Rare mutations in SLC12A1 and SLC12A3 protect against hypertension by reducing the activity of renal salt cotransporters. (original) (raw)
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Functional Properties of NCC with Rare Independent Mutations Decreasing the Risk of Hypertension
"Screening of more than 3 thousand members of the Framingham Heart Study for variations in the renal NaCl cotransporter, NCC, revealed that subjects with rare independent mutations in one allele have a significantly lower blood pressure and are protected against hypertension (Ji et al, Nature Gen, 2008). Although some of the mutations were previously reported as cause of Gitelman’s disease, others have not been shown to be associated with this inherited disease and thus, the consequence of such mutations in NCC activity is not known. We have introduced five independent mutations in the rat NCC sequence to find out the consequences upon NCC functional properties. The analyzed mutations were L153F, S186F, A230T, F493L, and G777E. Xenopus laevis oocytes were injected with 20 ng ofwild type or mutants NCC cRNA and three days later the basal activity and response to regulators was assessed by measuring the thiazide-sensitive 22Na+ Uptake. To assess the effect of modulators, oocytes were co-injected with WNK3 or WNK4 cRNA, or were exposed to intracellular chloride depletion maneuvers (ICD) known to activate NCC (Pacheco-Alvarez et al, JBC 2006). The activity of wild type NCC was taken as 100% and data from all groups was normalized accordingly. The basal NCC activity was significantly reduced in four out of the five mutants NCCs. The percentage of activity was 60 %, 10%, 45 %, and 63 % for L153F, S186F, A230T, and F493L mutants, respectively. The S186F mutant not only exhibited a dramatic decrease in activity, but also showed no response to WNK3 or to ICD. In contrast, although basal activity was reduced in L153F, A230T, and F493L mutants, the response to WNK3, WNK4, and ICD was similar to wild type NCC. Interestingly, the basal activity of mutant G777E was similar to NCC. This mutant, however, exhibited a 40 % reduction of WNK3-induced activation, while response to ICD was conserved. We conclude that reduction of NCC activity or response to WNK3 is the mechanism by which these rare independent mutations in NCC protect against arterial hypertension."
2008
Background. Gitelman's syndrome (GS), which is caused by homozygous or compound heterozygous mutations of the thiazide-sensitive sodium chloride cotransporter (NCC), usually manifests in children and is associated with low blood pressure. However, the prevalence of heterozygous NCC mutations and their association with blood pressure in children have not yet been studied. Methods. Five hundred unrelated children from the Taipei Children Heart Study were enrolled. Genomic DNA was isolated from peripheral blood and the SLC12A3 gene was amplified by polymerase chain reaction (PCR). The 15 NCC mutations previously identified in Chinese patients with GS were evaluated using restriction fragment length polymorphism (RFLP) analysis. Blood pressure, biochemistry and urine pH were measured. The allelic frequency of heterozygous NCC mutations and their association with low blood pressure were also investigated. Results. RFLP analysis for the 15 NCC mutations revealed heterozygous T60M in 1 child, T163M in 1, S283Y in 4, R642C in 2, W844X in 2, R928C in 9 and R959frameshift in 10 children. The overall incidence of positive heterozygous NCC mutations was ∼2.9%. There were no significant differences in systolic or diastolic blood pressure, biochemical profiles or urine pH between children with heterozygous NCC mutations (n = 29) and non-affected controls (n = 471), except for slightly higher fasting plasma glucose concentrations in NCC-heterozygous children (91 ± 2.3 versus 88 ± 0.4 mg/dL, P < 0.05). Examination among the different NCC mutations showed that these children also had comparable blood pressures. Conclusions. We found a relatively high prevalence of heterozygous NCC mutations in Chinese children, suggesting that GS may not be rare in this population. Heterozygous
NKCC1 and NKCC2: The pathogenetic role of cation-chloride cotransporters in hypertension
This review summarizes the data on the functional significance of ubiquitous (NKCC1) and renal-specific (NKCC2) isoforms of electroneutral sodium, potassium and chloride cotransporters. These carriers contribute to the pathogenesis of hypertension via regulation of intracellular chloride concentration in vascular smooth muscle and neuronal cells and via sensing chloride concentration in the renal tubular fluid, respectively. Both NKCC1 and NKCC2 are inhibited by furosemide and other high-ceiling diuretics widely used for attenuation of extracellular fluid volume. However, the chronic usage of these compounds for the treatment of hypertension and other volume-expanded disorders may have diverse side-effects due to suppression of myogenic response in microcirculatory beds.
Role of the Cation-Chloride-Cotransporters in Cardiovascular Disease
Cells, 2020
The SLC12 family of cation-chloride-cotransporters (CCCs) is comprised of potassium chloride cotransporters (KCCs), which mediate Cl− extrusion and sodium-potassium chloride cotransporters (N[K]CCs), which mediate Cl− loading. The CCCs play vital roles in cell volume regulation and ion homeostasis. The functions of CCCs influence a variety of physiological processes, many of which overlap with the pathophysiology of cardiovascular disease. Although not all of the cotransporters have been linked to Mendelian genetic disorders, recent studies have provided new insights into their functional role in vascular and renal cells in addition to their contribution to cardiovascular diseases. Particularly, an imbalance in potassium levels promotes the pathogenesis of atherosclerosis and disturbances in sodium homeostasis are one of the causes of hypertension. Recent findings suggest hypothalamic signaling as a key signaling pathway in the pathophysiology of hypertension. In this review, we sum...
Increased urinary Na-Cl cotransporter protein in familial hyperkalaemia and hypertension
Nephrology Dialysis Transplantation, 2007
Background. Familial hyperkalaemia and hypertension (FHH), also termed pseudohypoaldosteronism type II, is a rare monogenic form of hypertension caused by mutations in the WNK1 or WNK4 kinases. In vitro expression of WNK4 reduces surface abundance and activity of coexpressed NaCl cotransporter (NCCT). This effect is lost in disease-producing WNK4 mutants. In two mice models of FHH, one expressing two extra copies of mutant WNK4 (Q562E) and another in which a mutant (D561A) WNK4 replaced wild-type WNK4, renal distal tubule hyperplasia with overexpression of NCCT was found. Currently no FHH human renal tissue is available to test for increased distal tubule surface abundance of NCCT. The availability of a unique large family with FHH and the Q565E WNK4 mutation enabled us to investigate this issue in an indirect manner. Methods. Assuming that shedding of NCCT to the urine reflects its abundance in the distal tubule epithelium, we measured urinary NCCT protein in eight subjects of the FHH family and in eight unrelated controls by western blotting. Results. Urinary NCCT protein was about four times higher in FHH than in controls [111.1 ± 40.5 versus 26.1 ± 16.4 densitometry units (P < 0.0001)]. No significant difference in urinary sodium and potassium concentrations was seen between FHH and controls. Conclusions. The increased urinary NCCT in FHH most probably reflects increased NCCT abundance in the apical membrane of distal tubule cells in patients with FHH and the WNK4 mutation and points to the pathogenetic mechanism for the clinical phenotype of FHH and the WNK4 mutation, supporting results in transgenic mice with the same mutation and in knockin mice with another mutation.
What can we learn from erythrocyte Na–K–Cl cotransporter NKCC1 in human hypertension
Pathophysiology, 2007
Fluxes catalyzed by the human Na-K-Cl cotransporter NKCC1 (hNKCC1) were extensively investigated in erythrocytes from essential hypertensive patients. Using different techniques, four hNKCC1 abnormalities were described in a significant proportion of hypertensives: (i) low net sodium extrusion, (ii) high unidirectional inward cotransport, (iii) low apparent affinity for internal sodium and (iv) high maximal cotransport rate. All these four hNKCC1 abnormalities are compatible with an increased net inward cotransport. In hypertensive rat models, an increased net inward cotransport drives more chloride inside the cells, favoring membrane depolarization and hypertension. NKCC1 knock out mice are hypotensive and exhibit a compensatory elevation in renin secretion, apparently due to the lack of a functional NKCC1 in juxtaglomerular granular cells, which normally reduces basal renin release. This latter hypothesis is supported by the observation that human hypertensives with high cotransport have low renin hypertension and increased salidiuretic response to furosemide. Therefore, the human erythrocyte data validates animal studies showing increased net inward fluxes by NKCC1 in primary hypertension.
Proceedings of the National Academy of Sciences, 2003
Mutations in the serine-threonine kinases WNK1 and WNK4 [ w ith n o lysine ( K ) at a key catalytic residue] cause pseudohypoaldosteronism type II (PHAII), a Mendelian disease featuring hypertension, hyperkalemia, hyperchloremia, and metabolic acidosis. Both kinases are expressed in the distal nephron, although the regulators and targets of WNK signaling cascades are unknown. The Cl − dependence of PHAII phenotypes, their sensitivity to thiazide diuretics, and the observation that they constitute a “mirror image” of the phenotypes resulting from loss of function mutations in the thiazide-sensitive Na–Cl cotransporter (NCCT) suggest that PHAII may result from increased NCCT activity due to altered WNK signaling. To address this possibility, we measured NCCT-mediated Na + influx and membrane expression in the presence of wild-type and mutant WNK4 by heterologous expression in Xenopus oocytes. Wild-type WNK4 inhibits NCCT-mediated Na-influx by reducing membrane expression of the cotran...
This review summarizes the data on the functioning of carriers providing electroneutral symport of sodium, potassium, and chloride (Na+,K+,2Cl– cotransport), potassium and chloride (K+,Cl– cotransport), and sodium and chloride (K+,Cl– cotransport) as well as molecular mechanisms of the regulation of these carriers and their physiological significance. We emphasized the involvement of chloridecoupled carriers in the regulation of cell volume and intracellular chloride concentration and novel data on the role of ubiquitous isoform of Na+,K+,2Cl– cotransporter NKCC1 in regulation of vascular smooth muscle contraction and activity of GABAA receptors. Finally, we analyzed the data on activation of NKCC1 in patients with essential hypertension and its role in the longterm maintenance of elevated systemic blood pressure and myogenic response in microcirculatory beds.
Hypertension, 1987
Environmental factors, genetic polymorphisms, and different experimental designs have been the main impediments to evaluating a genetic association between cell membrane cation transport abnormalities and human essential or genetic hypertension. We review the results obtained in the Milan hypertensive strain of rats (MHS) and in its appropriate control normotensive strain (MNS) to illustrate our approach to defining the role of cation transport abnormality in a type of genetic hypertension. Before the development of a difference in blood pressure between the two strains, the comparison of kidney and erythrocyte functions showed that MHS had an increased glomerular filtration rate and urinary output, and lower plasma renin and urine osmolality. Kidney cross-transplantation between the strains showed that hypertension is transplanted with the kidney. Proximal tubular cell volume and sodium content were lower in MHS while sodium transport across the brush border membrane vesicles of MHS was faster. Erythrocytes in MHS were smaller and had lower sodium concentration, and Na +-K + cotransport and passive permeability were faster. The differences in volume, sodium content, and Na +-K + cotransport between erythrocytes of the two strains persisted after transplantation of bone marrow to irradiated F, (MHS x MNS) hybrids. Moreover, in normal segregating F 2 hybrid populations there was a positive correlation between blood pressure and Na +-K + cotransport. These results suggest a genetic and functional link in MHS between cell membrane cation transport abnormalities and hypertension. Thus erythrocyte cell membrane may be used for approaching the problem of defining the genetically determined molecular mechanism underlying the development of a type of essential hypertension.
Regulatory control of the Na–Cl co-transporter NCC and its therapeutic potential for hypertension
Acta Pharmaceutica Sinica B, 2020
Hypertension is the largest risk factor for cardiovascular disease, the leading cause of mortality worldwide. As blood pressure regulation is influenced by multiple physiological systems, hypertension cannot be attributed to a single identifiable etiology. Three decades of research into Mendelian forms of hypertension implicate alterations in the renal tubular sodium handling, particularly the distal convoluted tubule (DCT)-native, thiazide-sensitive Na-Cl cotransporter (NCC). Altered function of the NCC has shown to have profound effects on blood