Stimulation of the Plasma Membrane Na+/H+ Exchanger NHE1 by Sustained Intracellular Acidosis

Haworth, Robert S.; McCann, C.K.; Snabaitis, Andrew K.; Roberts, Neil; Avkiran, Metin

doi:10.1074/jbc.m304400200

Cited by 101 publications

(131 citation statements)

References 42 publications

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“…We found that this method of stimulation of these cells resulted in increased activity and phosphorylation of the protein that could be blocked by MEK inhibition. Our results on stimulation of activity of NHE1 were similar to those of Haworth et al (17). It should be noted that our results differ from those Hayashi et al (22), who did not find that sustained intracellular acidosis stimulates NHE1 activity.…”

Section: /Hsupporting

confidence: 51%

“…We examined ERK-dependent phosphorylation because in several earlier studies we have shown both ERK-dependent phosphorylation of the NHE1 protein and ERKdependent stimulation of activity (10,11). Sustained intracellular acidosis was earlier shown to be a reliable method of stimulation of Na ϩ /H ϩ exchanger activity by ERK-dependent pathways (17). In preliminary experiments we found that it was a more reliable method of activation of NHE1 in this cell type in comparison with receptor-mediated activation.…”

Section: /Hmentioning

confidence: 91%

“…Following the pH i recovery, a three-point pH calibration using Na ϩ -free calibration buffers (135 mM N-methyl glucamine, 135 mM KCl, 1.8 mM CaCl 2 , 1 mM MgSO 4 , 5.5 mM glucose, 10 mM HEPES, at pH 6, 7, and 8) was completed. For some experiments we used a two-pulse assay to induce prolonged intracellular acidosis (17) and to stimulate ERK-dependent pathways and the activity of NHE1. For these experiments the cells were initially acidified with ammonium chloride as described above and then immediately allowed to recover in normal Na ϩ -containing medium.…”

Section: * This Work Was Supported By a Grant From The Canadian Instimentioning

confidence: 99%

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Mitogen-activated Protein Kinase-dependent Activation of the Na+/H+ Exchanger Is Mediated through Phosphorylation of Amino Acids Ser770 and Ser771

Malo¹,

Fliegel³

2007

Journal of Biological Chemistry

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We investigated regulation of the type 1 isoform of the Na ؉ /H ؉ exchanger by phosphorylation. Four specific groups of serine and threonine residues in the regulatory carboxyl-terminal tail were mutated to alanine residues: group 1, S693A; group 2, T718A and S723A/S726A/S729A; group 3, S766A/S770A/ S771A; and group 4, T779A and S785A. The proteins were expressed in Na ؉ /H ؉ exchanger-deficient cells, and the activity was characterized. All of the mutants had proper expression, localization, and normal basal activity relative to wild type NHE1. Sustained intracellular acidosis was used to activate NHE1 via an ERK-dependent pathway that could be blocked with the MEK inhibitor U0126.

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Section: /Hsupporting

confidence: 51%

Section: /Hmentioning

confidence: 91%

Section: * This Work Was Supported By a Grant From The Canadian Instimentioning

confidence: 99%

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Mitogen-activated Protein Kinase-dependent Activation of the Na+/H+ Exchanger Is Mediated through Phosphorylation of Amino Acids Ser770 and Ser771

Malo¹,

Fliegel³

2007

Journal of Biological Chemistry

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“…This activates the plasmalemmal Na + /Ca ++ exchanger inducing a deleterious increase of intracellular Ca ++ that triggers various pathways ultimately leading to cell death [74,99,98,77]. Genetic ablation or pharmalogic inhibition of NHE1 during episodes of ischemiareperfusion mitigated cardiac and neural injuries both in vivo and in vitro in rodents and pigs [85,32,62]. Consistent with this, NHE1 overactivity has been linked to cardiac hypertrophy and heart failure [168].…”

Section: Slc9a1-nhe1mentioning

confidence: 76%

Traditional and emerging roles for the SLC9 Na+/H+ exchangers

Fuster

Alexander

2013

Pflugers Arch - Eur J Physiol

143

122

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The SLC9 gene family encodes Na + /H + exchangers (NHEs). These transmembrane proteins transport ions across lipid bilayers in a diverse array of species from prokaryotes to eukaryotes, including plants, fungi and animals. They utilize the electrochemical gradient of one ion to transport another ion against its electrochemical gradient. Currently, 13 evolutionarily conserved NHE isoforms are known in mammals [46,22,128]. The SLC9 gene family (solute carrier classification of transporters:www.bioparadigms.org) is divided into three subgroups [46]. The SLC9A subgroup encompasses plasmalemmal isoforms NHE1-5 (SLC9A1-5) and the predominantly intracellular isoforms NHE6-9 (SLC9A6-9). The SLC9B subgroup consists of two recently cloned isoforms, NHA1 and NHA2 (SLC9B1 and SLC9B2, respectively). The SLC9C subgroup consist of a sperm specific plasmalemmal NHE (SLC9C1) and a putative NHE, SLC9C2, for which there is currently no functional data [46].NHEs participate in the regulation of cytosolic and organellar pH as well as cell volume. In the intestine and kidney, NHEs are critical for transepithelial movement of Na + and HCO 3 -and thus for whole body volume and acid-base homeostasis [46]. Mutations in the NHE6 or NHE9 genes cause neurological disease in humans and are currently the only NHEs directly linked to human disease.However, it is becoming increasingly apparent that members of this gene family contribute to the pathophysiology of multiple human diseases.

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“…Prolonged Acidosis Is Not Responsible for NHE1 Activation following OGD/REOX-It has been reported that prolonged acidosis (pH i of 6.55) for 3 min in rat ventricular cardiomyocytes leads to ERK1/2-dependent stimulation of NHE1 activity (26). 2 h OGD reduced basal pH i from 7.09 to 6.80 in astrocytes (6).…”

Section: Nhe1 Kinase P90 Rsk Is Downstream Effector Of Erk1/2-p90mentioning

confidence: 99%

ERK1/2-p90RSK-mediated Phosphorylation of Na+/H+ Exchanger Isoform 1

Luo

Kintner

Shull

et al. 2007

Journal of Biological Chemistry

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The function and regulation of Na ؉ /H ؉ exchanger isoform 1 (NHE1) following cerebral ischemia are not well understood. In this study, we demonstrate that extracellular signal-related kinases (ERK1/2) play a role in stimulation of neuronal NHE1 following in vitro ischemia. NHE1 activity was significantly increased during 10 -60 min reoxygenation (REOX) after 2-h oxygen and glucose deprivation (OGD). OGD/REOX not only increased the V max for NHE1 but also shifted the K m toward decreased [H ؉ ] i . These changes in NHE1 kinetics were absent when MAPK/ERK kinase (MEK) was inhibited by the MEK inhibitor U0126. There were no changes in the levels of phosphorylated ERK1/2 (p-ERK1/2) after 2 h OGD. The p-ERK1/2 level was significantly increased during 10 -60 min REOX, which was accompanied by nuclear translocation. U0126 abolished REOX-induced elevation and translocation of p-ERK1/2. We further examined the ERK/90-kDa ribosomal S6 kinase (p90 RSK ) signaling pathways. At 10 min REOX, phosphorylated NHE1 was increased with a concurrent elevation of phosphorylation of p90 RSK , a known NHE1 kinase. Inhibition of MEK activity with U0126 abolished phosphorylation of both NHE1 and p90 RSK . Moreover, neuroprotection was observed with U0126 or genetic ablation or pharmacological inhibition of NHE1 following OGD/REOX. Taken together, these results suggest that activation of ERK1/2-p90 RSK pathways following in vitro ischemia phosphorylates NHE1 and increases its activity, which subsequently contributes to neuronal damage. The Naϩ /H ϩ exchanger (NHE) 2 family is a group of membrane transport proteins that catalyzes the secondary active electroneurtral exchange of one Na ϩ for one H ϩ . To date, nine NHE isoforms (NHE1-9) have been cloned in mammalian tissues (1). Na ϩ /H ϩ exchanger isoform 1 (NHE1) is the most abundant NHE isoform in the rat central nervous system (2) and crucial in regulation of neuronal pH i (3, 4). We have recently reported that NHE1 activity plays an important role in neuronal damage in both in vitro and in vivo ischemic models (4). Inhibition of NHE1 activity during OGD/REOX prevents intracellular Na ϩ and Ca 2ϩ overload and thus reduces the Ca 2ϩ -mediated cascade of deleterious events (4). In acutely isolated CA1 neurons, an anoxia-triggered intracellular alkalization depends on activation of NHE1 (5). We also found that NHE1 activity is stimulated in cortical astrocytes following in vitro ischemia (6). However, whether NHE1 activity is overstimulated in cortical neurons following in vitro ischemia remains unknown.NHE1 has two large functional domains. The N-terminal transmembrane domain (ϳ500 amino acids) is responsible for cation translocation, and the cytoplasmic C-terminal domain (ϳ315 amino acids) is the main regulatory site for the NHE1 activity (7). The distal C-terminal tail of NHE1 contains a number of serine and threonine residues that are phosphorylated by several protein kinases, including extracellular signal-related kinases (ERK1/2) and 90-kDa ribosomal S6 kinase (p90 RSK ) (8). Activa...

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Stimulation of the Plasma Membrane Na+/H+ Exchanger NHE1 by Sustained Intracellular Acidosis

Cited by 101 publications

References 42 publications

Mitogen-activated Protein Kinase-dependent Activation of the Na+/H+ Exchanger Is Mediated through Phosphorylation of Amino Acids Ser770 and Ser771

Mitogen-activated Protein Kinase-dependent Activation of the Na+/H+ Exchanger Is Mediated through Phosphorylation of Amino Acids Ser770 and Ser771

Traditional and emerging roles for the SLC9 Na+/H+ exchangers

ERK1/2-p90RSK-mediated Phosphorylation of Na+/H+ Exchanger Isoform 1

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