Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tryptophan-bounded WW domains ofNedd4 bind to the proline-tyrosine (PY) motifs contained in the C-terminal cytoplasmic region of the beta and gamma subunits of the rat amiloride-sensitive sodium channel (ENaC). In patients with Liddle's syndrome, the PY motif is mutated and the channel remains constitutively activated leading to sodium retention and hypertension. Although the function ofNedd4 is unknown, it contains a highly conserved ubiquitin protein ligase domain that may attach ubiquitin to ENaC, targeting it for degradation or it may modulate ENaC activity through another undetermined pathway. Xenopus laevis-derived cells, such as oocytes and the A6 kidney cell line, are important models currently used for the study of ENaC regulation. We describe the X. laevis homologue of Nedd4 (xNedd4). A partial clone, approximately 2.6 Kb, was isolated from an aldosterone-treated A6 cell cDNA library. Further 5' sequence, approximately 1.2 Kb, was obtained using a modified 5' rapid amplification of cDNA (RACE) protocol and cDNA from untreated A6 cells as the substrate. The identity and similarity of xNedd4 with human Nedd4 are approximately 63 and 71%, respectively. xNedd4 contains the C2, ubiquitin protein ligase, and 4 WW domains previously described for Nedd4 from other species.
 ...
PMID:Molecular cloning of Nedd4 from Xenopus laevis. 1052 56

Liddle's syndrome, apparent mineralocorticoid excess (AME) and glucocorticoid remediable aldosteronism (GRA) are inherited diseases characterized by hypertension and low plasma renin activity. Constitutive activation of distal renal epithelial sodium channel (Liddle's syndrome), defect in 11 beta-hydroxysteroid dehydrogenase activity (AME) and unequal crossing over, fusing regulatory sequences of 11 beta-hydroxylase gene to coding sequences of aldosterone synthase gene and forming a new chimeric gene (GRA), cause apparent or real mineralocorticoid excess. This diseases are often being unrecognized and classified as essential hypertension, especially in patients with normal serum potassium level. Family history of hypertension and characteristic serum and urine++ steroid profile direct us to diagnosis, and genetic analysis will confirm it.
 ...
PMID:[Low-renin hypertension and inherited mineralocorticoid diseases]. 1057 60

Liddle's syndrome (or pseudoaldosteronism) is an autosomal dominant form of salt-sensitive hypertension, due to abnormal sodium transport by the renal tubule. To study the pathophysiology of salt sensitivity, a mouse model for Liddle's syndrome has been generated by Cre/loxP-mediated recombination. Under normal salt diet, mice heterozygous (L/+) and homozygous (L/L) for Liddle mutation (L) develop normally during the first 3 mo of life. In these mice, BP is not different from wild type despite evidence for increased sodium reabsorption in distal colon and low plasma aldosterone, suggesting chronic hypervolemia. Under high salt intake, the Liddle mice develop high BP, metabolic alkalosis, and hypokalemia accompanied by cardiac and renal hypertrophy. This animal model reproduces to a large extent a human form of salt-sensitive hypertension and establishes a causal relationship between dietary salt, a gene expressed in kidney and hypertension.
 ...
PMID:A mouse model for Liddle's syndrome. 1058 91

The epithelial Na(+) channel (ENaC) plays a critical role in Na(+) absorption, and mutations in this channel cause diseases of Na(+) homeostasis, including a genetic form of hypertension (Liddle's syndrome). To investigate cAMP-mediated stimulation of ENaC, alpha, beta, and gammaENaC were coexpressed in Fischer rat thyroid epithelia to generate apical Na(+) channels and transepithelial Na(+) current. cAMP agonists stimulated Na(+) current by 70%. Following covalent modification of cysteines introduced into ENaC, cAMP increased the rate of appearance of unmodified channels at the cell surface. In addition, cAMP increased the fluorescent labeling of ENaC at the apical cell surface. Inhibition of vesicle trafficking by incubating epithelia at 15 degrees C prevented the cAMP-mediated stimulation of ENaC. These results suggest that cAMP stimulates Na(+) absorption in part by increasing translocation of ENaC to the cell surface. Stimulation of ENaC by cAMP was dependent on a sequence (PPPXY) in the COOH terminus of each subunit. This sequence is the target for mutations that cause Liddle's syndrome, suggesting that cAMP-mediated translocation of ENaC to the cell surface is defective in this genetic form of hypertension.
 ...
PMID:Liddle's syndrome mutations disrupt cAMP-mediated translocation of the epithelial Na(+) channel to the cell surface. 1061 60

The case of a 74-year-old woman with past history of hypertension and cerebrovascular accident admitted with pneumonia, dehydration, hypernatremia and severe hypokalemic alkalosis is presented. After correction of the hypertonic dehydration, the hypokalemia and alkalosis persisted in spite of aggressive potassium supplementation and the patient became hypertensive. Mineralocorticoid excess was suspected and excluded after extensive endocrinological testing. The use of aldactone failed to revert the abnormalities. Triamterene administration corrected the electrolytes and acid base aberrations, and dramatically improved the blood pressure control. This clinical picture is compatible with the diagnosis of Liddle's syndrome. Our patient exemplifies the unique occurrence of hypokalemic metabolic alkalosis in association with volume contraction at the start of the hospitalization and volume expansion later on her course.
 ...
PMID:Saline-resistant metabolic alkalosis, severe hypokalemia and hypertension in a 74-year-old woman. 1066 85

The epithelial Na+ channel (ENaC) is comprised of three subunits, alpha, beta and gamma, and plays an essential role in Na+ and fluid absorption in the kidney, colon and lung. We had identified proline-rich sequences at the C termini of alpha beta gamma ENaC, which include the sequence PPxY, the PY motif. This sequence in beta or gamma ENaC is deleted or mutated in Liddle's syndrome, a hereditary form of arterial hypertension. Our previous work demonstrated that these PY motifs bind to the WW domains of Nedd4, a ubiquitin protein ligase containing a C2 domain, three or four WW domains and a ubiquitin protein ligase Hect domain. Accordingly, we have recently demonstrated that Nedd4 regulates ENaC function by controlling the number of channels at the cell surface, that this regulation is impaired in ENaC bearing Liddle's syndrome mutations, and that ENaC stability and function are regulated by ubiquitination. The C2 domain is responsible for localizing Nedd4 to the plasma membrane in a Ca(2+)-dependent manner, and in polarized epithelial MDCK cells this localization is primarily apical. In accordance, electrophysiological characterization of ENaC expressed in MDCK cells revealed inhibition of channel activity by elevated intracellular Ca2+ levels. Thus, in response to Ca2+, Nedd4 may be mobilized to the apical membrane via its C2 domain, where it binds ENaC via Nedd4-WW:ENaC-PY motifs' interactions, leading to ubiquitination of the channel by the Nedd4-Hect domain and subsequent channel endocytosis and lysosomal degradation. This process may be at least partially impaired in Liddle's syndrome due to reduced Nedd4 binding, leading to increased retention of ENaC at the cell surface.
 ...
PMID:Regulation of the epithelial Na+ channel by Nedd4 and ubiquitination. 1072 Sep 33

The highly amiloride-sensitive epithelial sodium channel (ENaC) is an apical membrane constituent of cells of many salt-absorbing epithelia. In the kidney, the functional relevance of ENaC expression has been well established. ENaC mediates the aldosterone-dependent sodium reabsorption in the distal nephron and is involved in the regulation of blood pressure. Mutations in genes encoding ENaC subunits are causative for two human inherited diseases: Liddle's syndrome, a severe form of hypertension associated with ENaC hyperfunction, and pseudohypoaldosteronism (PHA-1), a salt-wasting syndrome caused by decreased ENaC function. Transgenic mouse technologies provide a useful tool to study the role of ENaC in vivo. Different mouse lines have been established in which each of the ENaC subunits was affected. The phenotypes observed in these mice demonstrated that each subunit is essential for survival and for regulation of sodium transport in kidney and colon. Moreover, the alpha subunit plays a specific role in the control of fluid absorption in the airways at birth. Such mice can now be used to study the role of ENaC in various organs and can serve as models to understand the pathophysiology of these human diseases.
 ...
PMID:Dysfunction of epithelial sodium transport: from human to mouse. 1076 60

A 54-year-old woman with diabetes mellitus was hospitalized with generalized edema and weakness. She was also found to have hypertension, hypokalemia and metabolic alkalosis. Detailed examination showed subnormal plasma renin activity and plasma aldosterone concentration. Adrenal CT scanning revealed no adrenal tumor. A successful treatment with amiloride established the diagnosis of Liddle's syndrome for the patient. Liddle's syndrome, a rare hereditary disease usually found in young patients, should be considered in the differential diagnosis of hypertension even in elderly individuals.
 ...
PMID:Liddle's syndrome: a report in a middle-aged woman. 1081 31

Sodium and water homeostasis are key to the survival of organisms. Reabsorption of sodium and water occurs throughout the tubule structure of the nephron, the basic functional unit of the kidney, by various transport mechanisms. Altered transport protein function can lead to renal tubular disorders resulting in metabolic alkalosis, hypokalemia, hypertension, and decreased capacity to concentrate urine, for instance. However, recent advances in molecular physiology, molecular genetics and expression cloning systems have aided in unraveling the molecular basis of some renal tubular disorders. This review will examine the molecular basis of Bartter's syndrome, Gitelman's syndrome, Liddle's syndrome, and autosomal nephrogenic diabetes insipidus. An understanding of the molecular basis of these disorders of the human kidney can give us a better understanding of basic renal function of lower mammals and other vertebrates.
 ...
PMID:The molecular basis of renal tubular transport disorders. 1096 27

Our basic understanding of Na(+) transport mechanisms provides unique insights into epithelial transport processes. Unusual clinical syndromes can arise from mutations of these ion transporters. These genetic disorders affect Na(+) balance, resulting in both N(a+) retaining and Na(+) wasting conditions. A major focus has been the epithelial sodium channel (ENaC), which can be activated by mutations (eg, Liddle's syndrome), changes in the response to mineralocorticoids (apparent mineralocorticoid excess syndrome), or production of mineralocorticoids (glucocorticoid-remediable aldosteronism). As a result, we now have clearly defined Mendelian syndromes in which ENaC activity is "dysregulated." This dysregulation leads to systemic hypertension associated with suppressed plasma renin activity, which can be attributed to a primary renal mechanism. Applying these insights to the far more common disorder of low-renin hypertension may shed new light on the underlying pathophysiology of this common form of human hypertension.
 ...
PMID:Aldosterone-related genetic effects in hypertension. 1098 Nov 63


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>