RhoA and Rho Kinase Regulate the Epithelial Na+/H+ Exchanger NHE3

Szászi, Katalin; Kurashima, Kazuyoshi; Kapùs, András; Paulsen, Anders; Kaibuchi, Kozo; Grinstein, Sergio; Orlowski, John

doi:10.1074/jbc.m001193200

Cited by 60 publications

(19 citation statements)

References 42 publications

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“…These data suggest that, in intact epithelial monolayers, ezrin phosphorylation after initiation of Na ϩ -glucose cotransport requires Akt activity. Rho kinase is known to phosphorylate ezrin (9) and has also been implicated in NHE3 inhibition (22,41). Thus, we considered the possibility that rho kinase regulates the coordinate activation of ezrin and NHE3 after initiation of Na ϩ -glucose cotransport.…”

Section: Akt Inhibition Prevents Ezrin Phosphorylation After Initiatimentioning

confidence: 99%

“…For example, NHE3 knockout mice suffer from mild diarrhea and are acidotic and hypotensive (20). NHE3 activity can be regulated by the actin cytoskeleton (21)(22)(23). Although this may be caused in part by regulation of NHE3 at the plasma membrane, it is also clear that translocation of NHE3 to the plasma membrane contributes significantly to NHE3 up-regulation (24,25).…”

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confidence: 99%

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Akt2 Phosphorylates Ezrin to Trigger NHE3 Translocation and Activation

Shiue

Musch

Wang

et al. 2005

Journal of Biological Chemistry

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Initiation of Na؉ -glucose cotransport in intestinal absorptive epithelia causes NHE3 to be translocated to the apical plasma membrane, leading to cytoplasmic alkalinization. We reported recently that this NHE3 translocation requires ezrin phosphorylation. However, the kinase that phosphorylates ezrin in this process has not been identified. Because Akt has also been implicated in NHE3 translocation, we investigated the hypothesis that Akt phosphorylates ezrin. After initiation of Na ؉ -glucose cotransport, Akt is activated with kinetics that parallel those of ezrin phosphorylation. Inhibition of p38 MAP kinase, which blocks ezrin phosphorylation, also prevents Akt activation. Purified Akt directly phosphorylates recombinant ezrin at threonine 567 in vitro in an ATP-dependent manner. This in vitro phosphorylation can be prevented by Akt inhibitors. In intact cells, inhibition of either phosphoinositide 3-kinase, an upstream regulator of Akt, or inhibition of Akt itself using inhibitors validated in vitro prevents ezrin phosphorylation after initiation of Na ؉ -glucose cotransport. Specific small interfering RNA knockdown of Akt2 prevented ezrin phosphorylation in intact cells. Pharmacological Akt inhibition or Akt2 knockdown also prevented NHE3 translocation and activation after initiation of Na ؉ -glucose cotransport, confirming the functional role of Akt2. These studies therefore identify Akt2 as a critical kinase that regulates ezrin phosphorylation and activation. This Akt2-dependent ezrin phosphorylation leads to NHE3 translocation and activation.

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Section: Akt Inhibition Prevents Ezrin Phosphorylation After Initiatimentioning

confidence: 99%

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confidence: 99%

Akt2 Phosphorylates Ezrin to Trigger NHE3 Translocation and Activation

Shiue

Musch

Wang

et al. 2005

Journal of Biological Chemistry

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“…6K and O). It has been reported that ROCK1 phosphorylates and activates Na + /H + exchanger isoform 1, NHE1 Denker et al, 2000) and that Rho-kinases inhibit the activity of Na + /H + exchanger isoform 3 (NHE3), another type of ion exchanger (Szászi et al, 2000). Because NHE1 and NHE3 are localized on the plasma membrane in MDCK cells (Noel et al, 1996) and NHE1 is in the mouse endometrial epithelium (Wang et al, 2003), it is likely that the ROCK1 localized on the plasma membrane may participate in phosphorylating these substrates.…”

Section: Plasma Membranementioning

confidence: 99%

Distinct Distribution and Localization of Rho-kinase in Mouse Epithelial, Muscle and Neural Tissues

Iizuka

Kimura

Wang

et al. 2012

Cell Struct. Funct.

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ABSTRACT. The small GTP-binding protein Rho plays a crucial role in a wide variety of cellular functions through various effector proteins. Rho-kinase is a key effector protein of Rho, which is composed of two isoforms, ROCK1 and ROCK2. To clarify the site of action of ROCK1 and ROCK2, we performed immunofluorescence and immunoelectron microscopic analyses using isoform-specific antibodies in mouse tissues. In the large and small intestines, ROCK1 immunoreactivity was predominantly identified in epithelial cells, and ROCK2 immunoreactivity was negligible. In these epithelial cells, ROCK1 immunoreactivity was distributed on plasma membranes, while ROCK1 immunogold signals were localized at cell-cell contacts and cell adhesion sites, especially at the adherens junctions at the ultrastructural level. In the bladder epithelium, however, ROCK1 and ROCK2 signals were identified at intermediate filaments, and ROCK2 signals were also observed in nuclei. In the three types of muscular cells-smooth, cardiac, and skeletal muscle cells-ROCK1 and ROCK2 also showed differential distribution. ROCK1 signals were localized at actin filaments, plasma membranes, and vesicles near plasma membranes in smooth muscle cells; at the lysosomes in skeletal muscle cells; and were undetectable in cardiac muscle cells. ROCK2 signals were localized at actin filaments and centrosomes in smooth muscle cells, at intercalated discs in cardiac muscle cells, and at Z-discs and sarcoplasmic reticulum in skeletal muscle cells. In the brain, ROCK1 immunoreactivity was distributed in glia, whereas ROCK2 immunoreactivity was observed in neurons. These results indicate that the two isoforms of Rho-kinase distribute differentially to accomplish their specific functions.

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“…However, the mechanisms by which DA acutely reduces NHE3 activity have not been examined. Redistribution of NHE3 transporters has been shown to mediate regulation of NHE3 activity in intact kidney (48 -54), in cultured renal epithelial cells (55,56), and in transfected fibroblasts (57)(58)(59)(60)(61)(62)(63)(64). In addition, although NHE phosphorylation has been associated with changes in NHE3 activity (52,(65)(66)(67)(68), and phosphorylation appears to be functionally important for regulation of NHE3 activity by pharmacologic activators of protein kinases in transfected fibroblasts (65)(66)(67), the physiologic significance of NHE3 phosphorylation is still undetermined.…”

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confidence: 99%

Dopamine Acutely Stimulates Na+/H+Exchanger (NHE3) Endocytosis via Clathrin-coated Vesicles

Hu¹,

Fan²,

Crowder³

et al. 2001

Journal of Biological Chemistry

138

167

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Extracellular fluid volume and to a certain extent blood pressure in mammals are determined by the balance between sodium intake and renal sodium excretion (1, 2). As regulator of sodium excretion, the intrarenal autocrine-paracrine dopamine (DA) 1 system assumes far greater importance than circulating endocrine or neurogenic dopamine (3-6). DA is produced in the proximal tubule via decarboxylation of its precursor L-dihydroxyphenylalanine derived from the plasma and glomerular filtrate (7-9) and is then secreted into the tubular lumen where it exerts its effects on multiple nephron segments, which cumulates in inhibition of tubular sodium absorption and natriuresis. Renal DA synthesis and excretion are increased by increased dietary salt and an intravenous saline load (10 -13), and blockade of DA synthesis or DA receptor significantly blunts the natriuretic response (14 -18). Quantitatively, the most significant inhibition of sodium transport occurs in the proximal tubule. DA inhibits proximal tubule sodium absorption partially by hemodynamic alterations (19 -22), but the major effect is directly on the tubule epithelium (23-26) via inhibition of two principal sodium transporters: the apical membrane Na ϩ /K ϩ exchanger (NHE3) (27-33) and the basolateral Na ϩ ,K ϩ -ATPase (34 -38). These effects are mediated by the DA receptor where five molecular isoforms (DR 1 -like receptors: DR 1 and DR 5 , and DR 2 -like receptors DR 2 , DR 3 , and DR 4 ) have been identified to date; all five isoforms are known to be present in the renal tubular epithelium (39 -43).Previous studies in isolated apical membrane vesicles have shown that DA inhibits proximal tubule apical membrane Na ϩ /H ϩ exchange activity mainly via DR 1 -like receptors (25-28, 30, 31, 33) through both PKA-dependent and PKA-independent mechanisms (27, 31). The Na ϩ /H ϩ exchanger on the apical membrane of the renal proximal tubule is encoded by NHE3 (44 -46), one of the seven members of the NHE gene family (47). We have shown in opossum kidney (OK) cells that the DA 1 -like and DA 2 -like receptors have synergistic actions on NHE3 activity and that inhibition of NHE3 activity by DA is accompanied by complex changes in NHE3 phosphorylation and dephosphorylation (33). However, the mechanisms by which DA acutely reduces NHE3 activity have not been examined. Redistribution of NHE3 transporters has been shown to mediate regulation of NHE3 activity in intact kidney (48 -54), in cultured renal epithelial cells (55,56), and in transfected fibroblasts (57-64). In addition, although NHE phosphorylation has been associated with changes in NHE3 activity (52,(65)(66)(67)(68), and phosphorylation appears to be functionally important for regulation of NHE3 activity by pharmacologic activators of protein kinases in transfected fibroblasts (65-67), the physiologic significance of NHE3 phosphorylation is still undetermined. In this paper we characterize one mechanism by which DA acutely inhibits NHE3: the internalization of NHE3 secondary to PKA-mediated NHE3 phosphorylatio...

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RhoA and Rho Kinase Regulate the Epithelial Na+/H+ Exchanger NHE3

Cited by 60 publications

References 42 publications

Akt2 Phosphorylates Ezrin to Trigger NHE3 Translocation and Activation

Akt2 Phosphorylates Ezrin to Trigger NHE3 Translocation and Activation

Distinct Distribution and Localization of Rho-kinase in Mouse Epithelial, Muscle and Neural Tissues

Dopamine Acutely Stimulates Na+/H+Exchanger (NHE3) Endocytosis via Clathrin-coated Vesicles

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