NFAT regulates calcium-sensing receptor-mediated TNF production

2006 ◽  
Vol 290 (5) ◽  
pp. F1110-F1117 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
Shoujin Hao ◽  
Karin D. Rodland ◽  
John C. McGiff ◽  
...  
Keyword(s):  
Extracellular Fluid ◽  
Dominant Negative ◽  
Peptide Ligand ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Dependent Activity ◽  
Calcineurin Activity

Because nuclear factor of activated T cells (NFAT) has been implicated in TNF production as well as osmoregulation and salt and water homeostasis, we addressed whether calcium-sensing receptor (CaR)-mediated TNF production in medullary thick ascending limb (mTAL) cells was NFAT dependent. TNF production in response to addition of extracellular Ca2+ (1.2 mM) was abolished in mTAL cells transiently transfected with a dominant-negative CaR construct (R796W) or pretreated with the phosphatidylinositol phospholipase C (PI-PLC) inhibitor U-73122. Cyclosporine A (CsA), an inhibitor of the serine/threonine phosphatase calcineurin, and a peptide ligand, VIVIT, that selectively inhibits calcineurin-NFAT signaling, also prevented CaR-mediated TNF production. Increases in calcineurin activity in cells challenged with Ca2+ were inhibited after pretreatment with U-73122 and CsA, suggesting that CaR activation increases calcineurin activity in a PI-PLC-dependent manner. Moreover, U-73122, CsA, and VIVIT inhibited CaR-dependent activity of an NFAT construct that drives expression of firefly luciferase in transiently transfected mTAL cells. Collectively, these data verify the role of calcineurin and NFAT in CaR-mediated TNF production by mTAL cells. Activation of the CaR also increased the binding of NFAT to a consensus oligonucleotide, an effect that was blocked by U-73122 and CsA, suggesting that a calcineurin- and NFAT-dependent pathway increases TNF production in mTAL cells. This mechanism likely regulates TNF gene transcription as U-73122, CsA, and VIVIT blocked CaR-dependent activity of a TNF promoter construct. Elucidating CaR-mediated signaling pathways that regulate TNF production in the mTAL will be crucial to understanding mechanisms that regulate extracellular fluid volume and salt balance.

CaR activation increases TNF production by mTAL cells via a Gi-dependent mechanism

2008 ◽  
Vol 294 (2) ◽  
pp. F345-F354 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
John C. McGiff ◽  
Nicholas R. Ferreri
Keyword(s):  
Extracellular Fluid ◽  
Inhibitory Effect ◽  
Dominant Negative ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Promoter Construct ◽  
Gf 109203X ◽  
20 Nm

We evaluated the contribution of calcium-sensing receptor (CaR)-mediated Gi-coupled signaling to TNF production in medullary thick ascending limb (mTAL) cells. A selective Gi inhibitor, pertussis toxin (PTX), but not the inactive B-oligomer binding subunit, abolished CaR-mediated increases in TNF production. The inhibitory effect of PTX was partially reversed by using an adenylate cyclase inhibitor. CaR-mediated TNF production also was partially reversed by a cAMP analog, 8-Br-cAMP. IP1 accumulation was CaR dependent and blocked by PI-PLC; partial inhibition also was observed with PTX. CaR increased calcineurin (CaN) activity by approximately threefold, and PTX prevented CaR-mediated increases in CaN activity, an nuclear factor of activated T cells (NFAT)- cis reporter construct, and a TNF promoter construct. The interaction between Gi and PKC was determined, as we previously showed that CaR-mediated TNF production was CaN and NFAT- mediated and Gq dependent. CaR activation increased PKC activity by twofold, an effect abolished by transient transfection with a dominant negative CaR construct, R796W, or pretreatment with PTX. Inhibition with the pan-specific PKC inhibitor GF 109203X (20 nM) abolished CaR-mediated increases in activity of CaN, an NFAT reporter, and a TNF promoter construct. Collectively, the data suggest that Gi-coupled signaling contributes to NFAT-mediated TNF production in a CaN- and PKC-dependent manner and may be part of a CaR mechanism to regulate mTAL function. Moreover, concurrent Gq and Gi signaling is required for CaR-mediated TNF production in mTAL cells via a CaN/NFAT pathway that is PKC dependent. Understanding CaR-mediated signaling pathways that regulate TNF production in the mTAL is crucial to defining novel mechanisms that regulate extracellular fluid volume and salt balance.

scholarly journals Calcium-sensing receptor signaling pathways in medullary thick ascending limb cells mediate COX-2-derived PGE2 production: functional significance

2008 ◽  
Vol 295 (4) ◽  
pp. F1082-F1089 ◽  
Author(s):  
Huda Ismail Abdullah ◽  
Paulina L. Pedraza ◽  
John C. McGiff ◽  
Nicholas R. Ferreri
Keyword(s):  
Ion Transport ◽  
Dominant Negative ◽  
Prostaglandin E ◽  
Thick Ascending Limb ◽  
Calcium Sensing Receptor ◽  
Activated T Cells ◽  
Calcium Sensing ◽  
Medullary Thick Ascending Limb ◽  
Cox 2

We determined the functional implications of calcium-sensing receptor (CaR)-dependent, Gq- and Gi-coupled signaling cascades, which work in a coordinated manner to regulate activity of nuclear factor of activated T cells and tumor necrosis factor (TNF)-α gene transcription that cause expression of cyclooxygenase (COX)-2-derived prostaglandin E2 (PGE2) synthesis by rat medullary thick ascending limb cells (mTAL). Interruption of Gq, Gi, protein kinase C (PKC), or calcineurin (CaN) activities abolished CaR-mediated COX-2 expression and PGE2 synthesis. We tested the hypothesis that these pathways contribute to the effects of CaR activation on ion transport in mTAL cells. Ouabain-sensitive O2 consumption, an in vitro correlate of ion transport in the mTAL, was inhibited by ∼70% in cells treated for 6 h with extracellular Ca2+ (1.2 mM), an effect prevented in mTAL cells transiently transfected with a dominant negative CaR overexpression construct (R796W), indicating that the effect was initiated by stimulation of the CaR. Pretreatment with the COX-2-selective inhibitor, NS-398 (1 μM), reversed CaR-activated decreases in ouabain-sensitive O2 consumption by ∼60%, but did not alter basal levels of ouabain-sensitive O2 consumption. Similarly, inhibition of either Gq, Gi, PKC, or CaN, which are components of the mechanism associated with CaR-stimulated COX-2-derived PGE2 synthesis, reversed the inhibitory effects of CaR on O2 consumption without affecting basal O2 consumption. Our findings identified signaling elements required for CaR-mediated TNF production that are integral components regulating mTAL function via a mechanism involving COX-2 expression and PGE2 production.

scholarly journals The Calcium-Sensing Receptor Increases Activity of the Renal NCC through the WNK4-SPAK Pathway

2018 ◽  
Vol 29 (7) ◽  
pp. 1838-1848 ◽  
Author(s):  
Silvana Bazúa-Valenti ◽  
Lorena Rojas-Vega ◽  
María Castañeda-Bueno ◽  
Jonatan Barrera-Chimal ◽  
Rocío Bautista ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Oral Administration ◽  
Apical Membrane ◽  
Hek293 Cells ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing

Background Hypercalciuria can result from activation of the basolateral calcium-sensing receptor (CaSR), which in the thick ascending limb of Henle’s loop controls Ca2+ excretion and NaCl reabsorption in response to extracellular Ca2+. However, the function of CaSR in the regulation of NaCl reabsorption in the distal convoluted tubule (DCT) is unknown. We hypothesized that CaSR in this location is involved in activating the thiazide-sensitive NaCl cotransporter (NCC) to prevent NaCl loss.Methods We used a combination of in vitro and in vivo models to examine the effects of CaSR on NCC activity. Because the KLHL3-WNK4-SPAK pathway is involved in regulating NaCl reabsorption in the DCT, we assessed the involvement of this pathway as well.Results Thiazide-sensitive 22Na+ uptake assays in Xenopus laevis oocytes revealed that NCC activity increased in a WNK4-dependent manner upon activation of CaSR with Gd3+. In HEK293 cells, treatment with the calcimimetic R-568 stimulated SPAK phosphorylation only in the presence of WNK4. The WNK4 inhibitor WNK463 also prevented this effect. Furthermore, CaSR activation in HEK293 cells led to phosphorylation of KLHL3 and WNK4 and increased WNK4 abundance and activity. Finally, acute oral administration of R-568 in mice led to the phosphorylation of NCC.Conclusions Activation of CaSR can increase NCC activity via the WNK4-SPAK pathway. It is possible that activation of CaSR by Ca2+ in the apical membrane of the DCT increases NaCl reabsorption by NCC, with the consequent, well known decrease of Ca2+ reabsorption, further promoting hypercalciuria.

scholarly journals Calcium-Sensing Receptor Stimulation in Cultured Glomerular Podocytes Induces TRPC6-Dependent Calcium Entry and RhoA Activation

2017 ◽  
Vol 43 (5) ◽  
pp. 1777-1789 ◽  
Author(s):  
Lei Zhang ◽  
Tianrong Ji ◽  
Qin Wang ◽  
Kexin Meng ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Protective Action ◽  
Focal Adhesions ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Rhoa Activity ◽  
Rhoa Activation ◽  
Calcium Sensing

Background/Aims: Recent studies provided compelling evidence that stimulation of the calcium sensing receptor (CaSR) exerts direct renoprotective action at the glomerular podocyte level. This protective action may be attributed to the RhoA-dependent stabilization of the actin cytoskeleton. However, the underlying mechanisms remain unclear. Methods: In the present study, an immortalized human podocyte cell line was used. Fluo-3 fluorescence was utilized to determine intracellular Ca2+ concentration ([Ca2+]i), and western blotting was used to measure canonical transient receptor potential 6 (TRPC6) protein expression and RhoA activity. Stress fibers were detected by FITC-phalloidin. Results: Activating CaSR with a high extracellular Ca2+ concentration ([Ca2+]o) or R-568 (a type II CaSR agonist) induces an increase in the [Ca2+]i in a dose-dependent manner. This increase in [Ca2+]i is phospholipase C (PLC)-dependent and is smaller in the absence of extracellular Ca2+ than in the presence of 0.5 mM [Ca2+]o. The CaSR activation-induced [Ca2+]i increase is attenuated by the pharmacological blockage of TRPC6 channels or siRNA targeting TRPC6. These data suggest that TRPC6 is involved in CaSR activation-induced Ca2+ influx. Consistent with a previous study, CaSR stimulation results in an increase in RhoA activity. However, the knockdown of TRPC6 significantly abolished the RhoA activity increase induced by CaSR stimulation, suggesting that TRPC6-dependent Ca2+ entry is required for RhoA activation. The activated RhoA is involved in the formation of stress fibers and focal adhesions in response to CaSR stimulation because siRNA targeting RhoA attenuated the increase in the stress fiber mediated by CaSR stimulation. Moreover, this effect of CaSR activation on the formation of stress fibers is also abolished by the knockdown of TRPC6. Conclusion: TRPC6 is involved in the regulation of stress fiber formation and focal adhesions via the RhoA pathway in response to CaSR activation. This may explain the direct protective action of CaSR agonists.

Type-5 Bartter syndrome presenting with metabolic seizure in adulthood

2021 ◽  
Vol 14 (2) ◽  
pp. e235349
Author(s):  
Aqeel Hussain ◽  
Mahendra Atlani ◽  
Abhishek Goyal ◽  
Alkesh Kumar Khurana
Keyword(s):  
Age Of Onset ◽  
Bartter Syndrome ◽  
Electrolyte Imbalance ◽  
Thick Ascending Limb ◽  
Calcium Sensing Receptor ◽  
Inherited Disorders ◽  
Calcium Sensing ◽  
Aged Woman ◽  
Middle Aged Woman ◽  
Renal Tubular

Bartter syndrome is a very rare and heterogeneous disease with variable age of onset and symptom severity. Genotypically they have inherited disorders of the thick ascending limb in the renal tubular system, which manifest phenotypically as electrolyte imbalance due to loss of sodium, chloride and potassium. Gain of function mutations in the calcium-sensing receptor has been described in some patients with Bartter’s syndrome (type-5 Bartter syndrome or autosomal dominant hypocalcaemia with Bartter syndrome) associated with hypocalcaemia and hypercalciuria differentiating it from Gitelman syndrome. This phenotype has been reported to present in adulthood with metabolic abnormalities. We present a case of a middle-aged woman who presented with metabolic seizures and on evaluation was found to have profound electrolyte abnormalities which were corrected with supplements and led to the resolution of symptoms.

Thick ascending limb claudins are altered to increase calciuria and magnesiuria in metabolic acidosis

2021 ◽  
Author(s):  
Il Hwan Oh ◽  
Chor Ho Jo ◽  
Sua Kim ◽  
Sungsin Jo ◽  
Sungjin Chung ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Immunofluorescence Microscopy ◽  
Urinary Calcium ◽  
Receptor Protein ◽  
Thick Ascending Limb ◽  
Sprague Dawley ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Sprague Dawley Rats ◽  
Calcium And Magnesium

Urinary calcium and magnesium wasting is a characteristic feature of metabolic acidosis, and this study focused on the role of the thick ascending limb of Henle's loop in metabolic acidosis-induced hypercalciuria and hypermagnesiuria because thick ascending limb is an important site of paracellular calcium and magnesium reabsorption. Male Sprague-Dawley rats were used to determine the effects of acid loading (by adding NH4Cl 7.2 mmol/220 g BW/d to food slurry for 7 days) on renal expression of claudins and then to evaluate whether the results were reversed by antagonizing calcium-sensing receptor (using NPS-2143). At the end of each animal experiment, the kidneys were harvested for immunoblotting, immunofluorescence microscopy and qPCR analysis of claudins and the calcium-sensing receptor. As expected, NH4Cl loading lowered urinary pH and increased excretion of urinary calcium and magnesium. In NH4Cl-loaded rats, renal protein and mRNA expression of claudin-16, and claudin-19 decreased compared with controls. However, claudin-14 protein and mRNA increased in NH4Cl-loaded rats. Consistently, the calcium-sensing receptor protein and mRNA were upregulated in NH4Cl-loaded rats. All these changes were reversed by NPS-2143 coadministration and were confirmed using immunofluorescence microscopy. Hypercalciuria and hypermagnesiuria in NH4Cl-loaded rats were significantly ameliorated by NPS-2143 coadministration as well. We conclude that in metabolic acidosis, claudin-16 and claudin-19 in the thick ascending limb are downregulated to produce hypercalciuria and hypermagnesiuria via the calcium-sensing receptor.

Hypercalcaemia

2011 ◽  
pp. 642-652
Author(s):  
Ronen Levi ◽  
Justin Silver
Keyword(s):  
Extracellular Fluid ◽  
Immune Functions ◽  
Calcium Sensing Receptor ◽  
Neuromuscular Activation ◽  
Plasma Coagulation ◽  
Dihydroxyvitamin D ◽  
1,25 Dihydroxyvitamin D ◽  
Calcium Sensing ◽  
Life Threatening

Ionized calcium is essential for several physiological functions, including neuromuscular activation, endocrine and exocrine secretions, integrity of cellular bilayers, plasma coagulation, immune functions and bone metabolism. Extracellular fluid (ECF) calcium is uniquely controlled by its own calcium-sensing receptor, regulating the secretion of parathyroid hormone (PTH), synthesis of 1,25-dihydroxyvitamin D, and the renal reabsorption of filtered calcium (see Chapter 4.1). With the advent of the autoanalyser and routine determination of serum calcium levels, recognition of hypercalcaemia has become common. However, the clinical spectrum of hypercalcaemia varies from a laboratory-detected, asymptomatic mineral disorder to a life-threatening state.

scholarly journals A novel mutation in the calcium-sensing receptor in a French family with familial hypocalciuric hypercalcaemia

2011 ◽  
Vol 165 (2) ◽  
pp. 359-363 ◽  
Author(s):  
Abdallah Al-Salameh ◽  
Filomena Cetani ◽  
Elena Pardi ◽  
Carmen Vulpoi ◽  
Peggy Pierre ◽  
...  
Keyword(s):  
Inositol Phosphates ◽  
Novel Mutation ◽  
Dominant Negative ◽  
Calcium Handling ◽  
Dominant Negative Effect ◽  
Base Substitution ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Extensive Evaluation ◽  
Negative Effect

ObjectiveThe calcium-sensing receptor (CASR) has an important role in calcium homoeostasis by controlling PTH secretion and renal calcium handling. Inactivating mutations in the CASR gene (HGNC ID: 1514) cause familial hypocalciuric hypercalcaemia (FHH). We present a case of FHH patient to describe a novel mutation in the CASR.Subjects and methodsA 34-year-old patient was referred because of recurrent hypercalcaemia after resection of two hyperplastic parathyroids. Extensive evaluation found elevated PTH and low calcium/creatinine clearance ratio. One of her three children had high serum calcium concentrations. Genetic studies were performed by PCR amplification of CASR coding exons and direct sequencing of PCR products. Transient transfection of the wild-type (WT) CASR and the mutant CASR into COS-7 was performed to assess functional impact of the mutation and the capacity of either protein to mediate increases in cellular levels of inositol phosphates (IPs).ResultsCASR sequencing found a previously undescribed heterozygous base substitution, determining a change of threonine to isoleucine at codon 550 (p.T550I) in the sixth exon. In contrast to those transfected with WT CASR, which showed a five- to eightfold increase in total IPs at high levels of calcium, COS-7 cells transfected with the (p.T550I) mutant showed no increase confirming to the inactivating nature of the mutation. COS-7 cells co-transfected with the WT and the (p.T550I) mutant showed an intermediate response suggesting a possible dominant negative effect.ConclusionThis case report presents a not-yet-described mutation in the cysteine-rich region of the CASR extracellular domain, a mutation with a possible dominant negative effect.

scholarly journals Mitogenic Action of Calcium-Sensing Receptor on Rat Calvarial Osteoblasts

Endocrinology ◽  
2004 ◽  
Vol 145 (7) ◽  
pp. 3451-3462 ◽  
Author(s):  
Naibedya Chattopadhyay ◽  
Shozo Yano ◽  
Jacob Tfelt-Hansen ◽  
Paul Rooney ◽  
Deepthi Kanuparthi ◽  
...  
Keyword(s):  
Dominant Negative ◽  
Calcium Sensing Receptor ◽  
Jnk Pathway ◽  
Early Growth Response ◽  
Calcium Sensing ◽  
Mitogenic Action ◽  
Igf I ◽  
Extracellular Factor ◽  
Post Harvesting ◽  
Early Growth Response 1

Abstract The parathyroid calcium-sensing receptor (CaR) plays a nonredundant role in systemic calcium homeostasis. In bone, Ca2+o, a major extracellular factor in the bone microenvironment during bone remodeling, could potentially serve as an extracellular first messenger, acting via the CaR, that stimulates the proliferation of preosteoblasts and their differentiation to osteoblasts (OBs). Primary digests of rat calvarial OBs express the CaR as assessed by RT-PCR, Northern, and Western blot analysis, and immunocolocalization of the CaR with the OB marker cbfa-1. Real-time PCR revealed a significant increase in CaR mRNA in 5- and 7-d cultures compared with 3-d cultures post harvesting. High Ca2+o did not affect the expression of CaR mRNA during this time but up-regulated cyclin D (D1, D2, and D3) genes, which are involved in transition from the G1 to the S phase of the cell cycle, as well as the early oncogenes, c-fos and early growth response-1; high Ca2+o did not, however, alter IGF-I expression, a mitogenic factor for OBs. The high Ca2+o-dependent increase in the proliferation of OBs was attenuated after transduction with a dominant-negative CaR (R185Q), confirming that the effect of high Ca2+o is CaR mediated. Stimulation of proliferation by the CaR involves the Jun-terminal kinase (JNK) pathway, as high Ca2+o stimulated the phosphorylation of JNK in a CaR-mediated manner, and the JNK inhibitor SP600125 abolished CaR-induced proliferation. Our data, therefore, show that the parathyroid/kidney CaR expressed in rat calvarial OBs exerts a mitogenic effect that involves activation of the JNK pathway and up-regulation of several mitogenic genes.

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