Congestive heart failure: a case of protein misfolding.

This article describes an interesting case of a patient presenting with congestive heart failure found to have restrictive cardiomyopathy with initial laboratory evaluation showing hypogammaglobuminemia without a monoclonal band on serum and urine electrophoresis. This case highlights the clinically significant cardiac manifestation caused by protein misfolding, a defect in protein homeostasis. In addition, the utility of a relatively newer laboratory test, serum free light chains as well as the importance of clinical and pathophysiologic correlation is also discussed.

Novel insights into the pleiotropic effects of human serum albumin in health and disease.

Background: Human serum albumin is the principal protein in human serum. It participates in regulation of plasma oncotic pressure and transports endogenous and exogenous ligands such as thyroxine, free fatty acids, bilirubin, and various drugs. Therefore, studying its ligand binding mechanism is important in understanding many functions of the protein.

Histidine146 of human serum albumin plays a prominent role at the interface of subdomains IA and IIA in allosteric ligand binding.

Fatty acids are endogenous ligands of human serum albumin (HSA) that induce conformational changes and participate in allosteric ligand binding to HSA. In a previous study, we showed that, when myristate (MYR) is present, the binding of [(14) C]ketoprofen (KP) to subdomain IA of HSA was increased, indicating that, when MYR binds to HSA, a new binding site in formed in that region. Meanwhile, an N-B transition has been reported to increase the binding of ligands at alkaline pH when the status of albumin is the B-conformer.

Redox-sensitivity and site-specificity of S- and N- denitrosation in proteins.

Background: S-nitrosation--the formation of S-nitrosothiols (RSNOs) at cysteine residues in proteins--is a posttranslational modification involved in signal transduction and nitric oxide (NO) transport. Recent studies would also suggest the formation of N-nitrosamines (RNNOs) in proteins in vivo, although their biological significance remains obscure. In this study, we characterized a redox-based mechanism by which N-nitroso-tryptophan residues in proteins may be denitrosated.

A neonatal death due to medium-chain acyl-CoA dehydrogenase deficiency: utilization of the neonatal metabolic screen in a functional approach to sudden unexplained infant death.

We report a perinatal death due to medium-chain acyl-CoA dehydrogenase deficiency, which was referred to the Coroner's Physician as sudden unexplained infant death. Detailed death investigation including the autopsy findings, and newborn biochemical and molecular studies revealed the cause and natural manner of death. This disorder affects fatty acid oxidation and results in decreased tolerance for fasting, which can be life threatening.

Effects of statins on the secretion of human serum albumin in cultured HepG2 cells.

Statins reduce cholesterol biosynthesis by inhibiting HMG-CoA reductase and thereby lower total cholesterol and LDL cholesterol levels in serum, which in turn lower the incidence of cardiovascular disease (CVD). Statins are also known to modulate various cellular functions such as gene expression, cell proliferation, and programmed cell death through inhibition of downstream intermediates in cholesterol synthesis. In this study, we have investigated the possible effects of statins on the secretion of serum albumin from cultured HepG2 cells since high levels of serum albumin are associated with reduced risks for CVD and statins are effective in lowering the risk of CVD through other effects in addition to their effects on serum total cholesterol and LDL cholesterol levels, known as pleiotropic effects.

Human serum albumin levels and cardiovascular risk factors in elderly Japanese-American men: the Honolulu Heart Program.

The objective of this study is to investigate the relationship between lowlevels of human serum albumin (HSA) and the incidence of coronary heart disease (CHD) in a cohort of elderly Japanese-American men. Using data from the Honolulu Heart Program's fourth examination (1991-1993), HSA levels of 998 Japanese American men aged 71-93 years was compared with plasma levels of fibrinogen, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, diastolic BP, BMI, and fasting blood glucose. HSA was significantly negatively associated with age and fibrinogen, and significantly positively associated with total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, diastolic BP, BMI and fasting blood glucose.

Fatty acids bound to human serum albumin and its structural variants modulate apolipoprotein B secretion in HepG2 cells.

Epidemiologic studies have shown an inverse relationship between human serum albumin (HSA) levels and coronary heart disease (CHD). However, no mechanisms have been identified to explain this relationship. We hypothesized that this relationship is due to differences in binding affinity of fatty acids to HSA and subsequent atherogenic lipoprotein synthesis and secretion from hepatocytes.

Site-directed mutagenesis study of the role of histidine residues in the neutral-to-basic transition of human serum albumin.

Site-directed mutagenesis was used to study the role of histidine residues located in domain I in the neutral-to-basic (N-B) transition of human serum albumin (HSA). Based on a previous study of the N-B transition by means of proton NMR, the following recombinant HSA species were synthesized in the yeast species, Pichia pastoris: H9F, H9S, H39F, H39S, H67F, H67S, H105F, H105S, H128F, H128S, H146F, H146S, and wild type HSA. By monitoring the fluorescent intensity of warfarin bound to the above recombinant human serum albumin species as a function of pH, the mutational effect of individual histidine residues on the N-B transition was examined.

Insulinoma, a rare neuroendocrine tumor: a case report.

We report a case of Insulinoma, a rare neuroendocrine tumor with an incidence of approximately four per 5 million. This case demonstrates the characteristic clinical, biochemical and histological features of an insulinoma, a rare benign neuroendocrine tumor where early recognition is important to ensure proper surgical treatment and prevent serious adverse consequences.

Truncated human serum albumin retains general anaesthetic binding activity.

Multiple binding sites for anaesthetics in HSA (human serum albumin) make solution studies difficult to interpret. In the present study, we expressed the wild-type HSA domain 3 (wtHSAd3), a peptide with two known anaesthetic binding sites in a yeast expression system. We also expressed a site-directed mutant of domain 3 (Y411Wd3).

Analysis of tryptophan fluorescence lifetimes in a series of human serum albumin mutants with substitutions in subdomain 2A.

Tryptophan 214, the only tryptophan residue in human serum albumin, is located in the physiologically important subdomain 2A ligand binding site. In the present study the fluorescence lifetime of tryptophan 214 in the following human serum albumin (HSA) mutants with substitutions in subdomain 2A were determined: K195M, K199M, F211V, R218M, R218H, R218A, R222M, H242V, and R257M. An HSA mutant in which tryptophan was moved from subdomain 2A to subdomain 3A (W214L/Y411W) was also examined.

Comparative binding character of two general anaesthetics for sites on human serum albumin.

Propofol and halothane are clinically used general anaesthetics, which are transported primarily by HSA (human serum albumin) in the blood. Binding characteristics are therefore of interest for both the pharmacokinetics and pharmacodynamics of these drugs. We characterized anaesthetic-HSA interactions in solution using elution chromatography, ITC (isothermal titration calorimetry), hydrogen-exchange experiments and geometric analyses of high-resolution structures.

Structural basis of albumin-thyroxine interactions and familial dysalbuminemic hyperthyroxinemia.

Human serum albumin (HSA) is the major protein component of blood plasma and serves as a transporter for thyroxine and other hydrophobic compounds such as fatty acids and bilirubin. We report here a structural characterization of HSA-thyroxine interactions. Using crystallographic analyses we have identified four binding sites for thyroxine on HSA distributed in subdomains IIA, IIIA, and IIIB.

Human serum albumin and its structural variants mediate cholesterol efflux from cultured endothelial cells.

In the present study, we used the human EA.hy926 endothelial cell line as the model system to investigate the effect of human serum albumin (HSA) and its structural variants on cholesterol efflux. Initial studies showed that HSA promoted cholesterol efflux in a dose- and time-dependent manner, reaching a plateau at 10 mg/ml at 90 min.

Evaluation of human serum albumin cobalt binding assay for the assessment of myocardial ischemia and myocardial infarction.

Background: Clinical diagnoses were correlated with results of a Co(II)-albumin binding assay in 167 patients treated at an emergency department of a health maintenance organization.

Methods: Patients were evaluated as being nonischemic or potentially ischemic through standard coronary disease indicators [creatine kinase (CK), CK-MB, cardiac troponin I, and electrocardiographic findings] and were tested by a Co(II)-albumin binding assay. Samples were tested anonymously, and the study was double-blinded.

The role of electrostatic interactions in human serum albumin binding and stabilization by halothane.

Electrostatic interactions have been proposed as a potentially important force for anesthetics and protein binding but have not yet been tested directly. In the present study, we used wild-type human serum albumin (HSA) and specific site-directed mutants as a native protein model to investigate the role of electrostatic interactions in halothane binding. Structural geometry analysis of the HSA-halothane complex predicted an absence of significant electrostatic interactions, and direct binding (tryptophan fluorescence and zonal elution chromatography) and stability experiments (hydrogen exchange) confirmed that loss of charge in the binding sites, by charged to uncharged mutations and by changing ionic strength of the buffer, generally increased both regional (tryptophan region) and global halothane/HSA affinity.

Probing the structure of the warfarin-binding site on human serum albumin using site-directed mutagenesis.

The binding of warfarin to the following human serum albumin (HSA) mutants was examined: K195M, K199M, F211V, W214L, R218M, R222M, H242V, and R257M. Warfarin bound to human serum albumin (HSA) exhibits an intrinsic fluorescence that is approximately 10-fold greater than the corresponding signal for warfarin in aqueous solution. This property of the warfarin/HSA complex has been widely used to determine the dissociation constant for the interaction.

Cellular oxidant stress and advanced glycation endproducts of albumin: caveats of the dichlorofluorescein assay.

In order to understand the mechanism by which advanced glycation endproducts (AGEs) elicit oxidative stress, macrophage-like RAW264.7 cells were exposed to various AGE-albumins, and oxidant stress was estimated from the fluorescence of oxidized dichlorofluorescein using the microtiter plate assay. Strongest fluorescence was observed with methylglyoxal modified albumin (MGO-BSA) compared with native albumin.

Structural insights into human serum albumin-mediated prostaglandin catalysis.

Previous studies have shown that many arachidonic acid metabolites bind to human serum albumin (HSA) and that the metabolism of these molecules is altered as a result of binding. The present study attempted to gain insights into the mechanisms by which prostaglandins bound to subdomain 2A of HSA are metabolized by catalytic processes. The breakdown of the prostaglandin 15-keto-PGE(2) to 15-keto-PGA(2) and 15-keto-PGB(2) in the presence of wild-type HSA and a number of subdomain 2A mutants was examined using a previously validated spectroscopic method which monitors absorbance at 505 nm.

Site-directed mutagenesis studies of human serum albumin define tryptophan at amino acid position 214 as the principal site for nitrosation.

The patterns of nitric oxide (NO) release from nitrosated bovine serum albumin (BSA), human serum albumin (HSA) and a number of recombinant HSA mutants were compared. All albumin species were nitrosated by incubation with acidified NO(2)(-). The pattern of NO release from BSA nitrosated with acidified NO(2)(-) was in agreement with previous reports which indicated that Cys-34 is the primary target for nitrosation in BSA.