Critical role of protein kinase C α and calcium in growth factor induced activation of the Na<sup>+</sup>/H<sup>+</sup> exchanger NHE1

Maly, Karl; Strese, Kukka; Kampfer, Sonja; Ueberall, Florian; Baier, Gottfried; Ghaffari-Tabrizi, Nassim; Grunicke, H.; Leitges, Michael

doi:10.1016/s0014-5793(02)02867-3

Cited by 43 publications

(41 citation statements)

References 20 publications

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“…We cannot rule out the possibility that receptor stimulation produces different effects on PIP 2 hydrolysis from those produced by ATP depletion or treatment with exogenous phosphatase: for instance, some localized PIP 2 bound to NHE1 may not be completely hydrolyzed upon receptor stimulation and thus the NHE1 activity may be preserved, whereas localized PIP 2 may be dephosphorylated by other treatments, leading to robust inhibition of NHE1 activity. Although many studies have used PKC inhibitors to validate the involvement of PKC in NHE1 regulation (41)(42)(43)(44), the effectiveness of these inhibitors are variable. Therefore, in this study, we assessed NHE1 regulation by using only those inhibitors that completely inhibited MARCKS translocation under similar conditions.…”

Section: Discussionmentioning

confidence: 99%

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Wakabayashi

Nakamura

Kobayashi

et al. 2010

Journal of Biological Chemistry

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Protein kinase C (PKC) is considered crucial for hormonal Na؉ /H ؉ exchanger (NHE1) activation because phorbol esters (PEs) strongly activate NHE1. However, here we report that rather than PKC, direct binding of PEs/diacylglycerol to the NHE1 lipid-interacting domain (LID) and the subsequent tighter association of LID with the plasma membrane mainly underlies NHE1 activation. We show that (i) PEs directly interact with the LID of NHE1 in vitro, (ii) like PKC, green fluorescent protein (GFP)-labeled LID translocates to the plasma membrane in response to PEs and receptor agonists, (iii) LID mutations markedly inhibit these interactions and PE/receptor agonist-induced NHE1 activation, and (iv) PKC inhibitors ineffectively block NHE1 activation, except staurosporin, which itself inhibits NHE1 via LID. Thus, we propose a PKC-independent mechanism of NHE1 regulation via a PE-binding motif previously unrecognized.

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Section: Discussionmentioning

confidence: 99%

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Wakabayashi

Nakamura

Kobayashi

et al. 2010

Journal of Biological Chemistry

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“…Thus, nonspecific inhibition of p90 RSK is unlikely to have been primarily responsible for the inhibitory effects of GF109203X on the stimulation of NHE1 activity by the pertinent GPCR agonists in intact ARVM. In addition, other studies in noncardiac cell types have used alternative tools to manipulate cellular PKC activity, and have supported a role for PKC and/or specific PKC isoforms in NHE1 regulation (Chen & Wu, 1995;Maly et al, 2002). Nevertheless, further investigation, using complementary techniques, is required to confirm the involvement of PKC isoforms in the regulation of NHE1 activity in ARVM, particularly since, unlike p90 RSK (Takahashi et al, 1999), PKC isoforms do not appear to directly phosphorylate the regulatory C-terminal domain of NHE1 (Fliegel et al, 1992).…”

Section: Na Roberts Et Al Pharmacology Of Pkc Inhibitors In Cardiacmentioning

confidence: 99%

Effects of bisindolylmaleimide PKC inhibitors on p90^RSK activity in vitro and in adult ventricular myocytes

Roberts

Haworth

Avkiran

2005

British J Pharmacology

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1 Bisindolylmaleimide inhibitors of protein kinase C (PKC), such as GF109203X and Ro31-8220, have been used to investigate the roles of PKC isoforms in many cellular processes in cardiac myocytes, but these agents may also inhibit p90 RSK activity. 2 In in vitro kinase assays utilising 50 mM [ATP], GF109203X and Ro31-8220 inhibited p90 RSK isoforms (IC 50 values for inhibition of RSK1, RSK2 and RSK3, respectively, were 610, 310 and 120 nM for GF109203X, and 200, 36 and 5 nM for Ro31-8220) as well as classical and novel PKC isoforms (IC 50 values for inhibition of PKCa and PKCe, respectively, were 8 and 12 nM for GF109203X, and 4 and 8 nM for Ro31-8220). 3 At physiological [ATP] (5 mM), both GF109203X and Ro31-8220 exhibited reduced potency as inhibitors of RSK2, PKCa and PKCe (IC 50 values of 7400, 310 and 170 nM, respectively, for GF109203X, and 930, 150 and 140 nM, respectively, for Ro31-8220), with the latter agent retaining its relatively greater potency. 4 To determine the effects of GF109203X and Ro31-8220 on p90 RSK activity in cultured adult rat ventricular myocytes (ARVM), phosphorylation of the eukaryotic elongation factor 2 kinase (eEF2K) at Ser366, a known p90 RSK target, was used as the index of such activity. Adenoviral expression of a constitutively active form of mitogen-activated protein kinase (MAPK) or extracellular signalregulated kinase (ERK) kinase 1 (MEK1) was used to induce PKC-independent p90 RSK activation and downstream phosphorylation of eEF2K. 5 eEF2K phosphorylation was abolished by U0126 (1 mM), a selective inhibitor of MEK1, and was significantly reduced by GF109203X at X3 mM and by Ro31-8220 at X1 mM. At 1 mM, both agents inhibited PMA-induced PKC activity in ARVM. 6 These data show that GF109203X and Ro31-8220 inhibit various isoforms of PKC and p90 RSK in vitro and in intact ARVM, with the former agent exhibiting relatively greater selectivity for PKC.

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“…It can also cause changes in electrolyte and nutrient absorption (13,25,37). EGF stimulates NHE1 activity in the gastrointestinal tract and other organs (8,16,17,22,23). EGF also activates NHE2 function in the intestine by enhancing NHE2 gene expression (38).…”

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confidence: 99%

Epidermal growth factor inhibits intestinal NHE8 expression via reducing its basal transcription

Zhang

et al. 2010

American Journal of Physiology-Cell Physiology

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Sodium/hydrogen exchangers (NHEs) play a major role in Na ϩ absorption, cell volume regulation, and intracellular pH regulation. Of the nine identified mammalian NHEs, three (NHE2, NHE3, and NHE8) are localized on the apical membrane of epithelial cells in the small intestine and the kidney. Although the regulation of NHE2 and NHE3 expression has been extensively studied in the past decade, little is known about the regulation of NHE8 gene expression under physiological conditions. The current studies were performed to explore the role of epidermal growth factor (EGF) on NHE8 expression during intestinal maturation. Brush-border membrane vesicles (BBMV) were isolated from intestinal epithelia, and Western blot analysis was performed to determine NHE8 protein expression of sucking male rats treated with EGF. Real-time PCR was used to quantitate NHE8 mRNA expression in rats and Caco-2 cells. Human NHE8 promoter activity was characterized through transfection of Caco-2 cells. Gel mobility shift assays (GMSAs) were used to identify the promoter sequences and the transcriptional factors involved in EGF-mediated regulation. Our results showed that intestinal NHE8 mRNA expression was decreased in EGF-treated rats and Caco-2 cells, and NHE8 protein abundance was also decreased in EGF-treated rats. The activity of the human NHE8 gene promoter transfected in Caco-2 cells was also reduced by EGF treatment. This could be explained by reduced binding of transcription factor Sp3 on the NHE8 basal promoter region in the presence of EGF. Pretreatment with MEK1/2 inhibitor UO-126 could prevent EGF-mediated inhibition of NHE8 gene expression. In conclusion, this study showed that EGF inhibits NHE8 gene expression through reducing its basal transcription, suggesting an important role of EGF in regulating NHE expression during intestinal maturation. intestine; Sp3; sodium/hydrogen exchangers; Caco-2 cells SODIUM IS AN ELECTROLYTE that is essential to volume regulation and maintenance of blood pressure. Sodium absorption is mediated by several transporter families including Na . They are widely expressed in mammalian cells, with broad physiological functions including intracellular pH homeostasis, cell volume regulation, acid-base regulation, and electroneutral NaCl transport. To date, nine mammalian NHEs are discovered, and five of them (NHE1-4, 8) are located in intestinal enterocytes (36,40). These NHEs have different membrane localization and functions. NHE1 and NHE4 are expressed in the basolateral membrane of the intestinal epithelial cells (26,30,32), whereas NHE2, NHE3, and NHE8 are expressed in the brush-border membrane (BBM) of the intestinal epithelial cells (10,12,36). NHE1 contributes to cell volume regulation and intracellular pH (pH i ) regulation (26). Lack of NHE1 expression results in decreased postnatal growth rate, ataxia, and seizures (4). NHE2 is involved in gastric function. Loss of NHE2 results in altered oxyntic mucosa, markedly reduced parietal and zymogenic cell number (5, 21), and impaired intestinal barr...

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Critical role of protein kinase C α and calcium in growth factor induced activation of the Na⁺/H⁺ exchanger NHE1

Cited by 43 publications

References 20 publications

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Effects of bisindolylmaleimide PKC inhibitors on p90^RSK activity in vitro and in adult ventricular myocytes

Epidermal growth factor inhibits intestinal NHE8 expression via reducing its basal transcription

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Critical role of protein kinase C α and calcium in growth factor induced activation of the Na+/H+ exchanger NHE1

Cited by 43 publications

References 20 publications

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Novel Phorbol Ester-binding Motif Mediates Hormonal Activation of Na+/H+ Exchanger

Effects of bisindolylmaleimide PKC inhibitors on p90RSK activity in vitro and in adult ventricular myocytes

Epidermal growth factor inhibits intestinal NHE8 expression via reducing its basal transcription

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Product

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Critical role of protein kinase C α and calcium in growth factor induced activation of the Na⁺/H⁺ exchanger NHE1

Effects of bisindolylmaleimide PKC inhibitors on p90^RSK activity in vitro and in adult ventricular myocytes