Effects of endothelin on rat renal proximal tubule Na(+)-Pi cotransport and Na+/H+ exchange

Endothelin (ET), a powerful vasoconstrictive peptide, is distributed ubiquitously in various organs, including the vascular endothelium and tubules of the kidney. Although localized more abundantly to the glomerulus and inner medullary collecting duct, ET receptors have been identified in the proximal tubule. The possible effects of ET on proximal tubule transport and the potential role of second messengers in this process have not been described fully. To define the role of ET in proximal tubule transport, renal cortical slices were incubated for 3 min in the presence of various concentrations of ET. Incubation with low concentrations of ET-1 (1 x 10(-9) to 1 x 10(-11) M) within the physiological range stimulated both Na(+)-Pi cotransport and Na+/H+ exchange. Pretreatment with staurosporine (0.6 microM) for 25 min abolished completely the ET-induced effects on Na(+)-Pi cotransport and Na+/H+ exchange. Similarly, preincubation with phorbol ester 12-O-tetradecanoylphorbol-13-acetate (200 nM) also abolished the effects of ET on these transporters. Incubation with ET decreased significantly intracellular adenosine 3',5'-cyclic monophosphate (cAMP). Intravenous administration of pertussis toxin for 2 days prevented the ET-induced decrease in cAMP and abolished the stimulatory effects of ET on Na(+)-Pi cotransport and Na+/H+ exchange. These findings provide indirect evidence that ET participates in the regulation of proximal tubular Pi and bicarbonate homeostasis. These effects of ET are mediated by activation of protein kinase C and cAMP-dependent protein kinase A.

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Ca2+ Microdomains, Calcineurin and the Regulation of Gene Transcription

Cells ◽

10.3390/cells10040875 ◽

2021 ◽

Vol 10 (4) ◽

pp. 875

Author(s):

Gerald Thiel ◽

Tobias Schmidt ◽

Oliver G. Rössler

Keyword(s):

Transcription Factors ◽

Protein Kinase ◽

Protein Kinases ◽

Gene Transcription ◽

Intracellular Signaling ◽

Second Messengers ◽

Major Function ◽

Surface Receptors ◽

Dependent Protein

Ca2+ ions function as second messengers regulating many intracellular events, including neurotransmitter release, exocytosis, muscle contraction, metabolism and gene transcription. Cells of a multicellular organism express a variety of cell-surface receptors and channels that trigger an increase of the intracellular Ca2+ concentration upon stimulation. The elevated Ca2+ concentration is not uniformly distributed within the cytoplasm but is organized in subcellular microdomains with high and low concentrations of Ca2+ at different locations in the cell. Ca2+ ions are stored and released by intracellular organelles that change the concentration and distribution of Ca2+ ions. A major function of the rise in intracellular Ca2+ is the change of the genetic expression pattern of the cell via the activation of Ca2+-responsive transcription factors. It has been proposed that Ca2+-responsive transcription factors are differently affected by a rise in cytoplasmic versus nuclear Ca2+. Moreover, it has been suggested that the mode of entry determines whether an influx of Ca2+ leads to the stimulation of gene transcription. A rise in cytoplasmic Ca2+ induces an intracellular signaling cascade, involving the activation of the Ca2+/calmodulin-dependent protein phosphatase calcineurin and various protein kinases (protein kinase C, extracellular signal-regulated protein kinase, Ca2+/calmodulin-dependent protein kinases). In this review article, we discuss the concept of gene regulation via elevated Ca2+ concentration in the cytoplasm and the nucleus, the role of Ca2+ entry and the role of enzymes as signal transducers. We give particular emphasis to the regulation of gene transcription by calcineurin, linking protein dephosphorylation with Ca2+ signaling and gene expression.

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Erythropoietin and testicular steroidogenesis: the role of second messengers

Acta Endocrinologica ◽

10.1530/eje.0.1320103 ◽

1995 ◽

Vol 132 (1) ◽

pp. 103-108 ◽

Cited By ~ 22

Author(s):

Carlo Foresta ◽

Roberto Mioni ◽

Paola Bordon ◽

Francesco Gottardello ◽

Andrea Nogara ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Leydig Cells ◽

Second Messengers ◽

Indirect Evidence ◽

Calcium Flux ◽

Dependent Manner ◽

Kinase C ◽

Testicular Steroidogenesis

Foresta C, Mioni R, Bordon P, Gottardello F, Nogara A, Rossato M. Erythropoietin and testicular steroidogenesis: the role of second messengers. Eur J Endocrinol 1995;132:103–8. ISSN 0804–4643 It has been demonstrated that erythropoietin (EPO) influences rat and human Leydig cell steroidogenesis, stimulating testosterone production through a direct and specific receptor-mediated mechanism. The aim of this study was to investigate the mechanism by which recombinant human erythropoietin (rHuEPO) exerts its stimulatory effect on rat Leydig cells. Recombinant human EPO did not induce, at any dose tested (10−10 to 10−13 mol/l), an increase in either cAMP or cGMP, suggesting that in Leydig cells the effect of rHuEPO does not involve the adenylate or guanylate–cyclase systems. The role of transmembrane calcium flux in rHuEPO-stimulated steroidogenesis was studied by evaluating the effect of calcium channel blocker, verapamil, and by the 45Ca2+ uptake method. Verapamil did not influence rHuEPO-induced testosterone secretion and rHuEPO did not modify calcium recycling, indicating that calcium transmembrane flux is not involved in the rHuEPO effect. The protein kinase C inhibitor staurosporine (10, 30, 100 and 300 nmol/l) inhibited rHuEPO-stimulated testicular steroidogenesis in a dose-dependent manner. This indirect evidence suggests that the stimulatory effect of rHuEPO on rat Leydig cells may involve protein kinase C activation. Carlo Foresta, Institute of Internal Medicine, Via Ospedale Civile 105, 35128 Padova, Italy

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Molecular mechanisms of ANP inhibition of renal sodium transport

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y91-230 ◽

1991 ◽

Vol 69 (10) ◽

pp. 1546-1552 ◽

Cited By ~ 14

Author(s):

Bruce A. Stanton

Keyword(s):

Protein Kinase ◽

Cyclic Gmp ◽

Collecting Duct ◽

Cation Channel ◽

Sodium Reabsorption ◽

Open Probability ◽

Dependent Protein Kinase ◽

Inner Medullary Collecting Duct ◽

Dependent Protein ◽

Medullary Collecting Duct

ANP, a hormone secreted by the atria of mammalian hearts in response to volume expansion, increases urinary sodium excretion in part by inhibiting sodium reabsorption across the inner medullary collecting duct. A number of nephron segments may contribute to the ANP-induced natriuresis; however, this review will focus on the cellular mechanisms of ANP inhibition of electrogenic sodium reabsorption by the inner medullary collecting duct. Patch-clamp studies conducted on rat inner medullary collecting duct cells in primary culture revealed that ANP, via its second messenger cGMP, inhibits electrogenic sodium reabsorption by reducing the open probability of a cation channel located in the apical membrane. Cyclic GMP inhibits the cation channel and thereby sodium reabsorption by two mechanisms. First, cGMP inhibits the channel by a phosporylation-independent mechanism, by binding either to an allosteric modifier site on the channel or to a regulatory subunit. Second, cGMP inhibits the channel by activating cGMP-dependent protein kinase, which by a sequential pathway involving the GTP-binding protein, Gi inhibits the channel. These cGMP-dependent mechanisms inhibiting sodium reabsorption across the inner medullary collecting duct account for a substantial component of the natriuresis following a rise in ANP levels.Key words: inner medullary collecting duct, G proteins, cyclic GMP-dependent protein kinase, 3′,5′-cyclic GMP, signal transduction, papillary collecting duct.

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Use of LC-MS/MS and Bayes' theorem to identify protein kinases that phosphorylate aquaporin-2 at Ser256

AJP Cell Physiology ◽

10.1152/ajpcell.00377.2012 ◽

2014 ◽

Vol 307 (2) ◽

pp. C123-C139 ◽

Cited By ~ 26

Author(s):

Davis Bradford ◽

Viswanathan Raghuram ◽

Justin L. L. Wilson ◽

Chung-Lin Chou ◽

Jason D. Hoffert ◽

...

Keyword(s):

Experimental Data ◽

Protein Kinase ◽

Protein Kinases ◽

Water Transport ◽

Collecting Duct ◽

Bayes Theorem ◽

Dependent Protein Kinase ◽

Dependent Protein ◽

Medullary Collecting Duct

In the renal collecting duct, binding of AVP to the V2 receptor triggers signaling changes that regulate osmotic water transport. Short-term regulation of water transport is dependent on vasopressin-induced phosphorylation of aquaporin-2 (AQP2) at Ser256. The protein kinase that phosphorylates this site is not known. We use Bayes' theorem to rank all 521 rat protein kinases with regard to the likelihood of a role in Ser256 phosphorylation on the basis of prior data and new experimental data. First, prior probabilities were estimated from previous transcriptomic and proteomic profiling data, kinase substrate specificity data, and evidence for kinase regulation by vasopressin. This ranking was updated using new experimental data describing the effects of several small-molecule kinase inhibitors with known inhibitory spectra (H-89, KN-62, KN-93, and GSK-650394) on AQP2 phosphorylation at Ser256 in inner medullary collecting duct suspensions. The top-ranked kinase was Ca2+/calmodulin-dependent protein kinase II (CAMK2), followed by protein kinase A (PKA) and protein kinase B (AKT). Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based in vitro phosphorylation studies compared the ability of three highly ranked kinases to phosphorylate AQP2 and other inner medullary collecting duct proteins, PKA, CAMK2, and serum/glucocorticoid-regulated kinase (SGK). All three proved capable of phosphorylating AQP2 at Ser256, although CAMK2 and PKA were more potent than SGK. The in vitro phosphorylation experiments also identified candidate protein kinases for several additional phosphoproteins with likely roles in collecting duct regulation, including Nedd4-2, Map4k4, and 3-phosphoinositide-dependent protein kinase 1. We conclude that Bayes' theorem is an effective means of integrating data from multiple data sets in physiology.

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