Isoforms of renal Na-K-2Cl cotransporter NKCC2: expression and functional significance

Castrop, Hayo; Schnermann, Jürgen

doi:10.1152/ajprenal.00106.2008

Cited by 87 publications

(92 citation statements)

References 82 publications

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“…Similarity the slc12a1 gene encodes three Na-K-Cl cotransporter isoforms with diverse carboxyl-terminal sequences (NKCC2). These isoforms show different localizations along the thick ascending limb of the loop of Henle and affinity for NaCl (19).…”

Section: Discussionmentioning

confidence: 99%

Cystinosin-LKG rescues cystine accumulation and decreases apoptosis rate in cystinotic proximal tubular epithelial cells

et al. 2016

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Background: Nephropathic cystinosis is a lysosomal storage disease that is caused by mutations in the CTNS gene encoding a cystine/proton symporter cystinosin and an isoform cystinosin-LKG which is generated by an alternative splicing of exon 12. We have investigated the physiological role of the cystinosin-LKG that is widely expressed in epithelial tissues. Methods: We have analyzed the intracellular localization and the function of the cystinosin-LKG conjugated with DsRed (cystinosin-LKG-RFP) in Madin-Darby canine kidney cells (MDCK II) and in proximal tubular epithelial cells carrying a deletion of the CTNS gene (cystinotic PTEC), respectively. results: Cystinosin-LKG-RFP colocalized with markers of lysosomes, late endosomes and was also expressed on the apical surface of polarized MDCK II cells. Moreover, immuneelectron microscopy images of MDCK II cells overexpressing cystinosin-LKG-RFP showed stacked lamellar membranes inside perinuclear lysosomal structures. To study the role of LKG-isoform, we have investigated cystine accumulation and apoptosis that have been described in cystinotic cells. Cystinosin-LKG decreased cystine levels by approximately 10-fold similarly to cystinosin-RFP. The levels of TNFα-and actinomycin D-inducted apoptosis dropped in cystinotic cells expressing LKG-isoform. This effect was also similar to the main isoform. conclusion: Our results suggest that cystinosin-LKG and cystinosin move similar functional activities in cells.n ephropathic cystinosis (NC) is a rare lysosomal storage disease. It is caused by defective activity of cystinosin, a proton/cystine symporter that is ubiquitously expressed on lysosomal membranes, which leads to cystine accumulation into lysosomes and crystal formations in many tissues (1). One of the first symptoms of NC is renal Fanconi syndrome, secondary to a global dysfunction of proximal tubular cells. During their lifetimes, patients with NC develop several others symptoms in particular, if they are not well treated with cysteamine (2,3).Recent works have demonstrated an involvement of cystinosin in lysosomal kinetics and exocytosis (4), vesicle trafficking (4,5), autophagy, (6) and in sensing cell oxidative state (7). Studies using a cystinotic mouse model have shown decreased expression of the multi-ligand receptors megalin and cubilin in proximal tubules; this was associated with cell dedifferentiation and apoptosis (5,8). Also, enhanced cell death due to activation of proapoptotic signals probably occurs in other tissues (9-11).Cystinosin (accession number: NP_004928) is composed of seven transmembrane domains that bear two lysosomal targeting motifs (GYDQL and YFPQA) and seven N-glycosylation sites in the amino-terminal region (12). The aceview database reports various alternative splicing transcripts for the CTNS gene that encodes the cystinosin (http://www.ncbi.nlm.nih. gov/IEB/Research/Acembly). In 2008, we have identified a 400 amino acid cystinosin isoform that derives from alternative splicing of CTNS gene exon 12 (accession number: NP_001026...

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Section: Discussionmentioning

confidence: 99%

Cystinosin-LKG rescues cystine accumulation and decreases apoptosis rate in cystinotic proximal tubular epithelial cells

et al. 2016

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“…1B). These isoforms differ in their transcript levels, localisation and ion affinity properties (Castrop and Schnermann, 2008).…”

Section: Discussionmentioning

confidence: 99%

Regulation of the NKCC2 ion cotransporter by SPAK-OSR1-dependent and -independent pathways

Richardson

Sakamoto

Heros

et al. 2011

Journal of Cell Science

164

174

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Ion cotransporters, such as the Na+/Cl− cotransporter (NCC), control renal salt re-absorption and are regulated by the WNK-signalling pathway, which is over-stimulated in patients suffering from Gordon's hypertension syndrome. Here, we study the regulation of the NKCC2 (SLC12A1) ion cotransporter that contributes towards ~25% of renal salt re-absorption and is inhibited by loop-diuretic hypertensive drugs. We demonstrate that hypotonic low-chloride conditions that activate the WNK1-SPAK and OSR1 pathway promote phosphorylation of NKCC2 isoforms (A, B and F) at five residues (Ser91, Thr95, Thr100, Thr105 and Ser130). We establish that the SPAK and OSR1 kinases activated by WNK interact with an RFQV motif on NKCC2 and directly phosphorylate Thr95, Thr100, Thr105 and, possibly, Ser91. Our data indicate that a SPAK-OSR1-independent kinase, perhaps AMP-activated protein kinase (AMPK), phosphorylates Ser130 and that phosphorylation of Thr105 and Ser130 plays the most important roles in stimulating NKCC2 activity. In contrast with NCC, whose membrane translocation is triggered by SPAK-OSR1 phosphorylation, NKCC2 appears to be constitutively at the membrane. Our findings provide new insights into how NKCC2 is regulated and suggest that inhibitors of SPAK and/or OSR1 for the treatment of hypertension would be therapeutically distinct from thiazide or loop diuretics, as they would suppress the activity of both NCC and NKCC2.

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“…Recapitulating, furosemide can increase renin release by activation of the sympathetic nervous system (15,32), a decrease in afferent arterial perfusion pressure, and by direct inhibition of NKCC2 in the macula densa (27,151). In addition, macula densa neuronal NO synthase (nNOS)-mediated NO generation can stimulate renin release (18).…”

Section: Are Direct Vascular Actions Of Furosemide Important and Whatmentioning

confidence: 99%

Everything we always wanted to know about furosemide but were afraid to ask

Huang

Mees

Vos

et al. 2016

American Journal of Physiology-Renal Physiology

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Huang X, Dorhout Mees E, Vos P, Hamza S, Braam B. Everything we always wanted to know about furosemide but were afraid to ask. Am J Physiol Renal Physiol 310: F958 -F971, 2016. First published February 24, 2016 doi:10.1152/ajprenal.00476.2015.-Furosemide is a widely used, potent natriuretic drug, which inhibits the Na ϩ -K ϩ -2Cl Ϫ cotransporter (NKCC)-2 in the ascending limb of the loop of Henle applied to reduce extracellular fluid volume expansion in heart and kidney disease. Undesirable consequences of furosemide, such as worsening of kidney function and unpredictable effects on sodium balance, led to this critical evaluation of how inhibition of NKCC affects renal and cardiovascular physiology. This evaluation reveals important knowledge gaps, involving furosemide as a drug, the function of NKCC2 (and NKCC1), and renal and systemic indirect effects of NKCC inhibition. Regarding renal effects, renal blood flow and glomerular filtration rate could become compromised by activation of tubuloglomerular feedback or by renin release, particularly if renal function is already compromised. Modulation of the intrarenal renin angiotensin system, however, is ill-defined. Regarding systemic effects, vasodilation followed by nonspecific NKCC inhibition and changes in venous compliance are not well understood. Repetitive administration of furosemide induces short-term (braking phenomenon, acute diuretic resistance) and long-term (chronic diuretic resistance) adaptations, of which the mechanisms are not well known. Modulation of NKCC2 expression and activity in kidney and heart failure is ill-defined. Lastly, furosemide's effects on cutaneous sodium stores and on uric acid levels could be beneficial or detrimental. Concluding, a considerable knowledge gap is identified regarding a potent drug with a relatively specific renal target, NKCC2, and renal and systemic actions. Resolving these questions would increase the understanding of NKCCs and their actions and improve rational use of furosemide in pathophysiology of fluid volume expansion. extracellular fluid volume; natriuresis; renal function; chronic kidney disease; heart failure DIURETICS BLOCKING THE Na ϩ -K ϩ -2Cl Ϫ cotransporter (NKCC) have an important place in the treatment of fluid overload, specifically in the context of kidney disease and heart failure (64). Of the drugs that inhibit the NKCC2 in the loop of Henle (furosemide, bumetanide, torsemide, ethacrynic acid), furosemide is most commonly applied (66) and Ͼ40 million prescriptions are dispensed every year in the USA (66a). However, many uncertainties remain about intrarenal and systemic actions of furosemide, including its two main targets NKCC1 and NKCC2.Clinically, there are a number of undesirable consequences of the use of furosemide, of which the pathophysiological mechanisms have not been sufficiently investigated. Furosemide has been associated with worsening of kidney function in patients treated for volume overload admitted for acute heart failure (104) and even glomerular filtration rate (GFR) ...

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Isoforms of renal Na-K-2Cl cotransporter NKCC2: expression and functional significance

Cited by 87 publications

References 82 publications

Cystinosin-LKG rescues cystine accumulation and decreases apoptosis rate in cystinotic proximal tubular epithelial cells

Cystinosin-LKG rescues cystine accumulation and decreases apoptosis rate in cystinotic proximal tubular epithelial cells

Regulation of the NKCC2 ion cotransporter by SPAK-OSR1-dependent and -independent pathways

Everything we always wanted to know about furosemide but were afraid to ask

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