Cell age-related monovalent cations content and density changes in stored human erythrocytes

Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a non-enzymatic deamidation reaction in most mammalian erythrocytes, with an in vivo half-life of approximately 41 days, making the 4.1a/4.1b ratio a useful index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988) 256-264]. Normal human erythrocytes distribute into subpopulations of increasing cell density and cell age when centrifuged in polyarabinogalactan density gradients. We have observed that, when erythrocytes were stored at 4 degrees C under standard blood bank conditions, the deamidation was virtually undetectable, as cells maintained the 4.1a/4.1b ratio they displayed at the onset of storage. By measuring the 4.1a/4.1b values in subpopulations of cells of different density at various time points during storage, a modification of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent manner. This may stem from a different impact of storage on the imbalance of monovalent cations, Na(+) and K(+), in young and old erythrocytes, related to their different complement of cation transporters.     

Successful shape-based virtual screening: the discovery of a potent inhibitor of the type I TGFbeta receptor kinase (TbetaRI)

We describe the discovery, using shape-based virtual screening, of a potent, ATP site-directed inhibitor of the TβRI kinase, an important and novel drug target for fibrosis and cancer. The first detailed report of a TβRI kinase small molecule co-complex confirms the predicted binding interactions of our small molecule inhibitor, which stabilizes the inactive kinase conformation. Our results validate shape-based screening as a powerful tool to discover useful leads against a new drug target.     

Inhibition of hypothalamic carnitine palmitoyltransferase-1 decreases food intake and glucose production

The enzyme carnitine palmitoyltransferase-1 (CPT1) regulates long-chain fatty acid (LCFA) entry into mitochondria, where the LCFAs undergo beta-oxidation. To investigate the mechanism(s) by which central metabolism of lipids can modulate energy balance, we selectively reduced lipid oxidation in the hypothalamus. We decreased the activity of CPT1 by administering to rats a ribozyme-containing plasmid designed specifically to decrease the expression of this enzyme or by infusing pharmacological inhibitors of its activity into the third cerebral ventricle. Either genetic or biochemical inhibition of hypothalamic CPT1 activity was sufficient to substantially diminish food intake and endogenous glucose production. These results indicated that changes in the rate of lipid oxidation in selective hypothalamic neurons signaled nutrient availability to the hypothalamus, which in turn modulated the exogenous and endogenous inputs of nutrients into the circulation.     

Specific antibody promotes opsonization and PMN-mediated killing of phagocytosis-resistant Enterococcus faecium

Many clinical isolates of Enterococcus faecium are resistant to neutrophil (PMN)-mediated phagocytosis and killing in the presence of normal human serum. We have now examined the ability of specific polyclonal rabbit antibodies to promote opsonization and killing of phagocytosis-resistant E. faecium. Immune rabbit serum generated against formalin-killed E. faecium TX0016, a phagocytosis-resistant strain, markedly promoted binding of TX0016 organisms to PMNs and PMN-mediated killing. These effects were dramatically reduced by (a) adsorption of immune serum with E. faecium TX0016, but not by adsorption with a strain of E. faecium susceptible to phagocytosis, and (b) incubation of immune serum with carbohydrate purified from TX0016, but not by incubation with a surface protein extract from TX0016. IgG purified from immune serum was unable by itself to promote bacterial binding to PMNs. However, specific IgG was able to promote binding to PMNs and PMN-mediated killing in the presence of normal human serum as a complement source, as were F(ab')(2) and Fab fragments produced from it, and the alternative pathway of complement was sufficient to promote IgG- and F(ab')(2)-mediated opsonization. PMN complement receptor type 3, but not complement receptor type 1, was involved in bacterial binding to PMNs induced by the combination of F(ab')(2) fragments and normal human serum. These results suggest that opsonization by antibodies potentially directed against bacterial carbohydrate, in conjunction with complement activation, has an important role in the host defense against phagocytosis-resistant E. faecium.     

Genetic heterogeneity, reproductive isolation and host preferences in mealy aphids of the Hyalopterus pruni complex (Homoptera, Aphidoidea)

Three taxa were detected by allozyme markers within the mealy aphids of the Hyalopterus pruni complex, having different cultivated Prunus species as main primary hosts. The genetically closer H. pruni and H. amygdali A ( D _Nei= 0.10) never share primary hosts, whereas H. amygdali A and B ( D _Nei= 0.32) may occasionally share them, producing few F₁ hybrids. The three species proved reproductively isolated in the field, with no gene exchange. Their speciation seem to have occurred long before the agricultural revolution, crop colonization representing a host range expansion rather than a host shift, as in sympatric speciation.     

Characterization and Subcellular Localization of l-[3H]Carnitine Binding Sites in Rat Brain

Abstract: In the present study, we investigated the existence of a binding site for l -carnitine in the rat brain. In crude synaptic membranes, l -[³H]carnitine bound with relatively high affinity (K_D = 281 nM) and in a saturable manner to a finite number (apparent B_max value = 7.3 pmol/mg of protein) of binding sites. Binding was reversible and dependent on protein concentration, pH, ionic strength, and temperature. Kinetic studies revealed a K_off of 0.018 min^?1 and a K_on of 0.187 × 10^?3 min^?1 nM^?1. Binding was highest in spinal cord, followed by medulla oblongata-pons ≥ corpus striatum ≥ cerebellum = cerebral cortex = hippocampus = hypothalamus = olfactory bulb. l -[³H]Carnitine binding was stereoselective for the l -isomers of carnitine, propionylcarnitine, and acetylcarnitine. The most potent inhibitor of l -[³H]carnitine binding was l -carnitine followed by propionyl-l -carnitine. Acetyl-l -carnitine and isobutyryl-l -carnitine showed an affinity ～500-fold lower than that obtained for l -carnitine. The precursor γ-butyrobetaine had negligible activity at 0.1 mM. l -Carnitine binding to rat crude synaptic membrane preparation was not inhibited by neurotransmitters (GABA, glycine, glutamate, aspartate, acetylcholine, dopamine, norepinephrine, epinephrine, 5-hydroxytryptamine, histamine) at a final concentration of 0.1 mM. In addition, the binding of these neuroactive compounds to their receptors was not influenced by the presence of 0.1 mMl -carnitine. Finally, a subcellular fractionation study showed that synaptic vesicles contained the highest density of l -carnitine membrane binding sites whereas l -carnitine palmitoyltransferase activity was undetectable, thus excluding the possibility of the presence of an active site for carnitine palmitoyltransferase. This finding indicated that the localization of the l -[³H]carnitine binding site should be essentially presynaptic.     

Primary structure of the major glycan from human seminal transferrin

Human seminal transferrin (HSmT) is an iron-containing glycoprotein whose structural properties have not been adequately investigated. The carbohydrate content of the purified glycoprotein amount to 6.1%, and monosaccharide analysis revealed the major oligosaccharide moiety to be of the N-glycoside type. The carbohydrate chains were released from the iron-free form by digestion with peptide N-glycosidase F (PNGase F) in the presence of detergents such as SDS and-octylglucoside. After ethanol precipitation and fractionation on Bio-Gel P-6 and Bio-Gel P-2, the oligosaccharide was further purified on Mono-Q and desalted on Bio-Gel P-2. By 600-MHz¹H-NMR spectroscopy, the primary structure of the major N-linked oligosaccharide component was established to be: Abbreviations used HSmT human seminal transferrin - HSrT human serum transferrin - PNGase F peptide-N⁴-(N-acetyl--glucosaminyl)asparagine amidase-F (E.C. 3.5.1.52), commonly known as peptide N-glycosidase F - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - GLC gas-liquid chromatography - FPLC fast liquid protein chromatography - EDTA ethylenediaminetetraacetic acid, disodium salt - PMFS phenylmethylsulfonyl fluoride - GlcNAc N-acetylglucosamine - NeuAc N-acetylneuraminic acid - Man, Gal galactose - Fuc fucose     

NPGB-induced inhibition of superoxide anion production by normal Lewis rat macrophages

The treatment of Lewis rat peritoneal macrophages with p¹-nitrophenyl p-guanidinobenzoate (NPGB) inhibited the superoxide anion production stimulated with phorbol myristate acetate (PMA). The addition of NPGB at the time of maximum superoxide generation was still able to block the superoxide release. It appears from these findings that NPGB may block either the activation process of the membrane bound NAD(P)H oxidase or directly on the active enzyme. Other protease inhibitors such as, epsilon-amino caproic acid (EACA), pepstatin, trans aminomethyl cyclohexane carboxylic acid (AMCA), aprotinin, and leupeptin did not inhibit the superoxide release. The superoxide anion release by the xanthine-xanthine oxidase system was not inhibited by NPGB. This finding indicates that NPGB does not itself react with superoxide. It has been also demonstrated that NPGB is a good reactant toward sulfhydryl group. The relevance of these finding to experimental allergic encephalomyelitis (EAE) is discussed.     

Effect of oxidative stress on membrane phospholipid and protein organization in human erythrocytes

Membrane phospholipid and protein organization was studied in intact human erythrocytes exposed to phenylhydrazine, an oxidative agent inducer. The evaluation of the membrane phospholipid and protein organization was carried out in terms of asymmetric distribution across the membrane bilayer for the phospholipids, and in terms of accessibility of cleavable sites present on the outer membrane surface for the proteins. Treatment of phenylhydrazine-exposed erythrocytes either with bee venom phospholipase A2 or with trinitrobenzenesulfonic acid indicated that phosphatidylserine (PS), which is the only phospholipid not formally present on the outer leaflet of the membrane, was translocated to the outer surface of the cell membrane. The extent of this phenomenon was directly proportional to the concentration of the oxidant having a peak value at 0.1 mM. Phosphatidylcholine and phosphatidylethanolamine conserved their original distribution across the erythrocyte membrane throughout the study. The oxidant, at a dose which did not induce any modification of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis cytoskeleton membrane protein pattern, did not provoke any alteration of the membrane protein surface architecture, although the translocation of PS to the membrane outer leaflet in intact erythrocytes was present.     

Crystal structure of myoglobin form a synthetic gene

Crystal have been grown of myoglobin produced in Escherichia coli from a synthetic gene, and the structure has been solved to 1.9 Å resolution. The space group of the crystals is P6, which is different from previously solved myoglobin crystal forms. The synthetic myoglobin is essentially identical to myoglobin isolated from sperm whale tissue, except for the retention of the initiator methionine at the N-terminus and the substitution of asparagine for aspartic acid at position 122. Superposition of the coordinates of native and synthetic sperm whale myoglobins reveals only minor changes in the positions of main chain atoms and roeientation of some surface side chains. Crystals of variant of the “synthetic” myoglobin have also been grown for structural analysis of the role of key amino acid residues in ligand and specificity.