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alpha-Adducin 460Trp allele is associated with erythrocyte Na transport rate in North Sardinian primary hypertensives.

Erythrocyte membrane alterations mirror those of vascular smooth muscle and renal tubular cell membrane. The interaction between adducin and Na-K pump is the most likely biochemical mechanism responsible for the increased tubular Na reabsorption and hypertension in Milan hypertensive strain (MHS) rats. To substantiate this hypothesis in humans, we tested to see if alpha-adducin Gly460Trp genotype is associated with erythrocyte sodium transport rate in a new cohort of n=268 never-treated North Sardinian primary hypertensives. Plasma renin activity and blood pressure response to hydrochlorothiazide were also measured to evaluate the relationship between sodium transport rate and two intermediate phenotypes with a higher degree of genetic complexity. Na-K pump, Na-K-Cl cotransport, and Li-Na countertransport at V(max) were faster (P<0.0001), whereas intracellular Na concentration was lower (P<0.0001) in patients carrying one or two 460Trp alleles. Such behavior was mirrored by opposite changes of intracellular Na concentration. Plasma renin activity and blood pressure response to diuretic treatment, on the other hand, showed a weaker association with the sodium transport rate. In conclusion, our findings are consistent with the hypothesis that the Gly460Trp alpha-adducin polymorphism may affect renal Na handling through an alteration in ion transport across the cell membrane mirrored by erythrocytes. These results may also have clinical relevance because the Gly460Trp alpha-adducin polymorphism may explain, at least in part, the variability of blood pressure response to diuretics in primary hypertensive patients.

Alleles↗

Low-renin hypertension, altered sodium homeostasis, and an alpha-adducin polymorphism.

Defining the genetic basis of common forms of human essential hypertension is most informative when correlated with physiological mechanisms that underlie blood pressure regulation. A polymorphism of the alpha-adducin gene as been associated with elevated blood pressure in the rat, but previous studies of the 460Trp polymorphism of the human alpha-adducin gene have not clearly identified an association with hypertension. In this study, the frequency of the 460Trp allele was 19% and 9 of 279 subjects (3.2%) were homozygous for the 460Trp allele. The systolic blood pressure response to changes in dietary sodium was significantly greater in subjects homozygous for the 460Trp allele (25 +/- 4 mm Hg) compared with subjects heterozygous for 460Trp (12 +/- 2 mm Hg) or homozygous for the 460Gly allele (14 +/- 1 mm Hg). Intracellular erythrocyte sodium content, sodium-lithium countertransport, and renal fractional excretion of sodium were significantly decreased in subjects homozygous for the 460Trp polymorphism (P<0.05). There was a significant association between homozygosity for the 460Trp allele and low-renin hypertension. Subjects heterozygous for the 460Trp allele did not have increased salt-sensitivity or an increased frequency of low-renin hypertension. Therefore, this study demonstrates a common genetic basis for altered cellular sodium homeostasis, impaired renal sodium handling, and salt-sensitivity of systolic blood pressure in individuals homozygous for the 460Trp polymorphism of the alpha-adducin gene. Homozygosity for this alpha-adducin allele may be an important determinant for approximately 10% of individuals with low-renin hypertension.

Adolescent↗

[Association of polymorphism in alpha-adducin gene with antihypertensive effect of Hydrochlorothiazide].

OBJECTIVE: To explore the association between G614T single nuclear polymorphism (SNP) of the alpha-adducin gene and the antihypertensive effect of hydrochlorothiazide (HCTZ) in essential hypertensive (EH) patients. METHODS: Eight hundred twenty nine EH patients were given 12.5 mg HCTZ/d for six weeks. Alpha-adducin gene G614T SNP in the tenth exon was determined by PCR-RFLP in 754 patients with complete records. All the patients were grouped according to TT, GT and GG genotypes. RESULTS: After 6 weeks of HCTZ treatment, the decreases in DBP and MAP of patients carrying 614T allele of alpha-adducin were significantly greater than that of those carrying GG homozygotes (P < 0.05). The decreases in SBP and MAP were significantly greater in patients with the TT genotype as compared with GT or GG genotype (P < 0.05). The effective rate of BP fall by HCTZ was higher in patients with TT genotype than those with GT or GG genotype (P < 0.05). Multivariate stepwise regression analysis showed that the TT genotype and the baseline SBP were the two major predictors affecting the decrease in SBP. CONCLUSION: The present study suggests that the alpha-adducin G614T polymorphism is associated with the antihypertensive effect of HCTZ, which is more effective in patients with TT genotype.

Adult↗

Role of Adducin-like (hu-li tai shao) mRNA and protein localization in regulating cytoskeletal structure and function during Drosophila Oogenesis and early embryogenesis.

Adducin is a cytoskeletal protein that can function in vitro to bundle F-actin and to control the assembly of the F-actin/spectrin cytoskeletal network. We previously reported cloning of the Drosophila Adducin-like (Add) locus [Ding et al., 1993] also referred to as hu-li tai shao (hts) [Yue and Spradling, 1992], and identification of two adducin-related protein isoforms: a 95 x 10(3) Mr form (ADD-95) and an 87 x 10(3) Mr form (ADD-87) [Zaccai and Lipshitz, 1996]. ADD-87 protein is present throughout the oocyte cortex at stages 9 and 10 of oogenesis but is restricted to its anterior pole from stage 11 onward. This ADD-87 protein localization is preceded by localization of Add-hts mRNA first to the cortex and then to the anterior pole of the oocyte. Mutation of the swallow gene results in delocalization of Add-hts mRNA and ADD-87 protein from the cortex of stage 9 and 10 oocytes, and from the anterior pole of later stage oocytes. Early embryos produced by swallow or Add-hts mutant females have severe defects in the distribution of F-actin and spectrin as well as abnormalities in nuclear division, nuclear migration, and cellularization. In addition to their cytoskeletal defects, embryos produced by swallow females have an abnormal anterior pattern because bicoid mRNA is delocalized from the anterior pole. In contrast, bicoid mRNA is still found at the anterior of embryos produced by Add-hts mothers. Thus swallow functions to restrict bicoid mRNA and Add-hts mRNA to the cortex of the oocyte. Cortical restriction of Add-hts mRNA and protein is required for the normal structure and function of the early embryonic F-actin/spectrin cytoskeleton. A defective embryonic cytoskeleton can be induced in either of two ways: (1) by delocalization of functional ADD from the oocyte cortex (as in swallow mutants), or (2) by reduction of ADD function while retaining its normal cortical localization during oogenesis (as in Add-hts mutants).

Actins↗

The mouse adducin gene family: alternative splicing and chromosomal localization.

Mouse cDNA sequences encoding alpha, beta, and gamma adducins were cloned from a mouse reticulocyte cDNA library. The purified clones contain alternatively spliced exons from all three adducin genes. In the case of alpha and beta, the inclusion of the alternatively spliced exons results in truncated polypeptide isoforms (called alpha-2 and beta-2). The mouse predicted amino acid sequences are compared with published rat and human sequences. For completion of this comparison, cDNA encoding the rat beta-1 carboxy terminus was cloned by PCR. The carboxy terminal region containing MARCKS homology, calmodulin-binding region-2, and spectrin-actin-binding site, is conserved among alpha-1, beta-1, and gamma-1 isoforms in mouse, rat, and humans. We also report here the localization of the gene encoding gamma adducin (Add3) to murine Chr 19, in a region that shows conserved synteny with human Chr 10.

Alternative Splicing↗

Alpha-adducin G460W polymorphism, urinary sodium excretion, and blood pressure in community-based samples.

BACKGROUND: There is limited evidence on the gene-environmental interaction among alpha-adducin G460W gene polymorphism, sodium intake, and blood pressure (BP) levels in a general population. One hypothesis is that the association between G460W polymorphism and BP is more evident among persons with higher sodium intake than those with lower sodium intake. METHODS: We conducted a population-based cross-sectional study of 2823 men and women aged 30 to 74 years in a Japanese rural community to examine the association of the alpha-adducin G460W polymorphism with BP levels stratified by salt intake, as estimated by 24-h urine collection and dietary questionnaire. RESULTS: There was no difference in systolic or diastolic BP levels among the GG, GW, and WW groups for women, but for men, mean systolic BP tended to be higher in the WW group than in the GG group. When we stratified men according to sodium excretion/intake, mean systolic BP was significantly higher in the WW group than in the GG group among men with higher urinary sodium excretion (138.8 v 133.6 mm Hg, P =.02) and tended to be higher among men with higher previous sodium intake. No genetic association was found among women or among men with lower urinary sodium excretion or lower sodium intake. CONCLUSIONS: The alpha-adducin WW genotype was associated with higher systolic BP among men with a higher sodium intake.

Adult↗

Expression analysis of the human adducin gene family and evidence of ADD2 beta4 multiple splicing variants.

Adducin is a cytoskeleton heterodimeric protein. Its subunits are encoded by three related genes (ADD1, ADD2, and ADD3) which show alternative spliced variants. Adducin polymorphisms are involved in blood pressure regulation in humans and rats. We have analyzed mRNA distribution of ADD gene family in human tissues and cells with Real-Time TaqMan RT-PCR. Whereas ADD1 is ubiquitously distributed, ADD3 is more expressed in kidney medulla and cortex than in fetal kidney, while in adult liver it is less abundant than in fetal liver. ADD2 beta1 and beta4 variants show the same pattern of distribution with the highest expression in brain, fetal liver, and kidney. Conventional RT-PCR identified new beta4 variants. Beta4a is characterized by an in-frame insertion of 21 nucleotides upstream exon 15 predicting a 7 amino acids longer protein with a similar C-terminus region. It is coexpressed with beta1 and beta4 in several tissues. Fetal kidney shows further beta4b, beta4c and beta4d variants containing internal exon deletions that enormously modify the predicted NH(2) and central regions. Our findings could help one to understand the functional role of adducin variants in specific tissues and cells.

Amino Acid Sequence↗

Expression of adducin genes during erythropoiesis: a novel erythroid promoter for ADD2.

OBJECTIVE: The first objective of this study was to examine the differences in levels of adducin (ADD1, ADD2, ADD3) mRNA expression during human erythropoiesis. The second objective was to determine whether the rapid induction of ADD2 expression could be attributed to a novel erythroid-specific promoter. METHODS: Expression of mRNA was quantified using real-time RT-PCR. Primary erythroid precursors were isolated from normal human bone marrow using fluorescence-activated cell sorting. Two model systems were compared: CD34(+) hematopoietic stem cells induced to differentiate with erythropoietin and HEL cells induced to differentiate with hemin. 5'RACE analysis was performed using primary human erythroblasts as starting material. RESULTS: All three adducin genes showed different patterns of expression during erythropoietic differentiation of cultured CD34(+) stem cells. Levels of ADD3 mRNA were higher than levels of ADD2 mRNA at early stages of erythropoiesis. Expression of ADD2 was induced to very high levels (100 times baseline) in erythropoietin-stimulated cultures. 5'RACE analysis identified a novel starting exon and putative erythroid promoter for ADD2. CONCLUSION: These results suggest that expression of each adducin gene is regulated in a gene-specific manner during erythropoiesis. The early expression of ADD3 suggests that it may have a role in erythroblasts but is replaced by ADD2 in later stages of erythropoiesis. The very high levels of expression of ADD2 suggest that its promoter may be useful for directing erythroid-specific gene expression.

Antigens, CD↗

Tissue-specific modulation of beta-adducin transcripts in Milan hypertensive rats.

Genetic variants in Adducins, a family of cytoskeleton proteins (alpha, beta, and gamma) encoded by three genes, have been associated with primary hypertension in humans and in Milan hypertensive (MHS) rats. The present paper describes the identification of a rat beta 4 alternative splicing isoform differing from beta subunit for an in-frame insertion of 18 amino acids and showing a polymorphic site (R592W) between MHS and its normotensive control (MNS). Furthermore, we established a quantitative real-time PCR assay for analyzing the tissue expression of adducin gene family and determining whether any subunit transcript demonstrates altered expression during the development of MHS hypertension, especially in tissues relevant for the control of cardiovascular phenotypes (i.e., kidney, left ventricle, and large arteries). Among the three adducins only beta transcripts were modulated, in a tissue-specific manner, during the development of hypertension in MHS, compared to age-matched MNS controls. A 43% decrease in renal outer medulla was already present at the prehypertensive phase; a 70% decrease in femoral artery and 66% increase in left ventricle were observed after the development of hypertension. Surprisingly beta 4-Add, which is a minor component of total beta transcripts, is drastically reduced up to 88% in all MHS tissues. Alteration in beta-Add expression levels may account, at least in part, for the observed phenotypic changes in MHS hypertension.

Alternative Splicing↗

Expression of gamma-adducin is associated with regions of morphogenetic cell movement in the chick embryo.

The adducin family of cytoskeletal proteins are known to mediate actin driven cell movements. Here we describe the cloning and expression pattern of a gene encoding gamma-adducin in the chick embryo. Expression of this gene is strikingly restricted to the epithelial cell layer (with a few exceptions including emerging notochord and lateral mesoderm). Gamma-adducin is detected at particularly high levels in cell populations undergoing important morphogenetic movements, such as epiblast approaching the primitive streak, regressing spinal cord primordia and closing neural tube.

Amino Acid Sequence↗

Cloning of the alpha-adducin gene from the Huntington's disease candidate region of chromosome 4 by exon amplification.

We have applied the technique of exon amplification to the isolation of genes from the chromosome 4p16.3 Huntington's disease (HD) candidate region. Exons recovered from cosmid Y24 identified cDNA clones corresponding to the alpha-subunit of adducin, a calmodulin-binding protein that is thought to promote assembly of spectrin-actin complexes in the formation of the membrane cytoskeleton, alpha-adducin is widely expressed and, at least in brain, is encoded by alternatively spliced mRNAs. The alpha-adducin gene maps immediately telomeric to D4S95, in a region likely to contain the HD defect, and must be scrutinized to establish whether it is the site of the HD mutation.

Alternative Splicing↗

The 460Trp polymorphism of the human alpha-adducin gene is not associated with isolated systolic hypertension in elderly Australian Caucasians.

The study was undertaken to determine whether polymorphic variants of the alpha-adducin gene are associated with isolated systolic hypertension (ISH) in elderly Australian Caucasians. Participants were classified with ISH (n = 87, systolic blood pressure (SBP) > or =160 mm Hg and diastolic blood pressure (DBP) < or =90 mm Hg) or normotension (n = 124, SBP <140 mm Hg and DBP <90 mm Hg with no family history of hypertension). To collect demographic data, a structured questionnaire was used. DNA was extracted using standard techniques from 211 subjects (age range 61-89, mean age 73 +/- 6.6 years, male: female ratio 1.1:1). Genotypes (gly/gly, trp/gly and trp/trp) were assigned in triplicate by polymerase chain reaction (PCR) followed by electrophoresis, using a laser scanning electrophoresis unit. The validity of the method was confirmed by sequencing. Frequencies of allele distribution in ISH or control groups were determined by Chi-square tests and a stepwise logistic regression model, which controlled for potential confounders, was used to examine any independent association between alpha-adducin genotypes or alleles with ISH and normotensive controls. Mean BP (+/- s.d.) was: 170/79.8 +/- 14.9/8.3 mm Hg and 122.1/ 73.4 +/- 8. 8/7.6 mm Hg in the ISH and normotension groups respectively. The unadjusted allele and genotypes frequencies were not significantly different in the ISH patients groups compared with normotensive controls (chi2 = 1.59, P = 0.45 and chi2 = 1.23, P = 0.28 respectively). In this elderly cohort, after adjustment for potential confounders, no statistically significant association was found between alpha-adducin genotype and SBP (P = 0.65 for homozygotes, P = 0.59, for heterozygotes), DBP (P = 0.49 homozygotes, for heterozygotes P = 0.45) pulse pressure (P = 0.87 homozygotes, for heterozygotes P = 0.95) diagnosis of ISH (P = 0.72 for homozygotes, P = 0.68 for heterozygotes). However age and renal disease predicted the diagnosis of ISH (P = 0.001, P = 0.459, respectively), a large pulse pressure (P < 0.0001, P = 0.033, respectively) and a higher SBP (P < 0.0001, P = 0.025, respectively) in this large cohort of elderly Australian Caucasian volunteers. Journal of Human Hypertension (2000) 14, 199-203.

Aged↗

Ganglioside-induced adherence of botulinum and tetanus neurotoxins to adducin.

Preincubation of botulinum neurotoxin serotype A, B, or E with ganglioside GT1b was previously found to enhance adherence of botulinum neurotoxin to synapsin I and an approximately 116-kDa bovine brain synaptosomal protein; in contrast, adherence to these two proteins by tetanus neurotoxin required preincubation with GT1b. We have now found that preincubation of the neurotoxins with ganglioside GD3 enhances their adherence to the approximately 116-kDa protein more than that with GT1b. A purified preparation of the water-soluble approximately 116-kDa protein was obtained from bovine brain synaptosomes by preparative column sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. N-Terminal amino acid sequences were obtained for two tryptic fragments of the approximately 116-kDa protein. These sequences matched with the data bank sequences for beta-adducin, a cytoskeletal protein. The carboxy-terminal tail region of adducin, but not the head region, was adhered to by the neurotoxins. Adherence of the neurotoxin to adducin and synapsin I may facilitate presentation of the neurotoxin to its specific substrate(s).

Amino Acid Sequence↗

Combined deletion of mouse dematin-headpiece and beta-adducin exerts a novel effect on the spectrin-actin junctions leading to erythrocyte fragility and hemolytic anemia.

Dematin and adducin are actin-binding proteins of the erythrocyte "junctional complex." Individually, they exert modest effects on erythrocyte shape and membrane stability, and their homologues are expressed widely in non-erythroid cells. Here we report generation and characterization of double knock-out mice lacking beta-adducin and the headpiece domain of dematin. The combined mutations result in altered erythrocyte morphology, increased membrane instability, and severe hemolysis. Peripheral blood analysis shows evidence of severe hemolytic anemia with reduced number of erythrocytes/hematocrit/hemoglobin and an approximately 12-fold increase in the number of circulating reticulocytes. The presence of a variety of misshapen and fragmented erythrocytes correlates with increased osmotic fragility and reduced in vivo life span. Despite the apparently normal protein composition of the mutant erythrocyte membrane, the retention of the spectrin-actin complex in the membrane under low ionic strength conditions is significantly reduced by the double mutation. Atomic force microscopy reveals an increase in grain size and a decrease in filament number of the mutant membrane cytoskeleton, although the volume parameter is similar to wild type erythrocytes. Aggregated, disassembled, and irregular features are visualized in the mutant membrane, consistent with the presence of large protein aggregates. Importantly, purified dematin binds to the stripped inside-out vesicles in a saturable manner, and dematin-membrane binding is abolished upon pretreatment of membrane vesicles with trypsin. Together, these results reveal an essential role of dematin and adducin in the maintenance of erythrocyte shape and membrane stability, and they suggest that the dematin-membrane interaction could link the junctional complex to the plasma membrane in erythroid cells.

Actins↗

Role of the adducin family genes in human essential hypertension.

OBJECTIVE: In both humans and rats, polymorphisms of the alpha adducin (ADD1) gene are involved in renal sodium handling, essential hypertension and some of its organ complications. Adducin functions within cells as a heterodimer composed of various combinations of three subunits that are coded by three genes (ADD1, 2, 3) each located on a different chromosome. DESIGN: These characteristics provide the biochemical basis for investigating epistatic interactions among these loci. METHODS: We examined the three adducin gene polymorphisms and their association with ambulatory blood pressure (ABPM) and with plasma levels of renin activity (PRA), endogenous ouabain (EO), in 512 newly discovered and never-treated hypertensive patients. RESULTS: Relative to carriers of the wild type (Gly/Gly) ADD1 gene, patients carrying the mutated Trp ADD1 allele had higher blood pressure (systolic blood pressure (SBP) 143.2 +/- 1.0 versus 140.6 +/- 0.6 mmHg P = 0.027 and diastolic blood pressure (DBP) 94.2 +/- 0.77 versus 92.3 +/- 0.5 mmHg, P = 0.03), lower PRA and EO, consistent with the hypothesis of the renal sodium retaining effect of the Trp allele. Polymorphisms in the ADD2 and ADD3 genes taken alone were not associated with these variables. However, the differences in SBP and DBP between the two ADD1 genotypes were greatest in carriers of the ADD3 G allele (around + 8 mmHg). The significance of the interaction between ADD1 and ADD3 ranged between P = 0.020 to P = 0.006 according to the genetic model applied. CONCLUSIONS: The interaction of ADD1 and ADD3 gene variants in humans is statistically associated with variation in blood pressure, suggesting the presence of epistatic effects among these loci.

Adult↗

A new antihypertensive agent that antagonizes the prohypertensive effect of endogenous ouabain and adducin.

Endogenous Ouabain (EO) and Adducin enhance the Na-K pump function and play an important role in sodium homeostasis and blood pressure (BP) regulation. In the general population, plasma EO modulates BP either by inhibiting the prohypertensive effect of an excessive salt intake or counteracting the depressor action of normal-moderate salt intake. Almost 50% of hypertensive patients have increased circulating plasma levels of EO. EO has been associated both to left ventricular dysfunction and hypertrophy. A new antihypertensive agent, PST2238, (17beta-(3-furyl)-5beta-androstan-3beta, 14beta, 17alpha-triol a digitoxigenin derivative) able to selectively antagonize both the EO and adducin prohypertensive and molecular effects, has been developed. In hypertensive rats (MHS strain) carrying both adducin mutations and increased plasma EO and in ouabain-infused rats (OS), PST2238 lowers BP by normalizing the renal Na-K pump function. In OS rats, PST antagonized the cardiac and renal pro-hypertrophic ouabain effect associated to the activation of the Src-EGFr-ERK(1/2) signaling cascade. Phase 1 clinical studies demonstrated a high tolerability of PST2238. In a preliminary phase 2 study on 42 mild never-treated hypertensive patients, PST2238 given for 3 months at 0.5 mg/day, significantly reduced BP in subjects with moderate salt intake, implying that it may be selectively effective in conditions where EO plays a prohypertensive role. In conclusion, PST2238, because of its peculiar action mechanism, represents a new tool to disentangle the complex relationship between salt intake, genetic control of renal sodium handling and EO effect.

Androstanols↗

Significant associations of the alpha-adducin gene Gly460Trp polymorphism with serum bilirubin concentrations in Chinese essential hypertension patients.

We investigated associations of the Gly460Trp polymorphism of the alpha-adducin gene and concentrations of serum total bilirubin, serum direct bilirubin and serum unconjugated bilirubin in patients with essential hypertension from Anhui, China from September 2000 to January 2001. Compared to women with the Gly/Gly genotype and after adjustment for important covariates, women with the Trp/Trp genotype had lower mean concentrations of serum total bilirubin (beta = -1.2 micromol/L; P = 0.01), serum direct bilirubin (beta = - 0.4 micromol/L; P = 0.02) and serum unconjugated bilirubin (P = -0.8 micromol/L; P = 0.03). Among women in either the upper or lower quartiles of serum total bilirubin, serum direct bilirubin and serum unconjugated bilirubin and compared to those with the Gly/Gly genotype, women with the Trp/Trp genotype had higher odds of being in the lower quartile of concentrations of serum total bilirubin (odds ratio = 4.0; 95 percent confidence interval: 1.6 - 10.2; P < 0.01), serum direct bilirubin (odds ratio = 4.0; 95 percent confidence: 1.6 - 9.7; P < 0.01) and serum unconjugated bilirubin (odds ratio = 2.7; 95 percent confidence interval: 1.1 - 6.7; P = 0.03) after adjustment for important covariates. We did not observe any significant associations in these models for men. We concluded that the Trp/Trp genotype of alpha-adducin Gly460Trp was associated with lower serum bilirubin concentrations in this group of Chinese women with essential hypertension. Women with the Trp/Trp genotype of alpha-adducin Gly460Trp might have increased risk for cardiovascular diseases due to lower concentrations of serum bilirubin.

Adult↗

Expression of gamma-adducin is associated with regions of morphogenetic cell movement in the chick embryo.

The adducin family of cytoskeletal proteins are known to mediate actin driven cell movements. Here we describe the cloning and expression pattern of a gene encoding gamma-adducin in the chick embryo. Expression of this gene is strikingly restricted to the epithelial cell layer (with a few exceptions including emerging notochord and lateral mesoderm). Gamma-adducin is detected at particularly high levels in cell populations undergoing important morphogenetic movements, such as epiblast approaching the primitive streak, regressing spinal cord primordia and closing neural tube.

Animals↗