Hypertension resistance polymorphisms in ROMK (Kir1.1) alter channel function by different mechanisms

Fang, Liang; Li, Dimin; Welling, Paul A.

doi:10.1152/ajprenal.00257.2010

Cited by 29 publications

(24 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results presented here, however, are supportive of the finding that the rare mutations are correlated with reduced blood pressure, since on average our variants have Ͼ50% reduced activity in HEK cells compared with wild-type hNKCC2, and in general the corresponding blood pressures are below average (14). Interestingly, a recent study which examined the functional consequences of the ROMK mutations identified by Ji et al came to a similar conclusion by determining that polymorphisms in ROMK inhibit channel function by altering protein processing and channel-gating properties (7).…”

Section: Discussionsupporting

confidence: 59%

Rare mutations in the human Na-K-Cl cotransporter (NKCC2) associated with lower blood pressure exhibit impaired processing and transport function

Monette

Rinehart

Lifton

et al. 2011

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

The Na-K-Cl cotransporter (NKCC2) is the major salt transport pathway in the thick ascending limb of Henle's loop and is part of the molecular mechanism for blood pressure regulation. Recent screening of ∼3,000 members of the Framingham Heart Study identified nine rare independent mutations in the gene encoding NKCC2 (SLC12A1) associated with clinically reduced blood pressure and protection from hypertension (Ji WZ, Foo JN, O'Roak BJ, Zhao H, Larson MG, Simon DB, Newton-Cheh C, State M, Levy D, Lifton RP. Nat Genet 40: 592-599, 2008). To investigate their functional consequences, we introduced the nine mutations in human NKCC2A and examined protein function, expression, localization, regulation, and ion transport kinetics using heterologous expression in Xenopus laevis oocytes and HEK-293 cells. When expressed in oocytes, four of the mutants (T235M, R302W, L505V, and P569H) exhibited reduced transport function compared with wild-type. In HEK-293 cells, the same four mutants exhibited reduced function, and in addition N399S and P1083A had significantly lower activity than wild-type. The two most functionally impaired mutants (R302W and L505V) exhibited dramatically diminished production of complex-glycosylated protein and a decrease in or absence of plasma membrane localization, indicative of a processing defect. All of the functional human (h) NKCC2A variants were regulated by changes in oocyte volume and intracellular chloride in HEK cells, but P254A and N399S exhibited a lower constitutive activity in HEK cells. The P569H mutant exhibited a 50% reduction in sodium affinity compared with wild-type, predicting lower transport activity at lower intratubular salt concentrations, while the P254A mutant exhibited a 35% increase in rubidium affinity. We conclude that defects in NKCC2 processing, transport turnover rate, regulation, and ion affinity contribute to impaired transport function in six of the nine identified mutants, providing support for the predictive approach of Ji et al. to identify functionally important residues by sequence conservation. Such mutations in hNKCC2A are likely to reduce renal salt reabsorption, providing a mechanism for lower blood pressure.

show abstract

Section: Discussionsupporting

confidence: 59%

Rare mutations in the human Na-K-Cl cotransporter (NKCC2) associated with lower blood pressure exhibit impaired processing and transport function

Monette

Rinehart

Lifton

et al. 2011

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

show abstract

“…Together, these three studies (1,2,9) provide strong support for the selection criteria employed by Ji et al (5) to identify functional variants. Even when the potential imperfections of heterologous expression are taken into consideration, it would appear that at least 90% of the identified variants have a proven functional effect.…”

supporting

confidence: 52%

“…The study by Acuna et al also evaluated the inferred variants in SLC12A3 and found that all five of the mutations resulted in modest but statistically significant reductions in NCC activity. The third paper was an analysis of inferred variants in KCNJ1, reported recently by Fang et al (2). In their study, all of the five identified ROMK hypertension resistance variants behaved as predicted, exhibiting measurable loss of function.…”

mentioning

confidence: 85%

Toward an understanding of hypertension resistance

Subramanya

Welling

2011

American Journal of Physiology-Renal Physiology

Self Cite

View full text Add to dashboard Cite

“…39 Therefore, investigating how cholesterol and PI(4,5)P 2 regulate ENaC in microvilli would serve as interesting topics for our future studies. Recent studies have identified ROMK polymorphisms that prevent the channel trafficking to the plasma membrane 40 and also shown that high dietary potassium promotes ROMK trafficking to the plasma membrane. 25 It would be interesting to investigate whether ROMK polymorphisms and high dietary potassium could alter the planar region localization of ROMK channels.…”

Section: Discussionmentioning

confidence: 99%

Lovastatin-Induced Phosphatidylinositol-4-Phosphate 5-Kinase Diffusion from Microvilli Stimulates ROMK Channels

Liu

Yang

et al. 2015

Journal of the American Society of Nephrology

View full text Add to dashboard Cite

We recently showed that lovastatin attenuates cyclosporin A (CsA)-induced damage of cortical collecting duct (CCD) principal cells by reducing intracellular cholesterol. Previous studies showed that, in cell expression models or artificial membranes, exogenous cholesterol directly inhibits inward rectifier potassium channels, including Kir1.1 (Kcnj1; the gene locus for renal outer medullary K + [ROMK1] channels). Therefore, we hypothesized that lovastatin might stimulate ROMK1 by reducing cholesterol in CCD cells. Western blots showed that mpkCCD c14 cells express ROMK1 channels with molecular masses that approximate the molecular masses of ROMK1 in renal tubules detected before and after treatment with DTT. Confocal microscopy showed that ROMK1 channels were not in the microvilli, where cholesterolrich lipid rafts are located, but rather, the planar regions of the apical membrane of mpkCCD c14 cells. Furthermore, phosphatidylinositol-4,5-bisphosphate [PI(4,5)P 2 ], an activator of ROMK channels, was detected mainly in the microvilli under resting conditions along with the kinase responsible for PI(4,5) P 2 synthesis, phosphatidylinositol-4-phosphate 5-kinase, type I g [PI(4)P5K I g], which may explain the low basal open probability and increased sensitivity to tetraethylammonium observed here for this channel. Notably, lovastatin induced PI(4)P5K I g diffusion into planar regions and elevated PI(4,5)P 2 and ROMK1 open probability in these regions through a cholesterol-associated mechanism. However, exogenous cholesterol alone did not induce these effects. These results suggest that lovastatin stimulates ROMK1 channels, at least in part, by inducing PI(4,5)P 2 synthesis in planar regions of the renal CCD cell apical membrane, suggesting that lovastatin could reduce cyclosporin-induced nephropathy and associated hyperkalemia.

show abstract

Hypertension resistance polymorphisms in ROMK (Kir1.1) alter channel function by different mechanisms

Abstract: Fang L, Li D, Welling PA. Hypertension resistance polymorphisms in ROMK (Kir1.1) alter channel function by different mechanisms.

Cited by 29 publications

References 25 publications

Rare mutations in the human Na-K-Cl cotransporter (NKCC2) associated with lower blood pressure exhibit impaired processing and transport function

Rare mutations in the human Na-K-Cl cotransporter (NKCC2) associated with lower blood pressure exhibit impaired processing and transport function

Toward an understanding of hypertension resistance

Lovastatin-Induced Phosphatidylinositol-4-Phosphate 5-Kinase Diffusion from Microvilli Stimulates ROMK Channels

Contact Info

Product

Resources

About