase was coimmunoprecipitated using antibodies against the enzyme α1-subunit. Proteins of coimmunoprecipitates were separated by 2D electrophoresis in polyacrylamide gel. A number of proteins in the coimmunoprecipitates with molecular masses of 71-74, 46, 40-43, 38, and 33-35 kDa was revealed whose binding to Na+,K+-ATPase was activated by ouabain. Analyses conducted by mass spectroscopy allowed us to identify some of them, including seven signal proteins from superfamilies of glucocorticoid receptors, serine/threonine protein kinases, and protein phosphatases 2C, Src-, and Rho-GTPases. The possible participation of these proteins in activation of cell signaling terminated by cell death is discussed.
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Affiliation(s)
- O A Akimova
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119991, Russia.
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6
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Liu T, Konkalmatt PR, Yang Y, Jose PA. Gastrin decreases Na+,K+-ATPase activity via a PI 3-kinase- and PKC-dependent pathway in human renal proximal tubule cells. Am J Physiol Endocrinol Metab 2016; 310:E565-71. [PMID: 26786777 PMCID: PMC4824137 DOI: 10.1152/ajpendo.00360.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 01/08/2016] [Indexed: 12/31/2022]
Abstract
The natriuretic effect of gastrin suggests a role in the coordinated regulation of sodium balance by the gastrointestinal tract and the kidney. The renal molecular targets and signal transduction pathways for such an effect of gastrin are largely unknown. Recently, we reported that gastrin induces NHE3 phosphorylation and internalization via phosphatidylinositol (PI) 3-kinase and PKCα. In this study, we show that gastrin induced the phosphorylation of human Na(+),K(+)-ATPase at serine 16, resulting in its endocytosis via Rab5 and Rab7 endosomes. The gastrin-stimulated phosphorylation of Na(+),K(+)-ATPase was dependent on PI 3-kinase because the phosphorylation was blocked by the PI 3-kinase inhibitor wortmannin. The phosphorylation of Na(+),K(+)-ATPase was also blocked by chelerythrine, a pan-PKC inhibitor, Gö-6976, a conventional PKC (cPKC) inhibitor, and BAPTA-AM, an intracellular calcium chelator, suggesting the importance of cPKC and intracellular calcium in the gastrin signaling pathway. The gastrin-mediated phosphorylation of Na(+),K(+)-ATPase was also inhibited by U-73122, a phospholipase C (PLC) inhibitor. These results suggest that gastrin regulates sodium hydrogen exchanger and pump in renal proximal tubule cells at the apical and basolateral membranes.
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Affiliation(s)
- Tianbing Liu
- Center for Molecular Physiology Research, Children's Research Institute, Children's National Medical Center, Washington, DC
| | - Prasad R Konkalmatt
- Departments of Medicine and Physiology, University of Maryland School of Medicine, Baltimore, Maryland; Division of Renal Diseases and Hypertension, Department of Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC; and
| | - Yu Yang
- Center for Molecular Physiology Research, Children's Research Institute, Children's National Medical Center, Washington, DC; Departments of Medicine and Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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Zhang LN, Li JX, Hao L, Sun YJ, Xie YH, Wu SM, Liu L, Chen XL, Gao ZB. Crosstalk between dopamine receptors and the Na⁺/K⁺-ATPase (review). Mol Med Rep 2013; 8:1291-9. [PMID: 24065247 DOI: 10.3892/mmr.2013.1697] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 09/05/2013] [Indexed: 11/06/2022] Open
Abstract
Dopamine (DA) receptors, which belong to the G protein-coupled receptor family, are the target of ~50% of all modern medicinal drugs and constitute a large and diverse class of proteins whose primary function is to transduce extracellular stimuli into intracellular signals. Na+/K+-ATPase (NKA) is ubiquitous and crucial for the maintenance of intracellular ion homeostasis and excitability. Furthermore, it plays a critical role in diverse effects, including clinical cardiotonic and cardioprotective effects, ischemic preconditioning in the brain, natriuresis, lung edema clearance and other processes. NKA regulation is of physiological and pharmacological importance and has species- and tissue-specific variations. The activation of DA receptors regulates NKA expression/activity and trafficking in various tissues and cells, for example in the kidney, lung, intestine, brain, non-pigmented ciliary epithelium and the vascular bed. DA receptor-mediated regulation of NKA mediates a diverse range of cellular responses and includes endocytosis/exocytosis, phosphorylation/dephosphorylation of the α subunit of NKA and multiple signaling pathways, including phosphatidylinositol (PI)-phospholipase C/protein kinase (PK) C, cAMP/PKA, PI3K, adaptor protein 2, tyrosine phosphatase and mitogen-activated protein kinase/extracellular signal-regulated protein kinase. Furthermore, in brain and HEK293T cells, D1 and D2 receptors exist in a complex with NKA. Among D1 and D2 receptors and NKA, regulations are reciprocal, which leads to crosstalk between DA receptors and NKA. In the present study, the current understanding of signaling mechanisms responsible for the crosstalk between DA receptors and NKA, as well as with specific consequent functions, is reviewed.
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Affiliation(s)
- Li-Nan Zhang
- Department of Pharmacy, College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, P.R. China
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Bełtowski J. Leptin and the Regulation of Renal Sodium Handling and Renal Na-Transporting ATPases: Role in the Pathogenesis of Arterial Hypertension. Curr Cardiol Rev 2011; 6:31-40. [PMID: 21286276 PMCID: PMC2845792 DOI: 10.2174/157340310790231644] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 08/03/2009] [Accepted: 08/03/2009] [Indexed: 12/13/2022] Open
Abstract
Leptin, an adipose tissue hormone which regulates food intake, is also involved in the pathogenesis of arterial hypertension. Plasma leptin concentration is increased in obese individuals. Chronic leptin administration or transgenic overexpression increases blood pressure in experimental animals, and some studies indicate that plasma leptin is elevated in hypertensive subjects independently of body weight. Leptin has a dose- and time-dependent effect on urinary sodium excretion. High doses of leptin increase Na(+) excretion in the short run; partially by decreasing renal Na(+),K(+)-ATPase (sodium pump) activity. This effect is mediated by phosphatidylinositol 3-kinase (PI3K) and is impaired in animals with dietary-induced obesity. In contrast to acute, chronic elevation of plasma leptin to the level observed in patients with the metabolic syndrome impairs renal Na(+) excretion, which is associated with the increase in renal Na(+),K(+)-ATPase activity. This effect results from oxidative stress-induced deficiency of nitric oxide and/or transactivation of epidermal growth factor receptor and subsequent stimulation of extracellular signal-regulated kinases. Ameliorating "renal leptin resistance" or reducing leptin level and/or leptin signaling in states of chronic hyperleptinemia may be a novel strategy for the treatment of arterial hypertension associated with the metabolic syndrome.
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Affiliation(s)
- Jerzy Bełtowski
- Dept. of Pathophysiology, Medical University, Lublin, Poland
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Karpova LV, Akkuratov EE, Brodskaya OM, Boldyrev AA. The Na+ pump and intracellular signaling mechanisms. Biophysics (Nagoya-shi) 2011. [DOI: 10.1134/s0006350910060096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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11
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Basevich EV, Lopina OD, Rubtsov AM. Seasonal changes in microsomal fraction enriched with Na,K-ATPase from kidneys of the ground squirrel Spermophilus undulatus. BIOCHEMISTRY (MOSCOW) 2011; 75:1408-16. [PMID: 21314610 DOI: 10.1134/s0006297910110143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The Na,K-ATPase activity in microsomal fraction isolated from kidneys of winter hibernating ground squirrels was found to be 1.8-2.0-fold lower than that in active animals in summer. This is partially connected with a decrease in Na,K-ATPase protein content in these preparations (by 25%). Using antibodies to different isoforms of Na,K-ATPase α-subunit and analysis of enzyme inhibition by ouabain, it was found that the decrease in Na,K-ATPase activity during hibernation is not connected with change in isoenzyme composition. Seasonal changes of Na,K-ATPase α-subunit phosphorylation level by endogenous protein kinases were not found. Proteins which could be potential regulators of Na,K-ATPase activity were not found among phosphorylated proteins of the microsomes. Analysis of the composition and properties of the lipid phase of microsomes showed that the total level of unsaturation of fatty acids and the lipid/protein ratio are not changed significantly during hibernation, whereas the cholesterol content in preparations from kidneys of hibernating ground squirrels is approximately twice higher than that in preparations from kidneys of active animals. However, using spin and fluorescent probes it was shown that this difference in cholesterol content does not affect the integral membrane microviscosity of microsomes. Using the cross-linking agent cupric phenanthroline, it was shown that Na,K-ATPase in membranes of microsomes from kidneys of hibernating ground squirrels is present in more aggregated state in comparison with membranes of microsomes from kidneys of active animals. We suggest that the decrease in Na,K-ATPase activity in kidneys of ground squirrels during hibernation is mainly connected with the aggregation of proteins in plasma membrane.
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Affiliation(s)
- E V Basevich
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow 119991, Russia.
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Zhang L, Guo F, Guo H, Wang H, Zhang Z, Liu X, Shi X, Gou X, Su Q, Yin J, Wang Y. The paradox of dopamine and angiotensin II-mediated Na(+), K(+)-ATPase regulation in renal proximal tubules. Clin Exp Hypertens 2011; 32:464-8. [PMID: 21029011 DOI: 10.3109/10641963.2010.496516] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Accumulated studies reported that the natruretic dopamine (DA) and the anti-natruretic angiotensin II (Ang II) represent an important mechanism to regulate renal Na(+) and water excretion through intracellular secondary messengers to inhibit or activate renal proximal tubule (PT) Na(+), K(+)-ATPase (NKA). The antagonistic actions were mediated by the phosphorylation of different position of NKA α₁-subunit and different Pals-associated tight junction protein (PATJ) PDZ domains, the different protein kinase C (PKC) isoforms (PKC-β, PKC-ζ), the common adenylyl cyclase (AC) pathway, and the crosstalk and balance between DA and Ang II to NKA regulation. Besides, Ang II-mediated NKA modulation has bi-phasic effects.
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Affiliation(s)
- Linan Zhang
- Pharmacy Department, Hebei University of Science and Technology, Hebei, China.
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Zhuang Z, Marshansky V, Breton S, Brown D. Is caveolin involved in normal proximal tubule function? Presence in model PT systems but absence in situ. Am J Physiol Renal Physiol 2010; 300:F199-206. [PMID: 20980408 DOI: 10.1152/ajprenal.00513.2010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Kidney proximal tubule (PT) cells are specialized for the uptake and transport of ions, solutes, peptides, and proteins. These functions are often regulated by hormones that signal at the cell surface and are internalized by clathrin-mediated endocytosis. However, the caveolin/caveolae pathway has also been implicated in normal PT function, often based on data from isolated PTs or PT cells in culture. Although we reported previously that caveolae and caveolin 1 are not detectable in PTs in vivo, reports of caveolin expression and function in PT cells appear periodically in the literature. Therefore, we reexamined caveolin expression in PTs in vivo, in isolated "purified" PTs following collagenase digestion, and in cultured PT cells. Caveolin 1 and 2 protein, mRNA, or immunofluorescence was undetectable in PTs in vivo, but PT cell cultures expressed caveolin 1 and/or 2. Furthermore, caveolin 1 and 2 mRNAs were detected in isolated PTs along with the endothelial markers CD31 and ICAM1. In contrast, no caveolin or endothelial marker mRNAs were detectable in samples isolated from snap-frozen kidneys by laser cut microdissection, which eliminates contamination by other cell types. We conclude 1) caveolin 1 and 2 are not normally expressed by PT cells in situ, 2) caveolin expression is "activated" in cultured PT cells, 3) contamination with non-PT, caveolin-expressing cells is a potential source of caveolin 1 and 2 that must be taken into account when isolated PTs are used in studies to correlate expression of these proteins with PT function.
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Affiliation(s)
- Zhenjie Zhuang
- Massachusetts General Hospital, Center for Systems Biology, Simches Research Bldg., Massachusetts General Hospital and Harvard Medical School, 185 Cambridge St., CPZN 8150, Boston, MA 02114, USA
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Scapin S, Leoni S, Spagnuolo S, Gnocchi D, De Vito P, Luly P, Pedersen JZ, Incerpi S. Short-term effects of thyroid hormones during development: Focus on signal transduction. Steroids 2010; 75:576-84. [PMID: 19900468 DOI: 10.1016/j.steroids.2009.10.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 10/21/2009] [Accepted: 10/28/2009] [Indexed: 12/27/2022]
Abstract
Extranuclear or nongenomic effects of thyroid hormones are mediated by receptors located at the plasma membrane or inside cells, and are independent of protein synthesis. Recently the alphaVbeta3 integrin was identified as a cell membrane receptor for thyroid hormones, and a wide variety of nongenomic effects have now been shown to be induced through binding of thyroid hormones to this receptor. However, also other thyroid hormone receptors can produce nongenomic effects, including the cytoplasmic TRalpha and TRbeta receptors and probably also a G protein-coupled membrane receptor, and increasing importance is now given to thyroid hormone metabolites like 3,5-diiodothyronine and reverse T(3) that can mimick some nongenomic effects of T(3) and T(4). Signal transduction from the alphaVbeta3 integrin may proceed through at least three independent pathways (protein kinase C, Src or mitogen-activated kinases) but the details are still unknown. Thyroid hormones induce nongenomic effects on at least three important Na(+)-dependent transport systems, the Na(+)/K(+)-ATPase, the Na(+)/H(+) exchanger, and amino acid transport System A, leading to a mitogenic response in embryo cells; but modulation of the same transport systems may have different roles in other cells and at different developmental stages. It seems that thyroid hormones in many cases can modulate nongenomically the same targets affected by the nuclear receptors through long-term mechanisms. Recent results on nongenomic effects confirm the old theory that the primary role of thyroid hormones is to keep the steady-state level of functioning of the cell, but more and more mechanisms are discovered by which this goal can be achieved.
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Affiliation(s)
- Sergio Scapin
- Department of Cellular and Developmental Biology, Sapienza University, 00185 Rome, Italy
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15
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Crambert S, Sjöberg A, Eklöf AC, Ibarra F, Holtbäck U. Prolactin and dopamine 1-like receptor interaction in renal proximal tubular cells. Am J Physiol Renal Physiol 2010; 299:F49-54. [PMID: 20462969 DOI: 10.1152/ajprenal.00582.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prolactin is a natriuretic hormone and acts by inhibiting the activity of renal tubular Na(+)-K(+)-ATPase activity. These effects require an intact renal dopamine system. Here, we have studied by which mechanism prolactin and dopamine interact in Sprague-Dawley rat renal tissue. Na(+)-K(+)-ATPase activity was measured as ouabain-sensitive ATP hydrolysis in microdissected renal proximal tubular segments. Intracellular signaling pathways were studied by a variety of different techniques, including Western blotting using phosphospecific antibodies, immunoprecipitation, and biotinylation assays. We found that dopamine and prolactin regulated Na(+)-K(+)-ATPase activity via similar signaling pathways, including protein kinase A, protein kinase C, and phosphoinositide 3-kinase activation. The cross talk between prolactin and dopamine 1-like receptors was explained by a heterologous recruitment of dopamine 1-like receptors to the plasma membrane in renal proximal tubular cells. Prolactin had no effect on Na(+)-K(+)-ATPase activity in spontaneously hypertensive rats, a rat strain with a blunted response to dopamine. These results further emphasize the central role of the renal dopamine system in the interactive regulation of renal tubular salt balance.
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Affiliation(s)
- Susanne Crambert
- Pediatric Unit, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
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Poulsen H, Morth P, Egebjerg J, Nissen P. Phosphorylation of the Na+,K+-ATPase and the H+,K+-ATPase. FEBS Lett 2010; 584:2589-95. [PMID: 20412804 DOI: 10.1016/j.febslet.2010.04.035] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 04/13/2010] [Indexed: 01/11/2023]
Abstract
Phosphorylation is a widely used, reversible means of regulating enzymatic activity. Among the important phosphorylation targets are the Na(+),K(+)- and H(+),K(+)-ATPases that pump ions against their chemical gradients to uphold ionic concentration differences over the plasma membrane. The two pumps are very homologous, and at least one of the phosphorylation sites is conserved, namely a cAMP activated protein kinase (PKA) site, which is important for regulating pumping activity, either by changing the cellular distribution of the ATPases or by directly altering the kinetic properties as supported by electrophysiological results presented here. We further review the other proposed pump phosphorylations.
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Affiliation(s)
- Hanne Poulsen
- Danish National Research Foundation, Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Aarhus University, Department of Molecular Biology, Denmark.
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Karpova LV, Bulygina ER, Boldyrev AA. Different neuronal Na+/K+-ATPase isoforms are involved in diverse signaling pathways. Cell Biochem Funct 2010; 28:135-41. [DOI: 10.1002/cbf.1632] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Zhang L, Zhang Z, Guo H, Wang Y. Na+/K+-ATPase-mediated signal transduction and Na+/K+-ATPase regulation. Fundam Clin Pharmacol 2009; 22:615-21. [PMID: 19049666 DOI: 10.1111/j.1472-8206.2008.00620.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A number of studies suggest that Na(+)/K(+)-ATPase in caveolae interacts with neighboring membrane proteins and organizes cytosolic cascades of signaling proteins to send messages to intracellular organelles in different tissues, mostly in cardiac myocytes. Low concentration of ouabain binding to Na(+)/K(+)-ATPase activates Src/epidermal growth factor receptor complex to initiate multiple signal pathways, which include PLC/IP3/CICR, PI3K, reactive oxygen species (ROS), PLC/DG/PKC/Raf/MEK/ERK1/2, and Ras/Raf/MEK/ERK1/2 pathways. In cardiac myocytes, the resulting downstream events include the induction of some early response proto-oncogenes, activation of transcription factors, activator protein-1, and nuclear factor-kappaB, the regulation of a number of cardiac growth-related genes, and the stimulation of protein synthesis and myocyte hypertrophy and apoptosis. Conversely, several factors acting through signal pathways, such as protein kinases, Ca(2+), ROS, etc., can modulate the activity of the Na(+)/K(+)-ATPase.
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Affiliation(s)
- Linan Zhang
- Department of Pharmacology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang City, Hebei Province, China
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19
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Scapin S, Leoni S, Spagnuolo S, Fiore AM, Incerpi S. Short-term effects of thyroid hormones on Na+-K+-ATPase activity of chick embryo hepatocytes during development: focus on signal transduction. Am J Physiol Cell Physiol 2009; 296:C4-12. [DOI: 10.1152/ajpcell.90604.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nongenomic effects of thyroid hormones on Na+-K+-ATPase activity were studied in chick embryo hepatocytes at two different developmental stages, 14 and 19 days of embryonal age, and the signal transduction pathways involved were characterized. Our data showed the following. 1) 3,5,3′-Triiodo-l-thyronine (T3) and 3,5-diiodo-l-thyronine (3,5-T2) rapidly induced a transient inhibitory effect on the Na+-K+-ATPase; the extent and duration depended on the developmental age of the cells. 2) 3,5-T2behaved as a true hormone and fully mimicked the effect of T3. 3) Thyroxine had no effect at any of the developmental stages. 4) The inhibition of Na+-K+-ATPase was mediated by activation of protein kinase A, protein kinase C, and phosphoinositide 3-kinase, suggesting several modes of modulation of ATPase activity through phosphorylation at different sites. 5) The MAPK pathway did not seem to be involved in the early phase of hormone treatment. 6) The nonpermeant analog T3-agarose inhibited Na+-K+-ATPase activity in the same way as T3, confirming that hormone signaling initiated at a receptor on the plasma membrane. From these results, it can be concluded that the cell response mechanisms change rapidly and drastically within the early phase of embryo growth. The differences found at the two stages probably reflect the different roles of thyroid hormones during development and differentiation.
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Feldmann T, Glukmann V, Medvenev E, Shpolansky U, Galili D, Lichtstein D, Rosen H. Role of endosomal Na+-K+-ATPase and cardiac steroids in the regulation of endocytosis. Am J Physiol Cell Physiol 2007; 293:C885-96. [PMID: 17553933 DOI: 10.1152/ajpcell.00602.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plasma membrane Na(+)-K(+)-ATPase, which drives potassium into and sodium out of the cell, has important roles in numerous physiological processes. Cardiac steroids (CS), such as ouabain and bufalin, specifically interact with the pump and affect ionic homeostasis, signal transduction, and endocytosed membrane traffic. CS-like compounds are present in mammalian tissues, synthesized in the adrenal gland, and considered to be new family of steroid hormones. In this study, the mechanism of Na(+)-K(+)-ATPase involvement in the regulation of endocytosis is explored. We show that the effects of various CS on changes in endosomal pH are mediated by the pump and correspond to their effects on endosomal membrane traffic. In addition, it was found that CS-induced changes in endocytosed membrane traffic were dependent on alterations in [Na(+)] and [H(+)] in the endosome. Furthermore, we show that various CS differentially regulate endosomal pH and membrane traffic. The results suggest that these differences are due to specific binding characteristics. Based on our observations, we propose that Na(+)-K(+)-ATPase is a key player in the regulation of endosomal pH and endocytosed membrane traffic. Furthermore, our results raise the possibility that CS-like hormones regulate differentially intracellular membrane traffic.
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Affiliation(s)
- Tomer Feldmann
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute of Microbiology, The Hebrew Univ.-Hadassah Medical School, Jerusalem 91120, Israel.
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Efendiev R, Das-Panja K, Cinelli AR, Bertorello AM, Pedemonte CH. Localization of intracellular compartments that exchange Na,K-ATPase molecules with the plasma membrane in a hormone-dependent manner. Br J Pharmacol 2007; 151:1006-13. [PMID: 17533417 PMCID: PMC2042937 DOI: 10.1038/sj.bjp.0707304] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND AND PURPOSE Dopamine is a major regulator of sodium reabsorption in proximal tubule epithelia. By binding to D1-receptors, dopamine induces endocytosis of plasma membrane Na,K-ATPase, resulting in a reduced capacity of the cells to transport sodium, thus contributing to natriuresis. We have previously demonstrated several aspects of the molecular mechanism by which dopamine induces Na,K-ATPase endocytosis; however, the location of intracellular compartments containing Na,K-ATPase molecules has not been identified. EXPERIMENTAL APPROACH In this study, we used different approaches to determine the localization of Na,K-ATPase-containing intracellular compartments. By expression of fluorescent-tagged Na,K-ATPase molecules in opossum kidney cells, a cell culture model of proximal tubule epithelia, we used fluorescence microscopy to determine cellular distribution of the fluorescent molecules and the effects of dopamine on this distribution. By labelling cell surface Na,K-ATPase molecules from the cell exterior with either biotin or an epitope-tagged antibody, we determined the localization of the tagged Na,K-ATPase molecules after endocytosis induced by dopamine. KEY RESULTS In cells expressing fluorescent-tagged Na,K-ATPase molecules, there were intracellular compartments containing Na,K-ATPase molecules. These compartments were in very close proximity to the plasma membrane. Upon treatment of the cells with dopamine, the fluorescence labelling of these compartments was increased. The labelling of these compartments was also observed when the endocytosis of biotin- or antibody-tagged plasma membrane Na,K-ATPase molecules was induced by dopamine. CONCLUSIONS AND IMPLICATIONS The intracellular compartments containing Na,K-ATPase molecules are located just underneath the plasma membrane.
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Affiliation(s)
- R Efendiev
- College of Pharmacy, University of Houston, 4800 Calhoun Road, Houston, TX 77204, USA.
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22
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Rosskopf D, Schürks M, Rimmbach C, Schäfers R. Genetics of arterial hypertension and hypotension. Naunyn Schmiedebergs Arch Pharmacol 2007; 374:429-69. [PMID: 17262198 DOI: 10.1007/s00210-007-0133-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 12/22/2006] [Indexed: 01/13/2023]
Abstract
Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.
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Affiliation(s)
- Dieter Rosskopf
- Department Pharmacology, Research Center for Pharmacology and Experimental Therapeutics, Ernst-Moritz-Arndt-University Greifswald, Friedrich Loeffler Str. 23d, 17487 Greifswald, Germany.
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23
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Yuan X, Luo S, Lin Z, Wu Y. Cyclic stretch translocates the alpha2-subunit of the Na pump to plasma membrane in skeletal muscle cells in vitro. Biochem Biophys Res Commun 2006; 348:750-7. [PMID: 16893515 DOI: 10.1016/j.bbrc.2006.07.120] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 07/21/2006] [Indexed: 10/24/2022]
Abstract
The Na+-K+-ATPase and its regulation is important for maintaining membrane potential and transmembrane Na(+) gradient in all skeletal muscle cells and thus is essential for cell survival and function. In our previous study, cyclic stretch activated the Na pump in cultured skeletal muscle cells. Presently, we investigated whether this stimulation was the result of translocation of Na+-K+-ATPase from endosomes to the plasma membrane, and also evaluated the role of phosphatidylinositol 3-kinase (PI 3-kinase), the activation of which initiated vesicular trafficking and targeting of proteins to specific cell compartments. Skeletal muscle cells were stretched at 25% elongation continuous for 24h using the Flexercell Strain Unit. The plasma membrane and endosome fractions were isolated and Western blotted to localize the Na+-K+-ATPase alpha1- and alpha2-subunit protein. The results showed stretch increased Na+-K+-ATPase alpha1- and alpha2-subunit protein expression in plasma membrane fractions and decreased it in endosomes. The alpha2-subunit had a more dynamic response to mechanical stretch. PI 3-kinase inhibitors (LY294002) blocked the stretch-induced translocation of the Na+-K+-ATPase alpha2-subunit, while LY294002 had no effect on the transfer of alpha1-subunit. We concluded that cyclic stretch mainly stimulated the translocation of the alpha2-subunit of Na+-K+-ATPase from endosomes to the plasma membrane via a PI 3-kinase-dependent mechanism in cultured skeletal muscle cells in vitro, which in turn increased the activity of the Na pump.
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Affiliation(s)
- Xiao Yuan
- Department of Orthodontics, The 4th Military Medical University, Xi'an, Shanxi Province 710032, People's Republic of China.
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24
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Kotova O, Al-Khalili L, Talia S, Hooke C, Fedorova OV, Bagrov AY, Chibalin AV. Cardiotonic Steroids Stimulate Glycogen Synthesis in Human Skeletal Muscle Cells via a Src- and ERK1/2-dependent Mechanism. J Biol Chem 2006; 281:20085-94. [PMID: 16714287 DOI: 10.1074/jbc.m601577200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The cardiotonic steroid, ouabain, a specific inhibitor of Na(+),K(+)-ATPase, initiates protein-protein interactions that lead to an increase in growth and proliferation in different cell types. We explored the effects of ouabain on glucose metabolism in human skeletal muscle cells (HSMC) and clarified the mechanisms of ouabain signal transduction. In HSMC, ouabain increased glycogen synthesis in a concentration-dependent manner reaching the maximum at 100 nM. The effect of ouabain was additive to the effect of insulin and was independent of phosphatidylinositol 3-kinase inhibitor LY294002 but was abolished in the presence of a MEK1/2 inhibitor (PD98059) or a Src inhibitor (PP2). Ouabain increased Src-dependent tyrosine phosphorylation of alpha(1)- and alpha(2)-subunits of Na(+),K(+)-ATPase and promoted interaction of alpha(1)- and alpha(2)-subunits with Src, as assessed by co-immunoprecipitation with Src. Phosphorylation of ERK1/2 and GSK3alpha/beta, as well as p90rsk activity, was increased in response to ouabain in HSMC, and these responses were prevented in the presence of PD98059 and PP2. Incubation of HSMC with 100 nM ouabain increased phosphorylation of the alpha-subunits of the Na-pump at a MAPK-specific Thr-Pro motif. Ouabain treatment decreased the surface abundance of alpha(2)-subunit, whereas abundance of the alpha(1)-subunit was unchanged. Marinobufagenin, an endogenous vertebrate bufadienolide cardiotonic steroid, increased glycogen synthesis in HSMC at 10 nM concentration, similarly to 100 nM ouabain. In conclusion, ouabain and marinobufagenin stimulate glycogen synthesis in skeletal muscle. This effect is mediated by activation of a Src-, ERK1/2-, p90rsk-, and GSK3-dependent signaling pathway.
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Affiliation(s)
- Olga Kotova
- Section of Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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Abstract
Leptin is a 16-kDa protein secreted by white adipose tissue that is primarily involved in the regulation of food intake and energy expenditure. Plasma leptin concentration is proportional to the amount of adipose tissue and is markedly increased in obese individuals. Recent studies suggest that leptin is involved in cardiovascular complications of obesity, including arterial hypertension. Acutely administered leptin has no effect on blood pressure, probably because it concomitantly stimulates the sympathetic nervous system and counteracting depressor mechanisms such as natriuresis and nitric oxide (NO)-dependent vasorelaxation. By contrast, chronic hyperleptinemia increases blood pressure because these acute depressor effects are impaired and/or additional sympathetic nervous system-independent pressor effects appear, such as oxidative stress, NO deficiency, enhanced renal Na reabsorption and overproduction of endothelin. Although the cause-effect relationship between leptin and high blood pressure in humans has not been demonstrated directly, many clinical studies have shown elevated plasma leptin in patients with essential hypertension and a significant positive correlation between leptin and blood pressure independent of body adiposity both in normotensive and in hypertensive individuals. In addition, leptin may contribute to end-organ damage in hypertensive individuals such as left ventricular hypertrophy, retinopathy and nephropathy, independent of regulating blood pressure. Here, current knowledge about the role of leptin in the regulation of blood pressure and in the pathogenesis of arterial hypertension is presented.
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Affiliation(s)
- Jerzy Bełtowski
- Department of Pathophysiology, Medical University, Lublin, Poland.
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Bertorello AM, Sznajder JI. The dopamine paradox in lung and kidney epithelia: sharing the same target but operating different signaling networks. Am J Respir Cell Mol Biol 2005; 33:432-7. [PMID: 16234332 PMCID: PMC2715350 DOI: 10.1165/rcmb.2005-0297tr] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Stimulation of dopamine receptors in the lung or kidney epithelia has distinct and opposite effects on the function of Na,K-ATPase, which results in increased Na(+) absorption across the alveolar epithelium and increased sodium excretion via the kidney epithelium. In the lung, dopamine increases Na,K-ATPase by increasing cell basolateral surface expression of Na(+),K(+)-ATPase molecules, whereas in the kidney epithelia it decreases Na(+),K(+)-ATPase activity by removing active units from the plasma membrane by endocytosis. The opposite effects of dopamine over the same target (the Na(+),K(+)-ATPase) involve the activation of a distinct signaling network that it is target specific, and has a different spatial resolution. Understanding the specific signaling pathways involved in these actions of dopamine and their hierarchical organization may facilitate the drug discovery process that could lead to the design of new therapeutic approaches to clear lung edema in patients with acute lung injury and to decrease fluid overload during congestive heart failure and hypertension.
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Affiliation(s)
- Alejandro M Bertorello
- Department of Medicine, Atherosclerosis Research Unit, Membrane Signaling Networks, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
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27
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Muscella A, Storelli C, Marsigliante S. Atypical PKC-zeta and PKC-iota mediate opposing effects on MCF-7 Na+/K+ATPase activity. J Cell Physiol 2005; 205:278-85. [PMID: 15887250 DOI: 10.1002/jcp.20396] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We demonstrated previously that in serum-starved MCF-7 breast cancer cell line, Ang II increased Na+/K+ATPase activity and activated the protein kinase C zeta (PKC-zeta) (Muscella et al., 2002 J Endocrinol 173:315-323; 2003 J Cell Physiol 197:61-68.). The aim of the present study was to investigate the modulation of the activity of the Na+/K+ATPase by PKC-zeta in MCF-7 cells. Here, using serum-starved MCF-7 cells, we have demonstrated that the effect of Ang II on the Na+/K+ATPase activity was inhibited by a synthetic myristoylated peptide with sequences based on the endogenous PKC-zeta pseudosubstrate region (zeta-PS) and by high doses of GF109203X, inhibitor of PKCs. When MCF-7 cells, grown in 10% fetal bovine serum (FBS), were stimulated with Ang II a dose- and time-dependent inhibition of the Na+/K+ATPase activity was obtained. Under this growth condition we found that mRNAs for AT1, AT2, and for Na+/K+ATPase alpha1 and alpha3 subunits were unchanged; besides both the activity of the Na+/K+ATPase and the level of PKC-zeta also were unaffected by the serum. The atypical PKC-iota level (present in very low abundance in serum-starved MCF-7) was increased and Ang II provoked its translocation from the cytosol to plasma membrane. PKC-zeta was localized to the membrane, and upon Ang II treatment its cellular localization did not change. The Ang II-mediated decrease of the Na+/K+ATPase activity was inhibited by high doses of GF109203X but not by zeta-PS, thus indicating that such effect was not due to PKC-zeta activity. The treatment of cells with PKC-iota antisense oligodeoxynucleotides inhibited the effects of Ang II on the Na+/K+ATPase activity. Additionally, the effect of Ang II on Na+/K+ATPase activity was also blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin and LY294002, and by the actin depolymerizing agents, cytochalasin D. In conclusion, in MCF-7 cells Ang II modulates the Na+/K+ATPase activity by both atypical PKC-zeta/-iota. The effects of Ang II are opposite depending upon the presence of the serum-sensitive PKC-iota, with the inhibitory effect possibly due to the redistribution of sodium pump from plasma membrane to the inactive intracellular pool.
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Affiliation(s)
- Antonella Muscella
- Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Universitá degli Studi di Lecce, Ecotekne, Via Provinciale per Monteroni, Lecce, Italy
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Wu ZQ, Li M, Chen J, Chi ZQ, Liu JG. Involvement of cAMP/cAMP-dependent protein kinase signaling pathway in regulation of Na+,K+-ATPase upon activation of opioid receptors by morphine. Mol Pharmacol 2005; 69:866-76. [PMID: 16317112 DOI: 10.1124/mol.105.016501] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The depolarization of neurons induced by impairment of Na+,K+-ATPase activity after long-term opiate treatment has been shown to involve the development of opioid dependence. However, the mechanisms underlying changes in Na+,K+-ATPase activity after opioid treatment are unclear. The best-established molecular adaptation to long-term opioid exposure is up-regulation of the cAMP/cAMP-dependent protein kinase (PKA) signaling pathway; this study, therefore, was undertaken to investigate the role of up-regulation of cAMP/PKA signaling pathway in alteration of the mouse hippocampal Na+,K+-ATPase activity. The results demonstrated that short-term morphine treatment dose dependently stimulated Na+,K+-ATPase activity. This action could be significantly suppressed by adenylyl cyclase activator 7beta-acetoxy-8,13-epoxy-1alpha,6beta,9alpha-trihydroxylabd-14-en-11-one (forskolin), or the cAMP analog dibutyryl-cAMP. Contrary to short-term morphine treatment, long-term treatment significantly inhibited Na+,K+-ATPase activity. Moreover, an additional decrease in Na+,K+-ATPase activity was observed by naloxone precipitation. The effects of both short- and long-term morphine treatment on Na+,K+-ATPase activity were naltrexone-reversible. The regulation of Na+,K+-ATPase activity by morphine was inversely correlated with intracellular cAMP accumulation. N-[2-(4-Bromocinnamylamino)ethyl]-5-isoquinoline (H89), a specific PKA inhibitor, mimicked the stimulatory effect of short-term morphine but antagonized the inhibitory effect of long-term morphine treatment on Na+,K+-ATPase activity. However, okadaic acid, a protein phosphatase inhibitor, suppressed short-term morphine stimulation but potentiated long-term morphine inhibition of Na+,K+-ATPase activity. The regulation of Na+,K+-ATPase activity by morphine treatment seemed to associate with the alteration in phosphorylation level but not to be relevant to the change in abundance of Na+,K+-ATPase. These findings strongly demonstrate that cAMP/PKA signaling pathway involves regulation of Na+,K+-ATPase activity after activation of opioid receptors.
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Affiliation(s)
- Zhao-Qiu Wu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, No.555 Zuchongzhi Rd., Shanghai 201203, China
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Zeng C, Sanada H, Watanabe H, Eisner GM, Felder RA, Jose PA. Functional genomics of the dopaminergic system in hypertension. Physiol Genomics 2005; 19:233-46. [PMID: 15548830 DOI: 10.1152/physiolgenomics.00127.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. Under normal conditions, D(1)-like receptors (D(1) and D(5)) inhibit sodium transport in the kidney and intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats (SHRs) and in humans with essential hypertension, the D(1)-like receptor-mediated inhibition of epithelial sodium transport is impaired because of an uncoupling of the D(1)-like receptor from its G protein/effector complex. The uncoupling is receptor specific, organ selective, nephron-segment specific, precedes the onset of hypertension, and cosegregates with the hypertensive phenotype. The defective transduction of the renal dopaminergic signal is caused by activating variants of G protein-coupled receptor kinase type 4 (GRK4: R65L, A142V, A486V). The GRK4 locus is linked to and GRK4 gene variants are associated with human essential hypertension, especially in salt-sensitive hypertensive subjects. Indeed, the presence of three or more GRK4 variants impairs the natriuretic response to dopaminergic stimulation in humans. In genetically hypertensive rats, renal inhibition of GRK4 expression ameliorates the hypertension. In mice, overexpression of GRK4 variants causes hypertension either with or without salt sensitivity according to the variant. GRK4 gene variants, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic factors (e.g., angiotensin II type 1 receptor) to predominate, may be responsible for salt sensitivity. Subclasses of hypertension may occur because of additional perturbations caused by variants of other genes, the quantitative interaction of which may vary depending upon the genetic background.
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Affiliation(s)
- Chunyu Zeng
- Department of Cardiology, Daping Hospital, Third Military Medical University, Chongqing, People's Republic of China
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Periyasamy SM, Liu J, Tanta F, Kabak B, Wakefield B, Malhotra D, Kennedy DJ, Nadoor A, Fedorova OV, Gunning W, Xie Z, Bagrov AY, Shapiro JI. Salt loading induces redistribution of the plasmalemmal Na/K-ATPase in proximal tubule cells. Kidney Int 2005; 67:1868-77. [PMID: 15840034 DOI: 10.1111/j.1523-1755.2005.00285.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND We have reported that digitalis-like substances (cardiotonic steroids), including marinobufagenin (MBG), induce endocytosis of the plasmalemmal Na/K-ATPase in LLC-PK1 cells. The current report addresses the potential relevance of plasmalemmal Na/K-ATPase redistribution to in vivo salt handling. METHODS Male Sprague-Dawley rats were given 1 week of a high salt (4.0% NaCl) or normal salt (0.4% NaCl) diet. Urinary sodium excretion, as well as MBG excretion, was monitored, and proximal tubules were isolated using a Percoll gradient method. Tubular (86)Rb uptake, Na/K-ATPase enzymatic activity, and Na/K-ATPase alpha1 subunit density were determined. RESULTS The high salt diet increased urinary sodium (17.8 +/- 1.8 vs. 2.5 +/- 0.3 mEq/day, P < 0.01) and MBG excretion (104 +/- 12 vs. 26 +/- 4 pmol/day), and decreased proximal tubular (86)Rb uptake (0.44 +/- 0.07 vs. 1.00 +/- 0.10, P < 0.01) and Na/K-ATPase enzymatic activity (5.1 +/- 1.1 vs. 9.9 +/- 1.6 micromol/mg pr/hr, P < 0.01) relative to the normal diet. Proximal tubular Na/K-ATPase alpha1 protein density was decreased in the plasmalemma fraction but increased in both early and late endosomes following the high salt diet. In rats fed a high salt diet, anti-MBG antibody caused a 60% reduction in urinary sodium excretion, substantial increases in proximal tubule (86)Rb uptake, and Na/K-ATPase enzymatic activity, as well as significant decreases in the early and late endosomal Na/K-ATPase alpha1 protein content. CONCLUSION These data suggest that redistribution of the proximal tubule Na/K-ATPase in response to endogenous cardiotonic steroids plays an important role in renal adaptation to salt loading.
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31
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Li F, Malik KU. Angiotensin II-induced Akt activation is mediated by metabolites of arachidonic acid generated by CaMKII-stimulated Ca2+-dependent phospholipase A2. Am J Physiol Heart Circ Physiol 2005; 288:H2306-16. [PMID: 15637121 DOI: 10.1152/ajpheart.00571.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Angiotensin II (ANG II) promotes vascular smooth muscle cell (VSMC) growth, stimulates Ca2+-calmodulin (CaM)-dependent kinase II (CaMKII), and activates cytosolic Ca2+-dependent phospholipase A2(cPLA2), which releases arachidonic acid (AA). ANG II also generates H2O2and activates Akt, which have been implicated in ANG II actions in VSMC. This study was conducted to investigate the relationship of these signaling molecules to Akt activation in rat aortic VSMC. ANG II increased Akt activity, as measured by its phosphorylation at serine-473. ANG II (200 nM)-induced Akt phosphorylation was decreased by extracellular Ca2+depletion and calcium chelator EGTA and inhibitors of CaM [ N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide] and CaMKII {(2-[ N-(2-hydroxyethyl)]- N-(4-me-thoxybenzenesulfonyl)]amino- N-(4-chlorocinnamyl)- N-methylbenzyl-amine)}. cPLA2inhibitor pyrrolidine-1, antisense oligonucleotide, and retroviral small interfering RNA also attenuated ANG II-induced Akt phosphorylation. AA increased Akt phosphorylation, and AA metabolism inhibitor 5,8,11,14-eicosatetraynoic acid (ETYA) blocked ANG II- and AA-induced Akt phosphorylation (199.03 ± 27.91% with ANG II and 110.18 ± 22.40% with ETYA + ANG II; 405.00 ± 86.22% with AA and 153.97 ± 63.26% with ETYA + AA). Inhibitors of lipoxygenase (cinnamyl-3,4-dihydroxy-α-cyanocinnamate) and cytochrome P-450 (ketoconazole and 17-octadecynoic acid), but not cyclooxygenase (indomethacin), attenuated ANG II- and AA-induced Akt phosphorylation. Furthermore, 5( S)-, 12( S)-, 15( S)-, and 20-hydroxyeicosatetraenoic acids and 5,6-, 11,12-, and 14,15-epoxyeicosatrienoic acids increased Akt phosphorylation. Catalase inhibited ANG II-increased H2O2production but not Akt phosphorylation. Oleic acid, which also increased H2O2production, did not cause Akt phosphorylation. These data suggest that ANG II-induced Akt activation in VSMC is mediated by AA metabolites, most likely generated via lipoxygenase and cytochrome P-450 consequent to AA released by CaMKII-activated cPLA2and independent of H2O2production.
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Affiliation(s)
- Fang Li
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Efendiev R, Chen Z, Krmar RT, Uhles S, Katz AI, Pedemonte CH, Bertorello AM. The 14-3-3 protein translates the NA+,K+-ATPase {alpha}1-subunit phosphorylation signal into binding and activation of phosphoinositide 3-kinase during endocytosis. J Biol Chem 2005; 280:16272-7. [PMID: 15722354 DOI: 10.1074/jbc.m500486200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Clathrin-dependent endocytosis of Na(+),K(+)-ATPase molecules in response to G protein-coupled receptor signals is triggered by phosphorylation of the alpha-subunit and the binding of phosphoinositide 3-kinase. In this study, we describe a molecular mechanism linking phosphorylation of Na(+),K(+)-ATPase alpha-subunit to binding and activation of phosphoinositide 3-kinase. Co-immunoprecipitation studies, as well as experiments using confocal microscopy, revealed that dopamine favored the association of 14-3-3 protein with the basolateral plasma membrane and its co-localization with the Na(+),K(+)-ATPase alpha-subunit. The functional relevance of this interaction was established in opossum kidney cells expressing a 14-3-3 dominant negative mutant, where dopamine failed to decrease Na(+),K(+)-ATPase activity and to promote its endocytosis. The phosphorylated Ser-18 residue within the alpha-subunit N terminus is critical for 14-3-3 binding. Activation of phosphoinositide 3-kinase by dopamine during Na(+),K(+)-ATPase endocytosis requires the binding of the kinase to a proline-rich domain within the alpha-subunit, and this effect was blocked by the presence of a 14-3-3 dominant negative mutant. Thus, the 14-3-3 protein represents a critical linking mechanism for recruiting phosphoinositide 3-kinase to the site of Na(+),K(+)-ATPase endocytosis.
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Affiliation(s)
- Riad Efendiev
- Department of Medicine, Atherosclerosis Research Unit, Membrane Signaling Networks, Karolinska Institutet, Karolinska University Hospital-Solna, S-171 76 Stockholm, Sweden
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Liu J, Kesiry R, Periyasamy SM, Malhotra D, Xie Z, Shapiro JI. Ouabain induces endocytosis of plasmalemmal Na/K-ATPase in LLC-PK1 cells by a clathrin-dependent mechanism. Kidney Int 2005; 66:227-41. [PMID: 15200429 DOI: 10.1111/j.1523-1755.2004.00723.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND We have demonstrated that ouabain causes dose- and time-dependent decreases in (86)Rb uptake in porcine proximal tubular (LLC-PK1) cells. The present study addresses the molecular mechanisms involved in this process. METHODS Studies were performed with cultured LLC-PK1 and Src family kinase deficient (SYF) cells. RESULTS We found that 50 nmol/L ouabain applied to the basal, but not apical, aspect for 12 hours caused decreases in the plasmalemmal Na/K-ATPase. This loss of plasmalemmal Na/K-ATPase reverses completely within 12 to 24 hours after removal of ouabain. Ouabain also increased the Na/K-ATPase content in both early and late endosomes, activated phosphatidylinositol 3-kinase (PI(3)K), and also caused a translocation of some Na/K-ATPase to the nucleus. Immunofluorescence demonstrated that the Na/K-ATPase colocalized with clathrin both before and after exposure to ouabain, and immunoprecipitation experiments confirmed that ouabain stimulated interactions among the Na/K-ATPase, adaptor protein-2 (AP-2), and clathrin. Potassium (K) depletion, chlorpromazine, or PI(3)K inhibition all significantly attenuated this ouabain-induced endocytosis. Inhibition of the ouabain-activated signaling process through Src by 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) significantly attenuated ouabain-induced endocytosis. Moreover, experiments performed in SYF cells demonstrated that ouabain induced increases in the endocytosis of the Na/K-ATPase when Src was reconstituted (SYF+), but not in the Src-deficient (SYF-) cells. CONCLUSION These data demonstrate that ouabain stimulates a clathrin-dependent endocytosis pathway that translocates the Na/K-ATPase to intracellular compartments, thus suggesting a potential role of endocytosis in ouabain-induced signal transduction as well as proximal tubule sodium handling.
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Affiliation(s)
- Jiang Liu
- The Department of Medicine, Medical College of Ohio, Toledo, Ohio, USA
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Efendiev R, Krmar RT, Ogimoto G, Zwiller J, Tripodi G, Katz AI, Bianchi G, Pedemonte CH, Bertorello AM. Hypertension-linked mutation in the adducin alpha-subunit leads to higher AP2-mu2 phosphorylation and impaired Na+,K+-ATPase trafficking in response to GPCR signals and intracellular sodium. Circ Res 2004; 95:1100-8. [PMID: 15528469 DOI: 10.1161/01.res.0000149570.20845.89] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Alpha-adducin polymorphism in humans is associated with abnormal renal sodium handling and high blood pressure. The mechanisms by which mutations in adducin affect the renal set point for sodium excretion are not known. Decreases in Na+,K+-ATPase activity attributable to endocytosis of active units in renal tubule cells by dopamine regulates sodium excretion during high-salt diet. Milan rats carrying the hypertensive adducin phenotype have a higher renal tubule Na+,K+-ATPase activity, and their Na+,K+-ATPase molecules do not undergo endocytosis in response to dopamine as do those of the normotensive strain. Dopamine fails to promote the interaction between adaptins and the Na+,K+-ATPase because of adaptin-mu2 subunit hyperphosphorylation. Expression of the hypertensive rat or human variant of adducin into normal renal epithelial cells recreates the hypertensive phenotype with higher Na+,K+-ATPase activity, mu2-subunit hyperphosphorylation, and impaired Na+,K+-ATPase endocytosis. Thus, increased renal Na+,K+-ATPase activity and altered sodium reabsorption in certain forms of hypertension could be attributed to a mutant form of adducin that impairs the dynamic regulation of renal Na+,K+-ATPase endocytosis in response to natriuretic signals.
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Affiliation(s)
- Riad Efendiev
- Department of Medicine, Atherosclerosis Research Unit, Membrane Signaling Networks, Karolinska Institutet, Karolinska University Hospital, S-171 76 Stockholm, Sweden
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35
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Lei J, Mariash CN, Ingbar DH. 3,3′,5-Triiodo-l-thyronine Up-regulation of Na,K-ATPase Activity and Cell Surface Expression in Alveolar Epithelial Cells Is Src Kinase- and Phosphoinositide 3-Kinase-dependent. J Biol Chem 2004; 279:47589-600. [PMID: 15342623 DOI: 10.1074/jbc.m405497200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We previously reported that thyroid hormone, 3,3',5-triiodo-l-thyronine (T3), increased Na,K-ATPase activity of adult rat alveolar epithelial cells in a transcription-independent manner via increased cell surface expression of the alpha(1) and beta(1) subunits of Na,K-ATPase. Now we sought to identify signaling molecules necessary for T3 stimulation of Na,K-ATPase activity in alveolar epithelial cells. Whereas protein kinase A inhibitor H-8 and protein kinase C inhibitor bisindolymaleimide did not block the T3-induced increase in Na,K-ATPase activity, two inhibitors of phosphoinositide 3-kinase (PI3K), wortmannin and Ly294002, and two Src kinase inhibitors, PP1 and PP2, blocked the T3-induced Na,K-ATPase activity. T3 stimulated the activity of PI3K as measured by phosphatidylinositol 3-phosphate. T3 also stimulated the serine 473 phosphorylation of the PI3K downstream molecule PKB/Akt in a dose-dependent manner. Transient expression of a constitutively active mutant of the PI3K catalytic subunit p110 augmented Na,K-ATPase activity and increased the amount of cell surface Na,K-ATPase alpha(1) subunit protein. T3 also stimulated Src family kinase activity. Transient expression of a constitutively active Src kinase increased Na,K-ATPase activity, PI3K activity, and phosphorylation of PKB/Akt at serine 473. PP1 or PP2 blocked T3-stimulated PKB/Akt phosphorylation at serine 473 and PI3K activity that was activated by an active mutant of Src; however, wortmannin did not inhibit the T3-stimulated Src kinase activity. Although PP1 and wortmannin abolished the increase in Na,K-ATPase activity induced by the active mutant of Src, PP1 did not inhibit the active mutant of PI3K-up-regulated Na,K-ATPase activity. In summary, T3 stimulates the PI3K/PKB pathway via the Src family of tyrosine kinases, and activation of both the Src family kinases and PI3K is required for the T3-induced stimulation of Na,K-ATPase activity and its cell surface expression in adult rat alveolar epithelial cells.
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Affiliation(s)
- Jianxun Lei
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA
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36
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Blondeau F, Ritter B, Allaire PD, Wasiak S, Girard M, Hussain NK, Angers A, Legendre-Guillemin V, Roy L, Boismenu D, Kearney RE, Bell AW, Bergeron JJM, McPherson PS. Tandem MS analysis of brain clathrin-coated vesicles reveals their critical involvement in synaptic vesicle recycling. Proc Natl Acad Sci U S A 2004; 101:3833-8. [PMID: 15007177 PMCID: PMC374330 DOI: 10.1073/pnas.0308186101] [Citation(s) in RCA: 255] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tandem MS has identified 209 proteins of clathrin-coated vesicles (CCVs) isolated from rat brain. An overwhelming abundance of peptides were assigned to the clathrin coat with a 1:1 stoichiometry observed for clathrin heavy and light chains and a 2:1 stoichiometry of clathrin heavy chain with clathrin adaptor protein heterotetramers. Thirty-two proteins representing many of the known components of synaptic vesicles (SVs) were identified, supporting that a main function for brain CCVs is to recapture SVs after exocytosis. A ratio of vesicle-N-ethylmaleimide-sensitive factor attachment protein receptors to target-N-ethylmaleimide-sensitive factor attachment protein receptors, similar to that previously detected on SVs, supports a single-step model for SV sorting during CCV-mediated recycling of SVs. The uncovering of eight previously undescribed proteins, four of which have to date been linked to clathrin-mediated trafficking, further attests to the value of the current organelle-based proteomics strategy.
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Affiliation(s)
- Francois Blondeau
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC, Canada H3A 2B4
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37
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Abstract
In order to carry out their physiological functions, ion transport proteins must be targeted to the appropriate domains of cell membranes. Regulation of ion transport activity frequently involves the tightly controlled delivery of intracellular populations of transport proteins to the plasma membrane or the endocytic retrieval of transport proteins from the cell surface. Transport proteins carry signals embedded within their structures that specify their subcellular distributions and endow them with the capacity to participate in regulated membrane trafficking processes. Recently, a great deal has been learned about the biochemical nature of these signals, as well as about the cellular machinery that interprets them and acts upon their messages.
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Affiliation(s)
- Theodore R Muth
- Department of Biology, CUNY Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11231, USA.
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38
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Carattino MD, Hill WG, Kleyman TR. Arachidonic acid regulates surface expression of epithelial sodium channels. J Biol Chem 2003; 278:36202-13. [PMID: 12837767 DOI: 10.1074/jbc.m300312200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epithelial Na+ channels (ENaCs) are regulated by the phospholipase A2 (PLA2) product arachidonic acid. Pharmacological inhibition of PLA2 with aristolochic acid induced a significant increase in amiloride-sensitive currents in Xenopus oocytes expressing ENaC. Arachidonic acid or 5,8,11,14-eicosatetraynoic acid (ETYA), a non-metabolized analog of arachidonic acid, induced a time-dependent inhibition of Na+ transport. These effects were also observed by co-expression of a calcium-independent or a calcium-dependent PLA2. Channels with a truncated alpha, beta,or gamma C terminus were not inhibited by arachidonic acid or ETYA. Furthermore, mutation of Tyr618 in the PY motif of the beta subunit abrogated the inhibitory effect of ETYA, suggesting that intact PY motifs participate in arachidonic acid-mediated ENaC inhibition. Analyses of channels expressing a series of beta subunit C-terminal truncations revealed a second region N-terminal to the PY motif (spanning residues betaVal580-betaGly599) that allowed for ETYA-mediated ENaC inhibition. Analyses of both ENaC surface expression and ENaC trafficking with mutants that either gate channels open or closed in response to [(2-(trimethylammonium) ethyl] methanethiosulfonate bromide, or with brefeldin A, suggest that ETYA reduces channel surface expression by inhibiting ENaC exocytosis and increasing ENaC endocytosis.
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Affiliation(s)
- Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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39
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Teixeira VL, Katz AI, Pedemonte CH, Bertorello AM. Isoform-specific regulation of Na+,K+-ATPase endocytosis and recruitment to the plasma membrane. Ann N Y Acad Sci 2003; 986:587-94. [PMID: 12763893 DOI: 10.1111/j.1749-6632.2003.tb07257.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Na(+),K(+)-ATPase traffics between the plasma membrane and intracellular compartments in response to acute changes in membrane receptor activation. These effects are accomplished by a time-dependent interaction of the Na(+),K(+)-ATPase alpha-subunit with specific intracellular signaling molecules either at the plasma membrane (endocytosis) or at the endosome's membranes (recruitment). Most of these studies have been performed in rat renal epithelial cells in which only the alpha(1) isoenzyme is present. Studies in neurons from the neostriatum in which all three alpha-subunit isoforms are present indicate that neurotransmitter-dependent regulation of Na(+),K(+)-ATPase activity displays isoform specificity and also suggest a more complex organization of the intracellular signaling networks controlling Na(+),K(+)-ATPase traffic in mammalian cells.
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Affiliation(s)
- Vera Lucas Teixeira
- Department of Medicine, Atherosclerosis Research Unit, Karolinska Institutet, Karolinska Hospital, 171 76 Stockholm, Sweden
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40
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Pagel P, Zatti A, Kimura T, Duffield A, Chauvet V, Rajendran V, Caplan MJ. Ion pump-interacting proteins: promising new partners. Ann N Y Acad Sci 2003; 986:360-8. [PMID: 12763851 DOI: 10.1111/j.1749-6632.2003.tb07215.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The sorting and regulation of the Na,K and H,K-ATPases requires that the pump proteins must associate, at least transiently, with kinases, phosphatases, scaffolding molecules, and components of the cellular trafficking machinery. The identities of these interacting proteins and the nature of their associations with the pump polypeptides have yet to be elucidated. We have begun a series of yeast two-hybrid screens employing structurally defined segments of pump polypeptides as baits in order to gain insight into the nature and function of these interacting proteins.
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Affiliation(s)
- Philipp Pagel
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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41
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Kristensen B, Birkelund S, Jorgensen PL. Expression of a Na,K-ATPase-EGFP chimera in COS cells: can internalization explain PKA- or PKC-mediated inhibition of 86Rb uptake? Ann N Y Acad Sci 2003; 986:546-7. [PMID: 12763885 DOI: 10.1111/j.1749-6632.2003.tb07249.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Bo Kristensen
- Biomembrane Center, The August Krogh Institute, University of Copenhagen, Universitetsparken 13, Denmark
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42
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Marsigliante S, Muscella A, Elia MG, Greco S, Storelli C. Angiotensin II AT1 receptor stimulates Na+ -K+ATPase activity through a pathway involving PKC-zeta in rat thyroid cells. J Physiol 2003; 546:461-70. [PMID: 12527732 PMCID: PMC2342509 DOI: 10.1113/jphysiol.2002.027466] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Angiotensin II (Ang II) receptor subtype 1, AT1, is expressed by the rat thyroid. A relationship between thyroid function and several components of the renin-angiotensin system has also been established, but the Ang II cellular effects in thyrocytes and its transduction signalling remain undefined. The aim of the present paper was to investigate the modulation of the activity of the Na(+)-K(+)ATPase by Ang II and its intracellular transduction pathway in PC-Cl3 cells, an established epithelial cell line derived from rat thyroid. Here we have demonstrated, by RT-PCR analysis, the expression of mRNA for the Ang II AT1 receptor in PC-Cl3 cells; mRNA for the Ang II AT2 receptor was not detected. Ang II was not able to affect the intracellular Ca(2+) concentration in fura-2-loaded cells, but it stimulated the translocation from the cytosol to the plasma membrane of atypical protein kinase C-zeta (PKC-zeta) and -iota (PKC-) isoforms with subsequent phosphorylation of the extracellular signal-regulated kinases 1 and 2 (ERK1 and 2). Translocated atypical PKCs displayed temporally different activations, the activation of PKC-zeta being the fastest. PC-Cl3 cells stimulated with increasing Ang II concentrations showed dose- and time-dependent activation of the Na(+)-K(+)ATPase activity, which paralleled the PKC-zeta translocation time course. Na(+)-K(+)ATPase activity modulation was dependent on PKC activation since the PKC antagonist staurosporine abolished the stimulatory effect of Ang II. The inhibition of the ERK kinases 1 and 2 (MEK1 and 2) by PD098059 (2'-amino-3'-methoxyflavone) failed to block the effect of Ang II on the Na(+)-K(+)ATPase activity. In conclusion, our results suggest that Ang II modulates Na(+)-K(+)ATPase activity in PC-Cl3 cells through the AT1 receptor via activation of atypical PKC-zeta while the Ang II-activated PKC- appears to have other as yet unknown functions.
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Affiliation(s)
- S Marsigliante
- Laboratorio di Fisiologia, Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università di Lecce, Ecotekne, Via Prov. le per Monteroni, 73100 Lecce, Italy.
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Muscella A, Elia MG, Greco S, Storelli C, Marsigliante S. Activation of P2Y2 purinoceptor inhibits the activity of the Na+/K+-ATPase in HeLa cells. Cell Signal 2003; 15:115-21. [PMID: 12401526 DOI: 10.1016/s0898-6568(02)00062-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The role of ATP on regulation of the Na(+)/K(+)-ATPase activity in the human cancerous HeLa cells was investigated. HeLa cells stimulated with increasing ATP concentrations showed a dose-dependent inhibition of the Na(+)/K(+)-ATPase activity. These effects were also obtained by UTP. ATP and UTP provoked a rise in intracellular calcium concentration ([Ca(2+)](i)) persisting for at least 4 min. The inhibitor of phospholipase C, U73122, blocked the elevation of [Ca(2+)](i) provoked by ATP/UTP. The expression of mRNA for P2Y2 and P2Y6 receptors was demonstrated by RT-PCR. ATP/UTP activated PKC-alpha, -betaI and -epsilon isoforms, but not PKC-delta and -zeta. The inhibition of the Na(+)/K(+)-ATPase activity by ATP/UTP was blocked by Gö6976, a specific inhibitor of the calcium-dependent PKCs. In conclusion, our results suggest that ATP/UTP modulate Na(+)/K(+)-ATPase activity in HeLa cells through the P2Y2 purinoceptor via calcium mobilisation and activation of calcium-dependent PKCs.
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Affiliation(s)
- Antonella Muscella
- Department of Biological Sciences and Environmental Technology (DisTeBA), Laboratory of Cell Physiology, University of Lecce, Ecotekne, Via Provinciale per Monteroni, 73100 Lecce, Italy
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Liu J, Periyasamy SM, Gunning W, Fedorova OV, Bagrov AY, Malhotra D, Xie Z, Shapiro JI. Effects of cardiac glycosides on sodium pump expression and function in LLC-PK1 and MDCK cells. Kidney Int 2002; 62:2118-25. [PMID: 12427136 DOI: 10.1046/j.1523-1755.2002.00672.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The decreases in proximal tubule sodium reabsorption seen with chronic renal failure and volume expansion have been ascribed to circulating digitalis-like substances (DLS). However, the circulating concentrations of DLS do not acutely inhibit the sodium pump to a degree consistent with the observed changes in proximal tubule sodium reabsorption. METHODS We examined how cell lines that simulated proximal (LLC-PK1) and distal tubule (MDCK) cells responded to acute (30 min) and long-term (up to 12 hours) Na+,K+-ATPase inhibition with DLS. RESULTS In LLC-PK1, but not MDCK cells, low concentrations of ouabain decreased 86Rb uptake profoundly in a time and dose dependent manner. In LLC-PK1 cells grown to confluence, transcellular 22Na flux was markedly reduced in concert with the decreases in 86Rb uptake. Similar findings were observed with marinobufagenin (MBG) and deproteinated extract of serum derived from patients with chronic renal failure. However, inhibition of the Na+,K+-ATPase with low extracellular potassium concentrations did not produce any of these effects. Western and Northern blots detected no change in alpha1 Na+,K+-ATPase protein and message RNA, respectively, in LLC-PK1 cells treated with ouabain for 12 hours. However, the decrease in enzymatic activity of Na+,K+-ATPase of these cells was comparable to observed decreases in 86Rb uptake. Differential centrifugation as well as biotinylation experiments demonstrated a shift of the Na+,K+-ATPase from the plasmalemma with prolonged ouabain treatment. CONCLUSIONS The results show that binding of cardiac glycosides by proximal (but not distal) tubular cells results in internalization of Na+,K+-ATPase with the net effect to amplify inhibition of the Na+,K+-ATPase. As the circulating concentrations of DLS increase with chronic renal failure and volume expansion, we suggest that this phenomenon explains some of the decreased sodium reabsorption by the proximal tubule seen in these conditions.
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Affiliation(s)
- Jiang Liu
- Department of Medicine, Medical College of Ohio, Toledo, Ohio 43614, USA
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45
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Efendiev R, Yudowski GA, Zwiller J, Leibiger B, Katz AI, Berggren PO, Pedemonte CH, Leibiger IB, Bertorello AM. Relevance of dopamine signals anchoring dynamin-2 to the plasma membrane during Na+,K+-ATPase endocytosis. J Biol Chem 2002; 277:44108-14. [PMID: 12205083 DOI: 10.1074/jbc.m205173200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Clathrin-dependent endocytosis of Na(+),K(+)-ATPase in response to dopamine regulates its catalytic activity in intact cells. Because fission of clathrin-coated pits requires dynamin, we examined the mechanisms by which dopamine receptor signals promote dynamin-2 recruitment and assembly at the site of Na(+),K(+)-ATPase endocytosis. Western blotting revealed that dopamine increased the association of dynamin-2 with the plasma membrane and with phosphatidylinositol 3-kinase. Dopamine inhibited Na(+),K(+)-ATPase activity in OK cells and in those overexpressing wild type dynamin-2 but not in cells expressing a dominant-negative mutant. Dephosphorylation of dynamin is important for its assembly. Dopamine increased protein phosphatase 2A activity and dephosphorylated dynamin-2. In cells expressing a dominant-negative mutant of protein phosphatase 2A, dopamine failed to dephosphorylate dynamin-2 and to reduce Na(+),K(+)-ATPase activity. Dynamin-2 is phosphorylated at Ser(848), and expression of the S848A mutant significantly blocked the inhibitory effect of dopamine. These results demonstrate a distinct signaling network originating from the dopamine receptor that regulates the state of dynamin-2 phosphorylation and that promotes its location (by interaction with phosphatidylinositol 3-kinase) at the site of Na(+),K(+)-ATPase endocytosis.
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Affiliation(s)
- Riad Efendiev
- Department of Molecular Medicine, The Rolf Luft Center for Diabetes Research, Karolinska Institutet, Karolinska Hospital, S-171 76 Stockholm, Sweden
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46
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Véga C, Pellerin L, Dantzer R, Magistretti PJ. Long-term modulation of glucose utilization by IL-1 alpha and TNF-alpha in astrocytes: Na+ pump activity as a potential target via distinct signaling mechanisms. Glia 2002; 39:10-8. [PMID: 12112371 DOI: 10.1002/glia.10080] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) markedly stimulate glucose utilization in primary cultures of mouse cortical astrocytes. The mechanism that gives rise to this effect, which takes place several hours after application of cytokine, has remained unclear. Experiments were conducted to identify the major signaling cascades involved in the metabolic action of cytokine. First, the selective IL-1 receptor antagonist (IL-1ra) prevents the effect of IL-1alpha on glucose utilization in a concentration-dependent manner, whereas it has no effect on the action of TNF-alpha. Then, using inhibitors of three classical signaling cascades known to be activated by cytokines, it appears that the PI3 kinase is essential for the effect of both IL-1alpha and TNF-alpha, whereas the action of IL-1alpha also requires activation of the MAP kinase pathway. Participation of a phospholipase C-dependent pathway does not appear critical for both IL-1alpha and TNF-alpha. Inhibition of NO synthase by L-NAME did not prevent the metabolic response to both IL-1alpha and TNF-alpha, indicating that nitric oxide is probably not involved. In contrast, the Na(+)/K(+) ATPase inhibitor ouabain prevents the IL-1alpha- and TNF-alpha-stimulated 2-deoxyglucose (2DG) uptake. When treatment of astrocytes with a cytokine was followed 24 h later by an acute application of glutamate, a synergistic enhancement in glucose utilization was observed. This effect was greatly reduced by ouabain. These data suggest that Na(+) pump activity is a common target for both the long-term metabolic action of cytokines promoted by the activation of distinct signaling pathways and the enhanced metabolic response to glutamate.
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Affiliation(s)
- Céline Véga
- Institut de Physiologie, Lausanne, Switzerland
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47
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Gomes P, Soares-da-Silva P. Role of cAMP-PKA-PLC signaling cascade on dopamine-induced PKC-mediated inhibition of renal Na(+)-K(+)-ATPase activity. Am J Physiol Renal Physiol 2002; 282:F1084-96. [PMID: 11997325 DOI: 10.1152/ajprenal.00318.2001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We studied the molecular events set into motion by stimulation of D(1)-like receptors downstream of Na(+)-K(+)-ATPase, while measuring apical-to-basal ouabain-sensitive, amphotericin B-induced increases in short-circuit current in opossum kidney (OK) cells. The D(1)-like receptor agonist SKF-38393 decreased Na(+)-K(+)-ATPase activity (IC(50), 130 nM). This effect was prevented by the D(1)-like receptor antagonist SKF-83566, overnight cholera toxin treatment, the protein kinase A (PKA) antagonist H-89, or the PKC antagonist chelerythrine, but not the mitogen-activated PK inhibitor PD-098059 or phosphatidylinositol 3-kinase inhibitors wortmannin and LY-294002. Dibutyryl cAMP (DBcAMP) and phorbol 12,13-dibutyrate (PDBu) both effectively reduced Na(+)-K(+)-ATPase activity. PKA downregulation abolished the inhibitory effects of SKF-38393 and DBcAMP but not those of PDBu. PKC downregulation abolished inhibition by PDBu, SKF-38393, and DBcAMP. The phospholipase C (PLC) inhibitor U-73122 prevented inhibition by SKF-38393 and DBcAMP. However, DBcAMP increased PLC activity. Although OK cells express both G(s)alpha and G(q/11)alpha proteins, D(1)-like receptors are coupled to G(s)alpha proteins only, as evidenced by studies in cells treated overnight with specific antibodies raised against G(s)alpha and G(q/11)alpha proteins. We conclude that PLC and Na(+)-K(+)-ATPase are effector proteins for PKA and PKC, respectively, after stimulation of D(1)-like receptors coupled to G(s)alpha proteins, in a sequence of events that begins with adenylyl cyclase-PKA system activation followed by PLC-PKC system activation.
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Affiliation(s)
- Pedro Gomes
- Institute of Pharmacology and Therapeutics, Faculty of Medicine, 4200 Porto, Portugal
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Gomes P, Soares-da-Silva P. Dopamine-induced inhibition of Na+-K+-ATPase activity requires integrity of actin cytoskeleton in opossum kidney cells. ACTA PHYSIOLOGICA SCANDINAVICA 2002; 175:93-101. [PMID: 12028129 DOI: 10.1046/j.1365-201x.2002.00972.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study evaluated the importance of the association between Na+-K+-ATPase and the actin cytoskeleton on dopamine-induced inhibition of Na+-K+-ATPase activity. The approach used measures the transepithelial transport of Na+ in monolayers of opossum kidney (OK) cells, when the Na+ delivered to Na+-K+-ATPase was increased at the saturating level by amphotericin B. The maximal amphotericin B (1.0 microg mL-1) induced increase in short-circuit current (Isc) was prevented by ouabain (100 microM) or removal of apical Na+. Dopamine (1 microM) applied from the apical side significantly decreased (29 +/- 5% reduction) the amphotericin B-induced increase in Isc, this being prevented by the D1-like receptor antagonist SKF 83566 (1 microM) and the protein kinase C (PKC) inhibitor chelerythrine (1 microM). Exposure of OK cells to cytochalasin B (1 microM) or cytochalasin D (1 microM), inhibitors of actin polymerization, from both cell sides reduced by 31 +/- 4% and 36 +/- 3% the amphotericin B-induced increase in Isc and abolished the inhibitory effect of apical dopamine (1 microM), but not that of the PKC activator phorbol-12,13-dibutyrate (PDBu; 100 nM). Colchicine (1 microM) failed to alter the inhibitory effects of dopamine. The relationship between Na+-K+-ATPase and the concentration of extracellular Na+ showed a Michaelis-Menten constant (Km) of 44.1 +/- 13.7 mM and a Vmax of 49.6 +/- 4.8 microA cm-2 in control monolayers. In the presence of apical dopamine (1 microM) or cytochalasin B (1 microM) Vmax values were significantly (P < 0.05) reduced without changes in Km values. These results are the first, obtained in live cells, showing that the PKC-dependent inhibition of Na+-K+-ATPase activity by dopamine requires the integrity of the association between actin cytoskeleton and Na+-K+-ATPase.
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Affiliation(s)
- P Gomes
- Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal
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Doné SC, Leibiger IB, Efendiev R, Katz AI, Leibiger B, Berggren PO, Pedemonte CH, Bertorello AM. Tyrosine 537 within the Na+,K+-ATPase alpha-subunit is essential for AP-2 binding and clathrin-dependent endocytosis. J Biol Chem 2002; 277:17108-11. [PMID: 11859087 DOI: 10.1074/jbc.m201326200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In renal epithelial cells endocytosis of Na(+),K(+)-ATPase molecules is initiated by phosphorylation of its alpha(1)-subunit, leading to activation of phosphoinositide 3-kinase and adaptor protein-2 (AP-2)/clathrin recruitment. The present study was performed to establish the identity of the AP-2 recognition domain(s) within the Na(+),K(+)-ATPase alpha(1)-subunit. We identified a conserved sequence (Y(537)LEL) within the alpha(1)-subunit that represents an AP-2 binding site. Binding of AP-2 to the Na(+),K(+)-ATPase alpha(1)-subunit in response to dopamine (DA) was increased in OK cells stably expressing the wild type rodent alpha-subunit (OK-WT), but not in cells expressing the Y537A mutant (OK-Y537A). DA treatment was associated with increased alpha(1)-subunit abundance in clathrin vesicles from OK-WT but not from OK-Y537A cells. In addition, this mutation also impaired the ability of DA to inhibit Na(+),K(+)-ATPase activity. Because phorbol esters increase Na(+),K(+)-ATPase activity in OK cells, and this effect was not affected by the Y537A mutation, the present results suggest that the identified motif is specifically required for DA-induced AP-2 binding and Na(+),K(+)-ATPase endocytosis.
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Affiliation(s)
- Stefania Cotta Doné
- Department of Molecular Medicine, Karolinska Institutet, The Rolf Luft Centrum for Diabetes Research, Karolinska Hospital, 171 76 Stockholm, Sweden
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Sweeney G, Niu W, Canfield VA, Levenson R, Klip A. Insulin increases plasma membrane content and reduces phosphorylation of Na(+)-K(+) pump alpha(1)-subunit in HEK-293 cells. Am J Physiol Cell Physiol 2001; 281:C1797-803. [PMID: 11698237 DOI: 10.1152/ajpcell.2001.281.6.c1797] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin stimulates K(+) uptake and Na(+) efflux via the Na(+)-K(+) pump in kidney, skeletal muscle, and brain. The mechanism of insulin action in these tissues differs, in part, because of differences in the isoform complement of the catalytic alpha-subunit of the Na(+)-K(+) pump. To analyze specifically the effect of insulin on the alpha(1)-isoform of the pump, we have studied human embryonic kidney (HEK)-293 cells stably transfected with the rat Na(+)-K(+) pump alpha(1)-isoform tagged on its first exofacial loop with a hemagglutinin (HA) epitope. The plasma membrane content of alpha(1)-subunits was quantitated by binding a specific HA antibody to intact cells. Insulin rapidly increased the number of alpha(1)-subunits at the cell surface. This gain was sensitive to the phosphatidylinositol (PI) 3-kinase inhibitor wortmannin and to the protein kinase C (PKC) inhibitor bisindolylmaleimide. Furthermore, the insulin-stimulated gain in surface alpha-subunits correlated with an increase in the binding of an antibody that recognizes only the nonphosphorylated form of alpha(1) (at serine-18). These results suggest that insulin regulates the Na(+)-K(+) pump in HEK-293 cells, at least in part, by decreasing serine phosphorylation and increasing plasma membrane content of alpha(1)-subunits via a signaling pathway involving PI 3-kinase and PKC.
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Affiliation(s)
- G Sweeney
- Programme in Cell Biology, Hospital for Sick Children, Toronto M5G 1X8, Canada
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