Gβ regulation of Na/H exchanger-3 activity in rat renal proximal tubules during development

2000 ◽  
Vol 278 (4) ◽  
pp. R931-R936 ◽  
Author(s):  
Xiao Xi Li ◽  
Frederick E. Albrecht ◽  
Jean E. Robillard ◽  
Gilbert M. Eisner ◽  
Pedro A. Jose
Keyword(s):  
G Protein ◽  
Second Messengers ◽  
Membrane Vesicles ◽  
Inhibitory Effect ◽  
Protein Subunit ◽  
Adult Rats ◽  
Renal Brush Border Membrane ◽  
Sodium Hydrogen Exchanger ◽  
Old Rats ◽  
Renal Tubular

The decreased natriuretic action of dopamine in the young has been attributed to decreased generation of cAMP by the activated renal D1-like receptor. However, sodium/hydrogen exchanger (NHE) 3 activity in renal brush-border membrane vesicles (BBMV) can be modulated independent of cytoplasmic second messengers. We therefore studied D1-like receptor regulation of NHE activity in BBMVs in 2-, 4-, and 12-wk-old (adult) rats. Basal NHE activity was least in 2-wk-old compared with 4- and 12-wk-old rats. D1-like agonist (SKF-81297) inhibition of NHE activity was also least in 2-wk-old (−1 ± 9%, n = 3) compared with 4 (−15 ± 5%, n = 6)- and 12 (−65 ± 4%, n = 6)-wk-old rats. The decreased response to the D1-like agonist in BBMV was not caused by decreased D1 receptors or NHE3 expression in the young. Gsα, which inhibits NHE3 activity by itself, coimmunoprecipitated with NHE3 to the same extent in 2-wk-old and adult rats. Gsα function was also not impaired in the young because guanosine 5′- O-(3-thiotriphosphate) decreased NHE activity to a similar extent in 4-wk-old and adult rats. Gαi-3 protein expression in BBMV also did not change with age. In contrast, Gβ expression and the amount of Gβ that coimmunoprecipitated with NHE3 in BBMV was greatest in 2-wk-old rats and decreased with age. Gβ common antibodies did not affect D1-like agonist inhibition of NHE activity in adult rats (8%) but markedly increased it (48%)in 4-wk-old rats. We conclude that the decreased inhibitory effect of D1-like receptors on NHE activity in BBMV in young rats is caused, in part, by the increased expression and activity of the G protein subunit Gβ/γ. The direct regulation of NHE activity by G protein subunits may be an important step in the maturation of renal tubular ion transport.

Regulation of NHE3 activity by G protein subunits in renal brush-border membranes

2000 ◽  
Vol 278 (4) ◽  
pp. R1064-R1073 ◽  
Author(s):  
Frederick E. Albrecht ◽  
Jing Xu ◽  
Orson W. Moe ◽  
Ulrich Hopfer ◽  
William F. Simonds ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Brush Border ◽  
Second Messengers ◽  
Protein Subunit ◽  
Intact Cells ◽  
Protein Subunits ◽  
Brush Border Membranes ◽  
Renal Brush Border Membrane ◽  
Renal Brush Border

NHE3 activity is regulated by phosphorylation/dephosphorylation processes and membrane recycling in intact cells. However, the Na+/H+ exchanger (NHE) can also be regulated by G proteins independent of cytoplasmic second messengers, but the G protein subunits involved in this regulation are not known. Therefore, we studied G protein subunit regulation of NHE3 activity in renal brush-border membrane vesicles (BBMV) in a system devoid of cytoplasmic components and second messengers. Basal NHE3 activity was not regulated by Gsα or Giα, because antibodies to these G proteins by themselves were without effect. The inhibitory effect of D1-like agonists on NHE3 activity was mediated, in part, by Gsα, because it was partially reversed by anti-Gsα antibodies. Moreover, the amount of Gsα that coimmunoprecipitated with NHE3 was increased by fenoldopam in both brush-border membranes and renal proximal tubule cells. Furthermore, guanosine 5′- O-(3-thiotriphosphate) but not guanosine 5′- O-(2-thiodiphosphate), the inactive analog of GDP, increased the amount of Gsα that coimmunoprecipitated with NHE3. The α2-adrenergic agonist, UK-14304 or pertussis toxin (PTX) alone had no effect on NHE3 activity, but UK-14304 and PTX treatment attenuated the D1-like receptor-mediated NHE3 inhibition. The ability of UK-14304 to attenuate the D1-like agonist effect was not due to Giα, because the attenuation was not blocked by anti-Giα antibodies or by PTX. Anti-Gβcommon antibodies, by themselves, slightly inhibited NHE3 activity but had little effect on D1-like receptor-mediated NHE3 inhibition. However, anti-Gβcommon antibodies reversed the effects of UK-14304 and PTX on D1-like agonist-mediated NHE3 inhibition. These studies provide concrete evidence of a direct regulatory role for Gsα, independent of second messengers, in the D1-like-mediated inhibition of NHE3 activity in rat renal BBMV. In addition, β/γ dimers of heterotrimeric G proteins appear to have a stimulatory effect on NHE3 activity in BBMV.

Role of oxidative stress in defective renal dopamine D1 receptor-G protein coupling and function in old Fischer 344 rats

2006 ◽  
Vol 291 (5) ◽  
pp. F945-F951 ◽  
Author(s):  
Riham Zein Fardoun ◽  
Mohammad Asghar ◽  
Mustafa Lokhandwala
Keyword(s):  
Oxidative Stress ◽  
G Protein ◽  
D1 Receptor ◽  
Serine Phosphorylation ◽  
D1 Receptors ◽  
Adult Rats ◽  
G Protein Coupling ◽  
Protein Coupling ◽  
Age Related ◽  
Old Rats

Aging is associated with an increase in oxidative stress. Previously, we have reported that dopamine failed to inhibit proximal tubular Na-K-ATPase and to promote sodium excretion in old rats (Beheray S, Kansra V, Hussain T, and Lokhandwala MF. Kidney Int 58: 712–720, 2000). This was due to uncoupling of dopamine D1 receptors from G proteins resulting from hyperphosphorylation of D1 receptors. The present study was designed to test the role of oxidative stress in the age-related decline in renal dopamine D1 receptor function. We observed that old animals had increased malondialdehyde (MDA) levels, a biomarker of oxidative stress, and decreased D1 receptor number and protein in the proximal tubules (PT) compared with adult rats. In old rats, there was increased G protein-coupled receptor kinase-2 (GRK-2) abundance, increased basal serine phosphorylation of D1 receptors, and defective D1 receptor-G protein coupling in PT membranes. Interestingly, supplementation with an antioxidant, tempol (1 mmol/l in drinking water for 15 days), lowered MDA levels and normalized D1 receptor number and protein in old rats to the level seen in adult rats. Furthermore, tempol decreased GRK-2 abundance and D1 receptor serine phosphorylation and restored D1 receptor-G protein coupling in PT of old rats. The functional consequence of these changes was the restoration of the natriuretic response to D1 receptor activation in tempol-supplemented old rats. Therefore, in old rats, tempol reduces oxidative stress and prevents GRK-2 membranous abundance and hyperphosphorylation of D1 receptors, resulting in restoration of D1 receptor-G protein coupling and the natriuretic response to SKF-38393. Thus tempol, by lowering oxidative stress, normalizes the age-related decline in dopamine receptor function.

Effect of age on renal conservation of phosphate in the rat

1986 ◽  
Vol 251 (3) ◽  
pp. F399-F407 ◽  
Author(s):  
G. M. Kiebzak ◽  
B. Sacktor
Keyword(s):  
Age Groups ◽  
Membrane Vesicles ◽  
Fractional Excretion ◽  
Renal Handling ◽  
Pi Transport ◽  
Age Related ◽  
Renal Brush Border Membrane ◽  
Low Phosphorus ◽  
Old Rats ◽  
Effect Of Age

Renal handling of phosphate (Pi) was examined in male Wistar-derived rats, 2-3, 6, 12, 18, and 24 mo of age. We observed a significant age-related phosphaturia [i.e., elevated urinary excretion (UPi V) and fractional excretion (FEPi)] in rats fed a normal phosphorus diet (NPD; 0.5% Pi). Concomitantly, plasma Pi decreased significantly and progressively with age. The mechanism of this age-related decrement in Pi conservation was examined by determining the initial (5 s) rate of Na+ gradient-dependent uptake of Pi in renal brush-border membrane vesicles (BBMV). Pi uptake significantly declined with increasing age. No consistent age-related decrease was seen in the Na+ gradient-dependent uptakes of glucose and proline by the same BBMV preparations, demonstrating the specificity of the Pi transport decrement. Pi transport kinetics revealed a significant age-related decrease in Vmax. No difference in Km of Pi was seen between age groups. These kinetic findings suggest either a decreased number of Pi carriers or decreased turnover of Pi carriers. Elevated parathyroid hormone did not explain the alteration in Pi conservation since urinary cAMP was not elevated in the intact senescent rat, and Pi uptake was not normalized in 24-mo-old rats 3 days after parathyroidectomy. The senescent 24-mo-old rat as well as the young adult 6-mo-old animal adapted to a low-phosphorus diet (LPD; 0.1% Pi) with a striking (greater than 100%) increase in Pi uptake by BBMV compared with NPD. thus the senescent kidney retained the capacity to respond appropriately to a LPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine inhibits Na(+)-H+ exchanger activity in renal BBMV by stimulation of adenylate cyclase

1990 ◽  
Vol 259 (2) ◽  
pp. F297-F303 ◽  
Author(s):  
C. C. Felder ◽  
T. Campbell ◽  
F. Albrecht ◽  
P. A. Jose
Keyword(s):  
Adenylate Cyclase ◽  
Binding Sites ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Inhibitory Effect ◽  
Ion Binding ◽  
Natriuretic Effect ◽  
Ion Binding Sites ◽  
Renal Tubular ◽  
Exchange Activity

To determine a renal tubular mechanism for the natriuretic effect of dopamine (DA) and DA-1 agonists, we measured Na(+)-H+ exchange activity (amiloride sensitive) in rat renal cortical brush-border membrane vesicles (BBMV). Renal cortical tissues were preincubated with ligands before BBMV preparation to study Na(+)-H+ exchange activity in the absence of the added ligands that may compete for ion binding sites of the exchanger. DA and DA-1 agonist-inhibited Na(+)-H+ exchange activity was concentration and time dependent. The inhibitory effect was not due to increased permeability, collapse of the proton gradient, or change in vesicle size and did not extend to Na(+)-glucose symport. DA-2 agonists had no effect, whereas alpha-adrenergic agonists increased Na(+)-H+ exchange activity. Kinetic analysis revealed that the DA-1 agonist inhibited Na(+)-H+ exchange activity by a noncompetitive process. 2',5'-Dideoxyadenosine inhibited adenylate cyclase activity and reversed the inhibitory effect of DA-1 agonist on the exchanger. H4, an isoquinoline sulfonamide, which inhibits protein kinase A, also reversed the inhibitory effect of DA-1 agonist on the exchanger. Thus the DA-1 agonist-mediated inhibition of Na(+)-H+ exchange activity in BBMV is a receptor-mediated adenylate cyclase-linked process.

Ontogeny of DA1 receptor-mediated natriuresis in the rat: in vivo and in vitro correlations

1992 ◽  
Vol 263 (3) ◽  
pp. R631-R638 ◽  
Author(s):  
S. Kaneko ◽  
F. Albrecht ◽  
L. D. Asico ◽  
G. M. Eisner ◽  
J. E. Robillard ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Receptor Subtypes ◽  
Renal Brush Border Membrane ◽  
Natriuretic Effect ◽  
Old Rats ◽  
22Na Uptake

The natriuretic and diuretic effects of dopamine are attenuated in the young. Because dopamine has actions on receptors (e.g., adrenergic, serotonin) other than dopamine, we studied a novel dopamine agonist, pramipexole, which has a selectivity to both DA1 and DA2-receptor subtypes. Intravenous administration of pramipexole resulted in a dose-related (1, 10, and 100 micrograms.kg-1.min-1) increase in urine flow and absolute and fractional sodium excretion and a decrease in mean arterial pressure (MAP) in three groups of rats studied. Pramipexole induced a greater decrease in MAP in 6- to 7- (n = 5) and 9- to 16- (n = 6) than in 3- to 4-wk-old (n = 8) rats; the natriuresis and diuresis were greatest in 12- to 16- and least in 3- to 4-wk-old rats. The renal effects of pramipexole were mainly due to actions at the DA1 receptor, since these effects were completely blocked by the coinfusion of a DA1 antagonist, SKF 83742. To explore further a cause of the attenuated natriuretic effect of pramipexole in the young, we studied the effect of a selective DA1-receptor agonist, fenoldopam, on amiloride-sensitive 22Na+ uptake in renal brush-border membrane vesicles. The 3-s amiloride-sensitive uptake was inhibited (45%) by fenoldopam (5 x 10(-5)M) in 9- to 16- (n = 6) but not in 3- to 4-wk-old (n = 5) rats. These studies suggest that the attenuated natriuretic effect of dopamine in the young is in part due to decreased DA1 action on the brush-border membrane Na(+)-H+ exchanger.

Sodium-phosphate transporter adaptation to dietary phosphate deprivation in normal and hypophosphatemic mice

1995 ◽  
Vol 268 (6) ◽  
pp. G917-G924 ◽  
Author(s):  
J. F. Collins ◽  
N. Bulus ◽  
F. K. Ghishan
Keyword(s):  
Brush Border ◽  
Molecular Mechanisms ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Fold Increase ◽  
Xenopus Laevis Oocytes ◽  
Protein Levels ◽  
Renal Brush Border Membrane ◽  
Renal Tubular Reabsorption ◽  
Renal Tubular

The X-linked hypophosphatemic (Hyp) mouse is a model for hypophosphatemic vitamin D-resistant rickets and is a homologue of human X-linked hypophosphatemia. The defect in the Hyp mouse appears to be related to decreased renal tubular reabsorption of P(i) via the renal brush-border membrane (Na(+)-P(i)) transporter. Dietary P(i) deprivation upregulates Na(+)-P(i) transport activity in brush-border membrane vesicles (BBMV) isolated from both normal and Hyp mice; however, the molecular mechanisms underlying this phenomenon are not known. The current studies were designed to investigate the effect of P(i) deprivation on the renal Na(+)-P(i) transporter. Low P(i) diet upregulated Na(+)-P(i) transporter activity in isolated BBMV by 2.1-fold in normal and Hyp mice (n = 3, P = 0.01). Low P(i) diet also induced a 1.9 +/- 0.3-fold increase in normal mice and 2.9 +/- 0.4-fold increase in Hyp mice in Na(+)-P(i) transporter message levels (n = 3, P = 0.028). The increase in message level encoding the Na(+)-P(i) transporter stimulated increased Na(+)-dependent P(i) uptake by Xenopus laevis oocytes when poly(A)+ RNA was injected into them from mice on low P(i) diet (approximately 1.67-fold in normal mice and 1.33-fold in Hyp mice). Immunoreactive protein levels increased 2.3 +/- 0.4-fold in normal mice and 8.2 +/- 0.5 in the Hyp mouse kidney cortexes (n = 3, P = 0.0001) in response to dietary P(i) deprivation.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of G-protein-coupled receptor signalling and desensitization

2004 ◽  
Vol 32 (6) ◽  
pp. 1029-1031 ◽  
Author(s):  
C. Krasel ◽  
J.-P. Vilardaga ◽  
M. Bünemann ◽  
M.J. Lohse
Keyword(s):  
G Protein ◽  
Second Messengers ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Receptor Activation ◽  
G Protein Coupled Receptor ◽  
Protein Subunit ◽  
Protein Activation ◽  
G Protein Coupled ◽  
Kinetics Of

The kinetics of G-protein-coupled receptor activation and deactivation has, so far, been measured only indirectly, most frequently by assessing the production of various second messengers. We have developed methods based on fluorescence resonance energy transfer to quantify the kinetics of receptor activation by agonist (measured as conformational change in the receptor), the kinetics of G-protein activation (measured as G-protein subunit rearrangement) and the kinetics of receptor inactivation by arrestins (measured as receptor–arrestin interaction). Using these methods, we show that receptor activation by agonists and signalling to G-proteins occur on the subsecond time scale, whereas receptor desensitization is limited by receptor phosphorylation and proceeds more slowly.

Adenosine A2A receptors mediate GABAergic inhibition of respiration in immature rats

2006 ◽  
Vol 100 (1) ◽  
pp. 91-97 ◽  
Author(s):  
Catherine A. Mayer ◽  
Musa A. Haxhiu ◽  
Richard J. Martin ◽  
Christopher G. Wilson
Keyword(s):  
Receptor Activation ◽  
Inhibitory Effect ◽  
Respiratory Drive ◽  
Adult Rats ◽  
A2a Receptors ◽  
Cgs 21680 ◽  
Old Rats ◽  
Apnea Of Prematurity ◽  
Adenosine A2a ◽  
The Relationship

Adenosine is a known inhibitor of respiratory output during early life. In this study we investigated the developmental changes in adenosine A2A-receptor activation on respiratory timing, as well as the relationship between adenosine and GABA. The specific adenosine A2A-receptor agonist CGS-21680 (CGS) or vehicle control was injected into the fourth ventricle of 14-day ( n = 9), 21-day ( n = 9), and adult ( n = 5) urethane-anesthetized rats while diaphragm electromyogram was monitored as an index of respiratory neural output. CGS injection resulted in a decrease in frequency and/or apnea in all 14-day-old rats and in 66% of 21-day-old rats. There was no effect of CGS injection on respiratory timing in adult rats. Prior injection of the GABAA-receptor blocker bicuculline at 14 and 21 days eliminated the CGS-induced decrease in frequency and apnea. We conclude from these studies that the inhibitory effect of A2A-receptor activation on respiratory drive is age dependent and is mediated via GABAergic inputs to the inspiratory timing neural circuitry. These findings demonstrate an important mechanism by which xanthine therapy alleviates apnea of prematurity.

Ceramide and sphingosine have an antagonistic effect on the plasma-membrane Ca2+-ATPase from human erythrocytes

2002 ◽  
Vol 362 (2) ◽  
pp. 247-251 ◽  
Author(s):  
Claudia COLINA ◽  
Vincenza CERVINO ◽  
Gustavo BENAIM
Keyword(s):  
Plasma Membrane ◽  
Second Messengers ◽  
Membrane Vesicles ◽  
Inhibitory Effect ◽  
Antagonistic Effect ◽  
Dependent Manner ◽  
Plasma Membrane Vesicles ◽  
Key Enzyme ◽  
Hydroxy Groups ◽  
Dose Dependent

The plasma-membrane Ca2+-ATPase is a key enzyme in the regulation of the intracellular Ca2+ concentration. On the other hand, sphingolipids have been recognized recently as important second messengers, acting in many systems in combination with Ca2+. In view of the fact that the Ca2+-ATPase is stimulated by ethanol, and since sphingolipids possess free hydroxy groups, we decided to study the possible effect of ceramide and sphingosine on this calcium pump. Here we show that ceramide stimulates the Ca2+-ATPase in a dose-dependent manner and additively to the activation observed in the presence of calmodulin or ethanol, when compared with any of these effectors added alone. Ceramide affects both the affinity for Ca2+ and the Vmax of the enzyme. Furthermore, this second messenger also stimulates Ca2+ transport in inside—out plasma-membrane vesicles from erythro cytes. Conversely, sphingosine, which is reported to act in many systems antagonistically with ceramide, showed an inhibitory effect on Ca2+-ATPase activity. This inhibition was also observed on the calmodulin-stimulated enzyme. These results, taken together, suggest that ceramide and sphingosine act antagonistically on the plasma-membrane Ca2+-ATPase. This is in accordance with the frequently reported opposite effect of these sphingolipids on intracellular Ca2+ concentration.

X-linked hypophosphatemic Gy mice: renal tubular maximum for phosphate vs. brush-border transport after low-P diet

1994 ◽  
Vol 266 (2) ◽  
pp. F309-F315 ◽  
Author(s):  
S. W. Thornton ◽  
H. S. Tenenhouse ◽  
J. Martel ◽  
R. W. Bockian ◽  
M. H. Meyer ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Control Diet ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Phosphate Deprivation ◽  
Renal Brush Border Membrane ◽  
Glomerular Filtrate ◽  
Renal Tubular Reabsorption ◽  
Renal Tubular

We examined the effect of the X-linked hypophosphatemic Gy mutation on the maximal renal tubular reabsorption of phosphate (TmP) and compared the effects of phosphate deprivation on both TmP and Na(+)-dependent phosphate transport in renal brush-border membrane vesicles (BBMV). Adult female normal and Gy mice were fed a control (1.0% P) or low-phosphate (0.03% P) diet for 5 days. For TmP measurement, anesthetized mice were infused intravenously with [3H]inulin and increasing increments of phosphate (0, 0.27, 0.54, and 1.08 mumol/min). TmP was significantly reduced in Gy mice on the control diet. Normal mice responded to the low-phosphate diet by raising their TmP [2.35 +/- 0.12 (n = 9) vs. 3.71 +/- 0.16 (n = 9) mumol/ml glomerular filtrate, mean +/- SE, P < 0.001], whereas in Gy mice, the change was not significant [1.46 +/- 0.10 (n = 10) vs. 1.70 +/- 0.11 (n = 10)]. In contrast, Gy mice did respond to phosphate restriction by increasing the initial-rate Na(+)-dependent phosphate transport in the renal BBMV [314 +/- 11 (n = 5) vs. 1,105 +/- 157 (n = 5) pmol.mg protein-1.6 s-1, P < 0.01] as did normal mice [583 +/- 64 (n = 5) vs. 1,692 +/- 203 (n = 5) pmol.mg protein-1.6 s-1, P < 0.01]. In conclusion, the adaptive increase in Na(+)-phosphate cotransport in the brush-border membrane of the proximal tubule is not sufficient for the overall increase in TmP in the whole kidney in response to dietary phosphate deprivation.

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