Two polymorphisms in NEDD4L gene and essential hypertension in Chinese Hans - a population-based case-control study

NEDD4L is a promoter for angiogenesis and cell proliferation in human umbilical vein endothelial cells

Dysregulated angiogenesis leads to neovascularization, which can promote or exacerbate various diseases. Previous studies have proved that NEDD4L plays an important role in hypertension and atherosclerosis. Hence, we hypothesized that NEDD4L may be a critical regulator of endothelial cell (EC) function. This study aimed to define the role of NEDD4L in regulating EC angiogenesis and elucidate their underlying mechanisms. Loss- and gain-of-function of NEDD4L detected the angiogenesis and mobility role in human umbilical vein endothelial cells (HUVECs) using Matrigel tube formation assay, cell proliferation and migration. Pharmacological pathway inhibitors and western blot were used to determine the underlying mechanism of NEDD4L-regulated endothelial functions. Knockdown of NEDD4L suppressed tube formation, cell proliferation and cell migration in HUVECs, whereas NEDD4L overexpression promoted these functions. Moreover, NEDD4L-regulated angiogenesis and cell progression are associated with the phosphorylation of Akt, Erk1/2 and eNOS and the expression of VEGFR2 and cyclin D1 and D3. Mechanically, further evidence was confirmed by using Akt blocker MK-2206, Erk1/2 blocker U0126 and eNOS blocker L-NAME. Overexpression NEDD4L-promoted angiogenesis, cell migration and cell proliferation were restrained by these inhibitors. In addition, overexpression NEDD4L-promoted cell cycle-related proteins cyclin D1 and D3 were also suppressed by Akt blocker MK-2206, Erk1/2 blocker U0126 and eNOS blocker L-NAME. Our results demonstrated a novel finding that NEDD4L promotes angiogenesis and cell progression by regulating the Akt/Erk/eNOS pathways.

Research progress of Nedd4L in cardiovascular diseases

Post-translational modifications (PTMs) are a covalent processing process of proteins after translation. Proteins are capable of playing their roles only after being modified, so as to maintain the normal physiological function of cells. As a key modification of protein post-translational modification, ubiquitination is an essential element, which forms an enzyme-linked reaction through ubiquitin-activating enzyme, ubiquitin binding enzyme, and ubiquitin ligase, aiming to regulate the expression level and function of cellular proteins. Nedd4 family is the largest group of ubiquitin ligases, including 9 members, such as Nedd4-1, Nedd4L (Nedd4-2), WWP1, WWP2, ITCH, etc. They could bind to substrate proteins through their WW domain and play a dominant role in the ubiquitination process, and then participate in various pathophysiological processes of cardiovascular diseases (such as hypertension, myocardial hypertrophy, heart failure, etc.). At present, the role of Nedd4L in the cardiovascular field is not fully understood. This review aims to summarize the progress and mechanism of Nedd4L in cardiovascular diseases, and provide potential perspective for the clinical treatment or prevention of related cardiovascular diseases by targeting Nedd4L.

The Renal Physiology of Pendrin-Positive Intercalated Cells

Intercalated cells (ICs) are found in the connecting tubule and the collecting duct. Of the three IC subtypes identified, type B intercalated cells are one of the best characterized and known to mediate Cl- absorption and HCO3- secretion, largely through the anion exchanger pendrin. This exchanger is thought to act in tandem with the Na+-dependent Cl-/HCO3- exchanger, NDCBE, to mediate net NaCl absorption. Pendrin is stimulated by angiotensin II and aldosterone administration via the angiotensin type 1a and the mineralocorticoid receptors, respectively. It is also stimulated in models of metabolic alkalosis, such as with NaHCO3 administration. In some rodent models, pendrin-mediated HCO3- secretion modulates acid-base balance. However, of probably more physiological or clinical significance is the role of these pendrin-positive ICs in blood pressure regulation, which occurs, at least in part, through pendrin-mediated renal Cl- absorption, as well as their effect on the epithelial Na+ channel, ENaC. Aldosterone stimulates ENaC directly through principal cell mineralocorticoid hormone receptor (ligand) binding and also indirectly through its effect on pendrin expression and function. In so doing, pendrin contributes to the aldosterone pressor response. Pendrin may also modulate blood pressure in part through its action in the adrenal medulla, where it modulates the release of catecholamines, or through an indirect effect on vascular contractile force. In addition to its role in Na+ and Cl- balance, pendrin affects the balance of other ions, such as K+ and I-. This review describes how aldosterone and angiotensin II-induced signaling regulate pendrin and the contribution of pendrin-positive ICs in the kidney to distal nephron function and blood pressure.

The Role of Intercalated Cell Nedd4-2 in BP Regulation, Ion Transport, and Transporter Expression

BackgroundNedd4-2 is an E3 ubiquitin-protein ligase that associates with transport proteins, causing their ubiquitylation, and then internalization and degradation. Previous research has suggested a correlation between Nedd4-2 and BP. In this study, we explored the effect of intercalated cell (IC) Nedd4-2 gene ablation on IC transporter abundance and function and on BP.Methods We generated IC Nedd4-2 knockout mice using Cre-lox technology and produced global pendrin/Nedd4-2 null mice by breeding global Nedd4-2 null (Nedd4-2^-/- ) mice with global pendrin null (Slc26a4^-/- ) mice. Mice ate a diet with 1%-4% NaCl; BP was measured by tail cuff and radiotelemetry. We measured transepithelial transport of Cl^- and total CO₂ and transepithelial voltage in cortical collecting ducts perfused in vitro Transporter abundance was detected with immunoblots, immunohistochemistry, and immunogold cytochemistry.Results IC Nedd4-2 gene ablation markedly increased electroneutral Cl^-/HCO₃^- exchange in the cortical collecting duct, although benzamil-, thiazide-, and bafilomycin-sensitive ion flux changed very little. IC Nedd4-2 gene ablation did not increase the abundance of type B IC transporters, such as AE4 (Slc4a9), H⁺-ATPase, barttin, or the Na⁺-dependent Cl^-/HCO₃^- exchanger (Slc4a8). However, IC Nedd4-2 gene ablation increased CIC-5 total protein abundance, apical plasma membrane pendrin abundance, and the ratio of pendrin expression on the apical membrane to the cytoplasm. IC Nedd4-2 gene ablation increased BP by approximately 10 mm Hg. Moreover, pendrin gene ablation eliminated the increase in BP observed in global Nedd4-2 knockout mice.Conclusions IC Nedd4-2 regulates Cl^-/HCO₃^- exchange in ICs., Nedd4-2 gene ablation increases BP in part through its action in these cells.

Nedd4-2 haploinsufficiency causes hyperactivity and increased sensitivity to inflammatory stimuli

Nedd4-2 (NEDD4L in humans) is a ubiquitin protein ligase best known for its role in regulating ion channel internalization and turnover. Nedd4-2 deletion in mice causes perinatal lethality associated with increased epithelial sodium channel (ENaC) expression in lung and kidney. Abundant data suggest that Nedd4-2 plays a role in neuronal functions and may be linked to epilepsy and dyslexia in humans. We used a mouse model of Nedd4-2 haploinsufficiency to investigate whether an alteration in Nedd4-2 levels of expression affects general nervous system functions. We found that Nedd4-2 heterozygous mice are hyperactive, have increased basal synaptic transmission and have enhanced sensitivity to inflammatory pain. Thus, Nedd4-2 heterozygous mice provide a new genetic model to study inflammatory pain. These data also suggest that in human, SNPs affecting NEDD4L levels may be involved in the development of neuropsychological deficits and peripheral neuropathies and may help unveil the genetic basis of comorbidities.

NEDD4-2 (NEDD4L): the ubiquitin ligase for multiple membrane proteins

NEDD4-2 (also known as NEDD4L, neural precursor cell expressed developmentally down-regulated 4-like) is a ubiquitin protein ligase of the Nedd4 family which is known to bind and regulate a number of membrane proteins to aid in their internalization and turnover. Several of the NEDD4-2 substrates include ion channels, such as the epithelial and voltage-gated sodium channels. Given the critical function of NEDD4-2 in regulating membrane proteins, this ligase is essential for the maintenance of cellular homeostasis. In this article we review the biology and function of this important ubiquitin-protein ligase and discuss its pathophysiological significance.

A functional variant of NEDD4L is associated with obesity and related phenotypes in a Han population of Southern China

NEDD4L is a candidate gene for hypertension, both functionally and genetically. Recently, studies showed evidence for the association of NEDD4L with obesity, a key intermediate phenotype in hypertension. To further investigate the relationship between NEDD4L and body mass-related phenotypes, we genotyped three common variants (rs2288774, rs3865418 and rs4149601) in a population-based study of 892 unrelated Han Cantonese using the Sequenom MALDI-TOF-MS platform. Allele frequencies and genotype distribution were calculated in lean controls and overweight/obese cases and analyzed for association by the Chi-squared test and Logistic regression. Linear regression analysis was used to analyze the effect of individual genotypes on quantitative traits. Multivariate analyses demonstrated that the minor allele of rs4149601(A = 20.9%) was associated with a 2.60 kg, 2.78 cm and 0.97 kg/m² decrease per allele copy in weight, waist and BMI, respectively. Carriers of this allele also had a significant lower risk of overweight/obesity (p < 0.0001, OR = 0.52, 95% CI: 0.37–0.74) as compared to non-carriers. However, no significant association between genotypes at rs2288774 and rs3865418 and covariate-adjusted overweight/obesity or any related phenotypes was observed. These results suggested that the functional variant of NEDD4L, rs4149601, may be associated with obesity and related phenotypes, and further genetic and functional studies are required to understand its role in the manifestation of obesity.

Genetic analysis of diabetic nephropathy on chromosome 18 in African Americans: linkage analysis and dense SNP mapping

Genetic studies in Turkish, Native American, European American, and African American (AA) families have linked chromosome 18q21.1-23 to susceptibility for diabetes-associated nephropathy. In this study, we have carried out fine linkage mapping in the 18q region previously linked to diabetic nephropathy in AAs by genotyping both microsatellite and single nucleotide polymorphisms (SNPs) for linkage analysis in an expanded set of 223 AA families multiplexed for type 2 diabetes associated ESRD (T2DM-ESRD). Several approaches were used to evaluate evidence of linkage with the strongest evidence for linkage in ordered subset analysis with an earlier age of T2DM diagnosis compared to the remaining pedigrees (LOD 3.9 at 90.1 cM, ΔP = 0.0161, NPL P value = 0.00002). Overall, the maximum LODs and LOD-1 intervals vary in magnitude and location depending upon analysis. The linkage mapping was followed up by performing a dense SNP map, genotyping 2,814 SNPs in the refined LOD-1 region in 1,029 AA T2DM-ESRD cases and 1,027 AA controls. Of the top 25 most associated SNPs, 10 resided within genic regions. Two candidate genes stood out: NEDD4L and SERPINB7. SNP rs512099, located in intron 1 of NEDD4L, was associated under a dominant model of inheritance [P value = 0.0006; Odds ratio (95% Confidence Interval) OR (95% CI) = 0.70 (0.57-0.86)]. SNP rs1720843, located in intron 2 of SERPINB7, was associated under a recessive model of inheritance [P value = 0.0017; OR (95% CI) = 0.65 (0.50-0.85)]. Collectively, these results suggest that multiple genes in this region may influence diabetic nephropathy susceptibility in AAs.

Intracellular ubiquitylation of the epithelial Na+ channel controls extracellular proteolytic channel activation via conformational change

The epithelial Na(+) channel ENaC is a key player in the maintenance of whole body Na(+) balance, and consequently of blood pressure. It is tightly regulated by numerous signaling pathways including ubiquitylation via the ubiquitin-protein ligase Nedd4-2. This mechanism is itself under the control of several kinases, which phosphorylate Nedd4-2, thereby interfering with ENaC/Nedd4-2 interaction, or by Usp2-45, which binds to and deubiquitylates ENaC. Another, different regulatory mechanism concerns the proteolytic activation of ENaC, during which the channel is cleaved on its luminal side by intracellular convertases such as furin, and further activated by extracellular proteases such as CAP-1. This process is regulated as well but the underlying mechanisms are not understood. Previously, evidence was provided that the ubiquitylation status of ENaC may affect the cleavage of the channel. When ubiquitylation of ENaC was reduced, either by co-expressing Usp2-45, or mutating either the ENaC PY-motifs (i.e. the binding sites for Nedd4-2) or intracellular lysines (i.e. ubiquitylation sites), the level of channel cleavage was increased. Here we demonstrate that lysine-mutated ENaC channels are not ubiquitylated at the cell surface, are preferentially cleaved, and Usp2-45 does not affect their cleavage efficiency. We further show by limited proteolysis that the intracellular ubiquitylation status of ENaC affects the extracellular conformation of αENaC, by demonstrating that non-ubiquitylated channels are more efficiently cleaved when treated with extracellularly added trypsin or chymotrypsin. These results present a new paradigm in which an intracellular, post-translational modification (e.g. ubiquitylation) of a transmembrane protein can affect its extracellular conformation.

Identification of candidate genes for dyslexia susceptibility on chromosome 18

BACKGROUND

Six independent studies have identified linkage to chromosome 18 for developmental dyslexia or general reading ability. Until now, no candidate genes have been identified to explain this linkage. Here, we set out to identify the gene(s) conferring susceptibility by a two stage strategy of linkage and association analysis.

METHODOLOGY/PRINCIPAL FINDINGS

Linkage analysis: 264 UK families and 155 US families each containing at least one child diagnosed with dyslexia were genotyped with a dense set of microsatellite markers on chromosome 18. Association analysis: Using a discovery sample of 187 UK families, nearly 3000 SNPs were genotyped across the chromosome 18 dyslexia susceptibility candidate region. Following association analysis, the top ranking SNPs were then genotyped in the remaining samples. The linkage analysis revealed a broad signal that spans approximately 40 Mb from 18p11.2 to 18q12.2. Following the association analysis and subsequent replication attempts, we observed consistent association with the same SNPs in three genes; melanocortin 5 receptor (MC5R), dymeclin (DYM) and neural precursor cell expressed, developmentally down-regulated 4-like (NEDD4L).

CONCLUSIONS

Along with already published biological evidence, MC5R, DYM and NEDD4L make attractive candidates for dyslexia susceptibility genes. However, further replication and functional studies are still required.

Genetic variation of NEDD4L is associated with essential hypertension in female Kazakh general population: a case-control study

Background

Hypertension affects > 18.8% of adults in China. Indeed, hypertension is the most prevalent risk factor for cardiovascular morbidity and mortality worldwide. Genetic variation is thought to contribute to the etiology of hypertension. NEDD4L is a candidate gene for hypertension, both functionally and genetically. The purpose of the current study was to investigate the relationship between the variation in NEDD4L and essential hypertension in Kazakh, which is a relatively isolated population with a pure genetic background and is an ideal population to study genetic mechanisms of hypertension.

Methods

We screened the promoter and exons of NEDD4L in 94 Kazakh hypertensive individuals to identify representative variations. Then, by genotyping the representative variations in the Kazakh general population, a case-control study was conducted.

Results

By systemically screening variations of NEDD4L, we did not identify any functional mutations in NEDD4L. A new common variation (296921-296923delTTG), which is not found in the NCBI database, was identified. Three representative variations (296921-296923delTTG, rs2288774, and rs2288775) were successfully genotyped in the Kazakh general population. The distribution of the dominant model (AA vs. AG+GG) of rs2288775, the additive model, and the recessive model (II+ID vs. DD) of 296921-296923delTTG differed significantly between the cases and controls in females (P = 0.040, P = 0.024, and P = 0.007, respectively). After adjusting for confounding factors, logistic regression analysis showed that rs2288775 (in the dominant model) and 296921-296923delTTG (in the recessive model) were significantly associated with hypertension (rs2288775: OR = 1.479, 95% CI = 1.011-2.064, p = 0.044; and 296921-296923delTTG: OR = 1.908, 95% CI = 1.020-3.568, p = 0.043) in females. The frequency of the D-C-G haplotype was significantly higher for cases than for controls in females (P = 0.020). There was a significant interaction between the NEDD4L genotype and gender (P for interaction: 0.045 for rs2288775 and 0.064 for 296921-296923delTTG), but there was no significant interaction between the NEDD4L genotype and smoking (P for interaction: 0.616 for rs2288775 and 0.447 for 296921-296923delTTG). For females and total participants, the urinary Na excretion rate was significantly lower in the DD than the I/I+I/D individuals (P = 0.032 and P = 0.027 respectively).

Conclusion

The genetic variations of NEDD4L may be associated with essential hypertension in females in the Kazakh general population.