YOU ARE NOW CONNECTED TO THE TOXLINE (1981 FORWARD, NON-ROYALTY) FILE. ==LIDDLE'S SYNDROME== 6 AUTHOR Hansson JH AUTHOR Nelson-Williams C AUTHOR Suzuki H AUTHOR Schild L AUTHOR Shimkets R AUTHOR Lu Y AUTHOR Canessa C AUTHOR Iwasaki T AUTHOR Rossier B AUTHOR Lifton RP TITLE Hypertension caused by a truncated epithelial sodium channel gamma subunit: genetic heterogeneity of Liddle syndrome. SOURCE Nat Genet; VOL 11, ISS 1, 1995, P76-82 ABSTRACT Sensitivity of blood pressure to dietary salt is a common feature in subjects with hypertension. These features are exemplified by the mendelian disorder, Liddle's syndrome, previously shown to arise from constitutive activation of the renal epithelial sodium channel due to mutation in the beta subunit of this channel. We now demonstrate that this disease can also result from a mutation truncating the carboxy terminus of the gamma subunit of this channel; this truncated subunit also activates channel activity. These findings demonstrate genetic heterogeneity of Liddle's syndrome, indicate independent roles of beta and gamma subunits in the negative regulation of channel activity, and identify a new gene in which mutation causes a salt-sensitive form of human hypertension. YOU ARE NOW CONNECTED TO THE MEDLINE (1994 - 97) FILE. 13 AUTHOR Gadallah MF AUTHOR Abreo K AUTHOR Work J TITLE Liddle's syndrome, an underrecognized entity: a report of four cases, including the first report in black individuals [see comments] SOURCE Am J Kidney Dis 1995 Jun;25(6):829-35 ABSTRACT Liddle's syndrome, a rare cause of hypokalemic hypertension, is characterized by a renal tubular sodium channel defect resulting in excessive sodium absorption and concomitant potassium wasting. In this disorder, although the clinical manifestations resemble primary aldosteronism, serum and urine aldosterone are suppressed. The syndrome is transmitted in an autosomal dominant pattern. It has been reported previously in white and oriental populations but not in the black individuals. We identified four patients (two of whom are black) in our nephrology clinic, with severe hypokalemic hypertension not correctly diagnosed for several years. All patients underwent an extensive work-up for secondary hypertension because of persistent severe hypertension (average blood pressure, 210/130 mm Hg) despite high-dose multi-drug therapy. Primary aldosteronism was excluded because of low serum aldosterone. Cushing's syndrome, pheochromocytoma, renal artery stenosis, and enzymatic deficiencies of cortisol synthesis (11 beta-hydroxylase, 17 alpha-hydroxylase, 5 beta-reductase, and 11 beta-hydroxysteroid dehydrogenase) were ruled out with extensive endocrine and radiologic studies. Once the diagnosis of Liddle's syndrome was suspected, all patients were treated with either triamterene or ameloride, with resolution of hypokalemia and correction of hypertension occurring within 5 to 7 days. Our findings suggest that Liddle's syndrome can occur in the black population. Although the actual incidence of this syndrome remains unknown, it may be significantly more common than we are led to believe since it is inherited in a Mendelian pattern. Whether there is a subset of low-renin, salt-sensitive black hypertensive patients who have the same or similar sodium channel defect remains to be elucidated. 16 AUTHOR Warnock DG AUTHOR Bubien JK TITLE Liddle syndrome: clinical and cellular abnormalities. SOURCE Hosp Pract (Off Ed) 1994 Jul 15;29(7):95-8, 104-5 ABSTRACT Clinical findings resemble those of primary hyperaldosteronism, except that aldosterone secretion is negligible. The fault appears to lie with continuously avid sodium channels in the distal nephron, resulting in excessive salt absorption, potassium wasting, and severe hypertension. Insights gained in this disorder may help clarify more common forms of low-renin hypertension. 3 AUTHOR Ismailov II AUTHOR Berdiev BK AUTHOR Fuller CM AUTHOR Bradford AL AUTHOR Lifton RP AUTHOR Warnock DG AUTHOR Bubien JK AUTHOR Benos DJ TITLE Peptide block of constitutively activated Na+ channels in Liddle's disease. SOURCE Am J Physiol 1996 Jan;270(1 Pt 1):C214-23 ABSTRACT Hypertension is a multifactorial disorder that results in an increased risk of cardiovascular and end-stage renal disease. Liddle's disease represents a specific hypertensive disease and expresses itself in the human population as an autosomal dominant trait. Recent experimental evidence indicates that patients with Liddle's disease have constitutively active amiloride-sensitive Na+ channels and that these channels are phenotypically expressed in lymphocytes obtained from normal and affected members of the original Liddle's kindred. Linkage analysis indicates that this disease results from a deletion of the carboxy-terminal region of the beta-subunit of a recently cloned epithelial Na+ channel (ENaC). We report the successful immunopurification and reconstitution of both normal and constitutively active lymphocyte Na+ channels into planar lipid bilayers. These channels display all of the characteristics typical of renal Na+ channels, including sensitivity to protein kinase A phosphorylation. We demonstrate that gating of normal Na+ channels is removed by cytoplasmic trypsin digestion and that the constitutively active Liddle's Na+ channels are blocked by a beta- or gamma-ENaC carboxy-terminal peptide in a GTP-dependent fashion. 4 AUTHOR Bubien JK AUTHOR Ismailov II AUTHOR Berdiev BK AUTHOR Cornwell T AUTHOR Lifton RP AUTHOR Fuller CM AUTHOR Achard JM AUTHOR Benos DJ AUTHOR Warnock DG TITLE Liddle's disease: abnormal regulation of amiloride-sensitive Na+ channels by beta-subunit mutation. SOURCE Am J Physiol 1996 Jan;270(1 Pt 1):C208-13 ABSTRACT Liddle's disease is an autosomal dominant genetic disorder characterized by severe low renin hypertension ("pseudoaldosteronism") that has been genetically linked to a locus on chromosome 16 encoding the beta-subunit of an amiloride-sensitive Na+ channel (ASSC) (15). Peripheral blood lymphocytes (PBL) express ASSC that are functionally indistinguishable from those expressed by Na(+)-reabsorbing renal epithelial cells (3, 5). The amiloride-sensitive Na+ conductance in PBL from affected and unaffected individuals from the original Liddle's pedigree was examined using whole cell patch clamp. Typically, the basal Na+ currents in cells from affected individuals were maximally activated. Basal Na+ currents in cells from unaffected individuals were minimal and could be maximally activated by superfusion with 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP). Affected cells could not be further stimulated with CPT-cAMP. Superfusion with a supermaximal concentration of amiloride (2 microM) inhibited both the cAMP-activated Na+ conductance in unaffected cells and the constitutively activated inward conductance in affected cells. Cytosolic addition of a peptide identical to the terminal 10 amino acids of the truncated beta-subunit normalized the cAMP-mediated but not the pertussis toxin-induced regulation of the mutant ASSC. The findings show that lymphocyte ASSC are constitutively activated in affected individuals, that a mutation of the beta-subunit alters ASSC responsiveness to specific regulatory effectors, and that the cellular mechanism responsible for the pathophysiology of Liddle's disease is abnormal regulation of Na+ channel activity. These findings have important diagnostic and therapeutic implications and provide a cellular phenotype for the diagnosis of pseudoaldosteronism. 9 AUTHOR Snyder PM AUTHOR Price MP AUTHOR McDonald FJ AUTHOR Adams CM AUTHOR Volk KA AUTHOR Zeiher BG AUTHOR Stokes JB AUTHOR Welsh MJ TITLE Mechanism by which Liddle's syndrome mutations increase activity of a human epithelial Na+ channel. SOURCE Cell 1995 Dec 15;83(6):969-78 ABSTRACT Liddle's syndrome is an inherited form of hypertension caused by mutations that truncate the C-terminus of human epithelial Na+ channel (hENaC) subunits. Expression of truncated beta and gamma hENaC subunits increased Na+ current. However, truncation did not alter single-channel conductance or open state probability, suggesting there were more channels in the plasma membrane. Moreover, truncation of the C-terminus of the beta subunit increased apical cell-surface expression of hENaC in a renal epithelium. We identified a conserved motif in the C-terminus of all three subunits that, when mutated, reproduced the effect of Liddle's truncations. Further, both truncation of the C-terminus and mutation of the conserved C-terminal motif increased surface expression of chimeric proteins containing the C-terminus of beta hENaC. Thus, by deleting a conserved motif, Liddle's mutations increase the number of Na+ channels in the apical membrane, which increases renal Na+ absorption and creates a predisposition to hypertension.