scholarly journals AT1 receptor-mediated accumulation of extracellular angiotensin II in proximal tubule cells: role of cytoskeleton microtubules and tyrosine phosphatases

2006 ◽  
Vol 291 (2) ◽  
pp. F375-F383 ◽  
Author(s):  
Xiao C. Li ◽  
Oscar A. Carretero ◽  
L. Gabriel Navar ◽  
Jia L. Zhuo
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Tyrosine Phosphatase ◽  
Camp Signaling ◽  
Intracellular Camp ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Receptor Mediated Endocytosis ◽  
Tubule Cells ◽  
Cytoskeleton Microtubule

Long-term angiotensin II (ANG II) administration is associated with increased ANG II accumulation in the kidney, but intrarenal compartment(s) involved in this response remains to be determined. We tested the hypothesis that 1) extracellular ANG II is taken up by proximal tubule cells (PTCs) through AT1 receptor-mediated endocytosis, 2) this process is regulated by cytoskeleton microtubule- and tyrosine phosphatase-dependent mechanisms, and 3) AT1 receptor-mediated endocytosis of ANG II has a functional relevance by modulating intracellular cAMP signaling. In cultured PTCs, [125I]Tyr-labeled ANG II and fluorescein labeled-ANG II were internalized in a time-dependent manner and colocalized with the endosome marker Alexa Fluor 594-transferrin. Endocytosis of extracellular ANG II was inhibited by the AT1 receptor blocker losartan (16.5 ± 4.6%, P < 0.01 vs. ANG II, 78.3 ± 6.2%) and by the tyrosine phosphatase inhibitor phenylarsine oxide (PAO; 30.0 ± 3.5%, P < 0.05 vs. ANG II). Intracellular ANG II levels were increased by ∼58% (basal, 229.8 ± 11.4 vs. ANG II, 361.3 ± 11.8 pg ANG II/mg protein, P < 0.01), and the responses were blocked by losartan ( P < 0.01), the cytoskeleton microtubule inhibitor colchicine ( P < 0.05), and PAO ( P < 0.01), whereas depletion of clathrin-coated pits with hyperosmotic sucrose had no effect (356.1 ± 25.5 pg ANG II/mg protein, not significant). ANG II accumulation was associated with significant inhibition of both basal (control, 15.5 ± 2.8 vs. ANG II, 9.1 ± 2.4 pmol/mg protein, P < 0.05) and forskolin-stimulated cAMP signaling (forskolin, 68.7 ± 8.6 vs. forskolin + ANG II, 42.8 ± 13.8 pmol/mg protein, P < 0.01). These effects were blocked by losartan and PAO. We conclude that extracellular ANG II is internalized in PTCs through AT1 receptor-mediated endocytosis and that internalized ANG II may play a functional role in proximal tubule cells by inhibiting intracellular cAMP signaling.

Angiotensin II-dependent proximal tubule sodium transport requires receptor-mediated endocytosis

1994 ◽  
Vol 266 (3) ◽  
pp. C669-C675 ◽  
Author(s):  
J. R. Schelling ◽  
S. L. Linas
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Receptor Internalization ◽  
Ang Ii ◽  
Na Transport ◽  
Cellular Mechanisms ◽  
Transport Pathways ◽  
Proximal Tubule Cells ◽  
Receptor Mediated Endocytosis ◽  
Tubule Cells

Angiotensin II (ANG II) receptors are present on apical and basolateral surfaces of proximal tubule cells. To determine the cellular mechanisms of proximal tubule ANG II receptor-mediated Na transport, apical-to-basolateral 22Na flux was measured in cultured proximal tubule cells. Apical ANG II caused increases in 22Na flux (maximum response: 100 nM, 30 min). Basolateral ANG II resulted in 22Na flux that was 23-56% greater than 22Na flux observed with equimolar apical ANG II. Apical ANG II-induced 22Na flux was prevented by preincubation with amiloride, ouabain, and the AT1 receptor antagonist losartan. Because apical ANG II signaling was previously shown to be endocytosis dependent, we questioned whether endocytosis was required for ANG II-stimulated proximal tubule Na transport as well. Apical (but not basolateral) ANG II-dependent 22Na flux was inhibited by phenylarsine oxide, an agent which prevents ANG II receptor internalization. In conclusion, apical and basolateral ANG II caused proximal tubule Na transport. Apical ANG II-dependent Na flux was mediated by AT1 receptors, transcellular transport pathways, and receptor-mediated endocytosis.

Angiotensin II AT2 receptors inhibit growth responses in proximal tubule cells

2001 ◽  
Vol 281 (2) ◽  
pp. F300-F308 ◽  
Author(s):  
Joseph Zimpelmann ◽  
Kevin D. Burns
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Receptor Activation ◽  
Proximal Tubule Cell ◽  
Ang Ii ◽  
Phosphotyrosine Phosphatase ◽  
Proximal Tubule Cells ◽  
Transfected Cells ◽  
Mapk Activity ◽  
Tubule Cells

Angiotensin II (ANG II) subtype 2 (AT2) receptors are expressed in the adult kidney, but the effects of AT2 receptor activation are unclear. The proximal tubule cell line LLC-PK1 was transfected with a plasmid containing cDNA for the rat AT2 receptor. In transfected cells, specific binding of 125I-labeled ANG II was detected (dissociation constant = 0.81 nM), with inhibition by the AT2 antagonist PD-123319, and no effect of the AT1 antagonist losartan. ANG II (10−7 M) significantly inhibited mitogen-activated protein kinase (MAPK) activity in transfected cells, associated with decreased phosphorylation of the extracellular signal-related kinases ERK1 and ERK2. ANG II stimulated phosphotyrosine phosphatase activity within 5 min, an effect blocked by PD-123319 and the phosphatase inhibitor vanadate. In transfected cells, ANG II inhibited epidermal growth factor-stimulated [3H]thymidine incorporation, an effect reversed by vanadate. In contrast, vanadate did not block ANG II-stimulated apoptosis of transfected cells. In summary, AT2 receptors in proximal tubule cells inhibit MAPK activity and stimulate phosphotyrosine phosphatase. AT2receptor-induced inhibition of mitogenesis is mediated by phosphatase activation, whereas effects on apoptosis are insensitive to phosphatase inhibition. The data suggest that AT2 receptors inhibit cell growth via distinct signaling pathways in the proximal tubule.

scholarly journals Angiotensin II counteracts the effects of cAMP/PKA on NHE3 activity and phosphorylation in proximal tubule cells

2016 ◽  
Vol 311 (5) ◽  
pp. C768-C776 ◽  
Author(s):  
Renato O. Crajoinas ◽  
Juliano Z. Polidoro ◽  
Carla P. A. Carneiro de Morais ◽  
Regiane C. Castelo-Branco ◽  
Adriana C. C. Girardi
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Intracellular Camp ◽  
Camp Accumulation ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Opossum Kidney ◽  
Subsequent Decrease

Binding of angiotensin II (ANG II) to the AT1 receptor (AT1R) in the proximal tubule stimulates Na+/H+ exchanger isoform 3 (NHE3) activity through multiple signaling pathways. However, the effects of ANG II/AT1R-induced inihibitory G protein (Gi) activation and subsequent decrease in cAMP accumulation on NHE3 regulation are not well established. We therefore tested the hypothesis that ANG II reduces cAMP/PKA-mediated phosphorylation of NHE3 on serine 552 and, in doing so, stimulates NHE3 activity. Under basal conditions, ANG II stimulated NHE3 activity but did not affect PKA-mediated NHE3 phosphorylation at serine 552 in opossum kidney (OKP) cells. However, in the presence of the cAMP-elevating agent forskolin (FSK), ANG II blocked FSK-induced NHE3 inhibition, reduced intracellular cAMP concentrations, lowered PKA activity, and prevented the FSK-mediated increase in NHE3 serine 552 phosphorylation. All effects of ANG II were blocked by pretreating OKP cells with the AT1R antagonist losartan, highlighting the contribution of the AT1R/Gi pathway in ANG II-mediated NHE3 upregulation under cAMP-elevating conditions. Accordingly, Gi inhibition by pertussis toxin treatment decreased NHE3 activity both in vitro and in vivo and, more importantly, prevented the stimulatory effect of ANG II on NHE3 activity in rat proximal tubules. Collectively, our results suggest that ANG II counteracts the effects of cAMP/PKA on NHE3 phosphorylation and inhibition by activating the AT1R/Gi pathway. Moreover, these findings support the notion that NHE3 dephosphorylation at serine 552 may represent a key event in the regulation of renal proximal tubule sodium handling by ANG II in the presence of natriuretic hormones that promote cAMP accumulation and transporter phosphorylation.

scholarly journals ANGIOTENSIN II (ANG II) MODULATES RESPONSE TO OXIDANT INJURY IN IMMORTALIZED RAT PROXIMAL TUBULE CELLS (IRPTC). † 2157

1996 ◽  
Vol 39 ◽  
pp. 362-362
Author(s):  
Julie R Ingelfinger ◽  
Liam Haveran ◽  
Dan Diamant ◽  
Flavia F Jung ◽  
Shiow-Shih Tang
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Ang Ii ◽  
Oxidant Injury ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Rat Proximal Tubule

Angiotensin II stimulation of Na(+)-H+ exchange in proximal tubule cells

1990 ◽  
Vol 258 (5) ◽  
pp. F1188-F1195 ◽  
Author(s):  
G. Saccomani ◽  
K. D. Mitchell ◽  
L. G. Navar
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Initial Rate ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Intact Rabbit ◽  
Rate Of Recovery ◽  
Tubule Cells ◽  
22Na Uptake ◽  
Intracellular Alkalinization

Experiments were performed to evaluate the effect of angiotensin II (ANG II) on the sodium transport activity of isolated intact rabbit proximal tubule cells. Initial rates of 22Na(+) uptake were measured in Na+-depleted and ouabain-treated cells in the presence of an opposing H+ gradient (pHin less than pHout). ANG II (10(-12)-10(-9) M) stimulated the initial rate of 22Na+ uptake by 33 +/- 2%, whereas amiloride (0.5 mM) inhibited both basal and ANG II-stimulated 22Na+ uptake. ANG II-stimulated rate of 22Na+ uptake was inhibited by the receptor antagonist saralasin. Additional experiments were performed to evaluate the effect of ANG II on the rate of recovery of pHin in acid-loaded proximal tubule cells. Cells were acid loaded by an NH4Cl pulse in the presence of the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. ANG II increased the initial rate of intracellular alkalinization, and this effect was inhibited by amiloride (1.0 mM). ANG II stimulation increased the Vmax of H+ efflux (from 0.53 +/- 0.02 to 0.64 +/- 0.04 pH units/min) without changing the Km for extracellular Na+. The present findings indicate that physiological concentrations of ANG II stimulate an amiloride-sensitive Na+-H+ antiport in proximal tubule cells.

Abstract 009: Mitochondria-targeting Overexpression of AT 2 Receptors Inhibits Intracellular Angiotensin II-induced Respiratory and Glycolytic Stress Responses in Mouse Proximal Tubule Cells

Hypertension ◽  
2017 ◽  
Vol 70 (suppl_1) ◽  
Author(s):  
Xiao C Li ◽  
Jia L Zhuo
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Stress Responses ◽  
Stress Test ◽  
Fluorescent Imaging ◽  
Complex Iii ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Mitochondrial Respiratory

Angiotensin II (ANG II) plays an important role in mitochondrial dysfunction associated with cardiovascular, hypertensive and kidney diseases, but it is not known whether extracellular or intracellular ANG II mediates this effect via activation of cell surface or mitochondrial receptors. As a proof of concept study, we overexpressed an intracellular cyan fluorescent ANG II fusion protein, mito-ANG II, with or without a GFP-tagged full length AT 2 receptor, mito-AT 2 R, selectively in the mitochondria of mouse proximal tubule (mPCT) cells. The mitochondrial respiratory and glycolytic stress responses were measured using Seahorse XF Cell Mito and XF Glycolysis Stress Test Kits, respectively. Live cell fluorescent imaging confirmed the expression and colocalization of mito-ANG II and mito-AT 2 R with a mitochondrial marker MitoTracker®. Overexpression of mito-ANG II for 48 h significantly increased mitochondrial oxygen consumption rate (OCR) by 30% (Control: 239.4 ± 9.2 vs. mito-ANG II: 310.4 ± 12.6 pmol/min; p <0.01, n=5) and extracellular acidification rate (ECAR) by 33% (Control: 6.3 ± 0.3 vs. mito-ANG II: 8.1 ± 0.5 mpH/min; p <0.01, n=5). The effects of mito-ANG II on OCR and ECAR responses were associated with significant increases in phosphorylated MAP kinase ERK1/2, Na + /K + -ATPase, and mitochondrial redox carries, Complex I (NADH coenzyme Q reductase), Complex II (succinate dehydrogenase), Complex III (cytochrome bc 1 complex) and Complex IV (cytochrome c oxidase) ( p <0.01, n=6). The mito-ANG II-induced OCR and ECAR responses were blocked by the AT 1 blocker losartan (10 μM, p <0.01, n=5), but not by the AT 2 receptor blocker PD123319 (10 μM, n.s. , n=5). However, concurrent overexpression of mito-AT 2 R with mito-ANG II in the mitochondria of mPCT cells significantly attenuated the effects of mito-ANG II on OCR and ECAR responses ( p <0.01, n=6), while the effects of mito-AT 2 R overexpression were completely blocked by PD123319 ( p <0.01, n=5). Taken together, our results provide strong evidence that activation of mitochondrial AT 1 receptors by intracellular ANG II stimulates, whereas activation of mitochondrial AT 2 receptors by intracellular ANG II inhibits, mitochondrial respiratory and glycolytic responses in mouse proximal tubule cells.

scholarly journals Antenatal glucocorticoid treatment alters Na+ uptake in renal proximal tubule cells from adult offspring in a sex-specific manner

2015 ◽  
Vol 308 (11) ◽  
pp. F1268-F1275 ◽  
Author(s):  
Yixin Su ◽  
Jianli Bi ◽  
Victor M. Pulgar ◽  
Jorge Figueroa ◽  
Mark Chappell ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Fetal Programming ◽  
Specific Effect ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
Female Sheep ◽  
Male Sheep ◽  
In Cells

We have shown a sex-specific effect of fetal programming on Na+ excretion in adult sheep. The site of this effect in the kidney is unknown. Therefore, we tested the hypothesis that renal proximal tubule cells (RPTCs) from adult male sheep exposed to betamethasone (Beta) before birth have greater Na+ uptake than do RPTCs from vehicle-exposed male sheep and that RPTCs from female sheep similarly exposed are not influenced by antenatal Beta. In isolated RPTCs from 1- to 1.5-yr-old male and female sheep, we measured Na+ uptake under basal conditions and after stimulation with ANG II. To gain insight into the mechanisms involved, we also measured nitric oxide (NO) levels, ANG II receptor mRNA levels, and expression of Na+/H+ exchanger 3. Basal Na+ uptake increased more in cells from Beta-exposed male sheep than in cells from vehicle-exposed male sheep (400% vs. 300%, P < 0.00001). ANG II-stimulated Na+ uptake was also greater in cells from Beta-exposed males. Beta exposure did not increase Na+ uptake by RPTCs from female sheep. NO production was suppressed more by ANG II in RPTCs from Beta-exposed males than in RPTCs from either vehicle-exposed male or female sheep. Our data suggest that one site of the sex-specific effect of Beta-induced fetal programming in the kidney is the RPTC and that the enhanced Na+ uptake induced by antenatal Beta in male RPTCs may be related to the suppression of NO in these cells.

Sign in / Sign up

Export Citation Format

Share Document