scholarly journals KCNJ5 mutations in the National Institutes of Health cohort of patients with primary hyperaldosteronism: an infrequent genetic cause of Conn's syndrome

2012 ◽  
Vol 19 (3) ◽  
pp. 255-260 ◽  
Author(s):  
Paraskevi Xekouki ◽  
Michael M Hatch ◽  
Lin Lin ◽  
De Alexandre Rodrigo ◽  
Monalisa Azevedo ◽  
...  

KCNJ5 mutations were recently described in primary hyperaldosteronism (PH or Conn's syndrome). The frequency of these mutations in PH and the way KCNJ5 defects cause disease remain unknown. A total of 53 patients with PH have been seen at the National Institutes of Health over the last 12 years. Their peripheral and tumor DNAs (the latter from 16 that were operated) were screened for KCNJ5 mutations; functional studies on the identified defects were performed after transient transfection. Only two mutations were identified, and both in the tumor DNA only. There were no germline sequencing defects in any of the patients except for known synonymous variants of the KCNJ5 gene. One mutation was the previously described c.G451C alteration; the other was a novel one in the same codon: c.G451A; both lead to the same amino acid substitution (G151R) in the KCNJ5 protein. Functional studies confirmed previous findings that both mutations caused loss of channel selectivity and a positive shift in the reversal potential. In conclusion, the KCNJ5 protein was strongly expressed in the zona glomerulosa of normal adrenal glands but showed variable expression in the aldosterone-producing adenomas with and without mutation. The rate of KCNJ5 mutations among patients with PH and/or their tumors is substantially lower than what was previously reported. The G151R amino acid substitution appears to be the most frequent one so far detected in PH, despite additional nucleotide changes. The mutation causes loss of this potassium channel's selectivity and may assist in the design of new therapies for PH.

2000 ◽  
Vol 182 (9) ◽  
pp. 2567-2573 ◽  
Author(s):  
Nobuo Kido ◽  
Hidemitsu Kobayashi

ABSTRACT wbdA is a mannosyltransferase gene that is involved in synthesis of the Escherichia coli O9a polysaccharide, a mannose homopolymer with a repeating unit of 2-αMan-1,2-αMan-1,3-αMan-1,3-αMan-1. The equivalent structural O polysaccharide in the E. coli O9 andKlebsiella O3 strains is 2-αMan-1,2-αMan-1,2-αMan-1,3-αMan-1,3-αMan-1, with an excess of one mannose in the 1,2 linkage. We have cloned wbdAgenes from these O9 and O3 strains and shown by genetic and functional studies that wbdA is the only gene determining the O-polysaccharide structure of O9 or O9a. Based on functional analysis of chimeric genes and site-directed mutagenesis, we showed that a single amino acid substitution, C55R, in WbdA of E. coli O9 converts the O9 polysaccharide into O9a. DNA sequencing revealed the substitution to be conserved in other E. coli O9a strains. The reverse substitution, R55C, in WbdA of E. coli O9a resulted in lipopolysaccharide synthesis showing no ladder profile instead of the conversion of O9a to O9. This suggests that more than one amino acid substitution in WbdA is required for conversion from O9a to O9.


2012 ◽  
Vol 97 (8) ◽  
pp. E1532-E1539 ◽  
Author(s):  
Evangelia Charmandari ◽  
Amalia Sertedaki ◽  
Tomoshige Kino ◽  
Christina Merakou ◽  
Dax A. Hoffman ◽  
...  

Abstract Context: Aldosterone production in the adrenal zona glomerulosa is mainly regulated by angiotensin II, [K+], and ACTH. Genetic deletion of subunits of K+-selective leak (KCNK) channels TWIK-related acid sensitive K+-1 and/or TWIK-related acid sensitive K+-3 in mice results in primary hyperaldosteronism, whereas mutations in the KCNJ5 (potassium inwardly rectifying channel, subfamily J, member 5) gene are implicated in primary hyperaldosteronism and, in certain cases, in autonomous glomerulosa cell proliferation in humans. Objective: The objective of the study was to investigate the role of KCNK3, KCNK5, KCNK9, and KCNJ5 genes in a family with primary hyperaldosteronism and early-onset hypertension. Patients and Methods: Two patients, a mother and a daughter, presented with severe primary hyperaldosteronism, bilateral massive adrenal hyperplasia, and early-onset hypertension refractory to medical treatment. Genomic DNA was isolated and the exons of the entire coding regions of the above genes were amplified and sequenced. Electrophysiological studies were performed to determine the effect of identified mutation(s) on the membrane reversal potentials. Results: Sequencing of the KCNJ5 gene revealed a single, heterozygous guanine to thymine (G → T) substitution at nucleotide position 470 (n.G470T), resulting in isoleucine (I) to serine (S) substitution at amino acid 157 (p.I157S). This mutation results in loss of ion selectivity, cell membrane depolarization, increased Ca2+ entry in adrenal glomerulosa cells, and increased aldosterone synthesis. Sequencing of the KCNK3, KCNK5, and KCNK9 genes revealed no mutations in our patients. Conclusions: These findings explain the pathogenesis in a subset of patients with severe hypertension and implicate loss of K+ channel selectivity in constitutive aldosterone production.


1987 ◽  
Author(s):  
S Terukina ◽  
M Matsuda ◽  
N Yoshida ◽  
K Yamazumi ◽  
Y Takeda ◽  
...  

A hitherto unidentified amino acid substitution of γ Arg-275 by Cys has been found in two abnormal fibrinogens, Osaka II and Morioka. The propositi are both asymptomatic heterozygotes for the abnormality characterized by altered polymerization of fibrin monomers. Reducing SDS-PAGE revealed that fibrinogens derived from thé propositi both consist of two populations; one with a normal and the other with an abnormal longer γ-chain by 0.5 Kd.The γ-γ cross-linking took place nearly normally, however. Analyzing plasmic digests of fibrinogen by SDS-PAGE, we located the abnormality residing in the γ-chain remnant of fragment D. Chromatofocusing of D1 obtained by plasmic digestion in 5 mM Ca++ of purified fibrinogen separated the variant D1 (vD1) from the normal one (nD1) distinctly, as confirmed by SDS-PAGE and functional studies. As anticipated, vD1 failed to interfere with normal fibrin polymerization and thrombin clotting of normal fibrinogen, whereas nD1 inhibited these reactions significantly. After reduction and pyridylethylation, vD1 and nD1 were individually digested with lysylendopeptidase (lysEP). Analyzing the digests by reverse phase HPLC, we noted a single peak present in the digests of vD1 but missing in those of nD1, and vice versa. Analysis of N-terminal five cycles of these peptides suggested that both of them corresponded to the peptide with residues 274302 based on the known sequence data. Primary sequence and total amino acid analyses revealed that γ Arg-275 has been substituted by Cys in both of these abnormal fibrinogens. Analysis of the lysEP-digests of the isolated γ-chain also gave the same result. Since no free SH has been identified at the γ Cys-275 substitute, the variant γ-chain may be endowed with some additive by an S-S linkage. Even if so, elucidation of an apparent elongation by SDS-PAGE of the γ-chain variant must await further investigation. In any case, however, the substitution of γ Arg-275 by Cys may have induced critical alterations in the γ-chain-dependent polymerization site in the D domain in these two abnormal fibrinogens.


Author(s):  
Renganayaki G. ◽  
Achuthsankar S. Nair

Sequence alignment algorithms and  database search methods use BLOSUM and PAM substitution matrices constructed from general proteins. These de facto matrices are not optimal to align sequences accurately, for the proteins with markedly different compositional bias in the amino acid.   In this work, a new amino acid substitution matrix is calculated for the disorder and low complexity rich region of Hub proteins, based on residue characteristics. Insights into the amino acid background frequencies and the substitution scores obtained from the Hubsm unveils the  residue substitution patterns which differs from commonly used scoring matrices .When comparing the Hub protein sequences for detecting homologs,  the use of this Hubsm matrix yields better results than PAM and BLOSUM matrices. Usage of Hubsm matrix can be optimal in database search and for the construction of more accurate sequence alignments of Hub proteins.


1996 ◽  
Vol 5 (3) ◽  
pp. 542-545 ◽  
Author(s):  
Kunihiko Gekko ◽  
Youjiro Tamura ◽  
Eiji Ohmae ◽  
Hideyuki Hayashi ◽  
Hiroyuki Kagamiyama ◽  
...  

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