Roles of different peptide fragments derived from proadrenomedullin in the regulation of vascular tone in isolated rat aorta

The effects of proadrenomedullin N-terminal 20 peptide (PAMP) and adrenotensin (ADT) on adrenomedullin (ADM)-induced vasodilation were investigated in aortic rings from rat. ADM (10(-9) to 10(-7)M) relaxed the aorta preconstricted with phenylephrine in a concentration-dependent manner. Denudation of endothelium or pretreatment with nitric oxide synthase (NOS) inhibitor, L-NAME, attenuated the vasodilatory action of ADM. ADM-induced vasorelaxation in the aortic rings with endothelium was converted to contraction by PAMP, but not by ADT. The ADM-induced vasodilation was not affected by PAMP in aorta rings without endothelium or in intact aortic rings pretreated with L-NAME. ADM-stimulated nitrite production and NOS activity of the aortas, which was inhibited by PAMP, ADT or PAMP plus ADT. ADM, PAMP, and ADT increased the cyclic adenosine monophosphate (cAMP) contents in vascular tissue. The combination of ADM with PAMP or ADT caused a smaller increase in cAMP level as compared with that of PAMP or ADT alone. These results show that ADM-induced endothelium-dependent vasodilation could be converted to vasoconstriction in the presence of PAMP, probably through a NO-dependent pathway. There was no indication that cAMP was involved in the converting effect of PAMP on ADM vasodilator action.     

Substrate binding and catalysis in trichosanthin occur in different sites as revealed by the complex structures of several E85 mutants

Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) which possesses rRNA N-glycosidase activity. In recent years, its immunomodulatory, anti-tumor and anti-HIV properties have been revealed. Here we report the crystal structures of several E85 mutant TCS complexes with adenosine-5'-monophosphate (AMP) and adenine. In E85Q TCS/AMP and E85A TCS/AMP, near the active site of the molecule and parallel to the aromatic ring of Tyr70, an AMP molecule is bound to the mutant without being hydrolyzed. In the E85R TCS/adenine complex, the hydrolyzed product adenine is located in the active pocket where it occupies a position similar to that in the TCS/NADPH complex. Significantly, AMP is bound in a position different to that of adenine. In comparison with these structures, we suggest that there are at least two subsites in the active site of TCS, one for initial substrate recognition as revealed by the AMP site and another for catalysis as represented by the NADPH site. Based on these complex structures, the function of residue 85 and the mechanism of catalysis are proposed.     

PROSPECT II: protein structure prediction program for genome-scale applications

A new method for fold recognition is developed and added to the general protein structure prediction package PROSPECT (http://compbio.ornl.gov/PROSPECT/). The new method (PROSPECT II) has four key features. (i) We have developed an efficient way to utilize the evolutionary information for evaluating the threading potentials including singleton and pairwise energies. (ii) We have developed a two-stage threading strategy: (a) threading using dynamic programming without considering the pairwise energy and (b) fold recognition considering all the energy terms, including the pairwise energy calculated from the dynamic programming threading alignments. (iii) We have developed a combined z-score scheme for fold recognition, which takes into consideration the z-scores of each energy term. (iv) Based on the z-scores, we have developed a confidence index, which measures the reliability of a prediction and a possible structure-function relationship based on a statistical analysis of a large data set consisting of threadings of 600 query proteins against the entire FSSP templates. Tests on several benchmark sets indicate that the evolutionary information and other new features of PROSPECT II greatly improve the alignment accuracy. We also demonstrate that the performance of PROSPECT II on fold recognition is significantly better than any other method available at all levels of similarity. Improvement in the sensitivity of the fold recognition, especially at the superfamily and fold levels, makes PROSPECT II a reliable and fully automated protein structure and function prediction program for genome-scale applications.     

Role of ALDP (ABCD1) and mitochondria in X-linked adrenoleukodystrophy

Peroxisomal disorders have been associated with malfunction of peroxisomal metabolic pathways, but the pathogenesis of these disorders is largely unknown. X-linked adrenoleukodystrophy (X-ALD) is associated with elevated levels of very-long-chain fatty acids (VLCFA; C(>22:0)) that have been attributed to reduced peroxisomal VLCFA beta-oxidation activity. Previously, our laboratory and others have reported elevated VLCFA levels and reduced peroxisomal VLCFA beta-oxidation in human and mouse X-ALD fibroblasts. In this study, we found normal levels of peroxisomal VLCFA beta-oxidation in tissues from ALD mice with elevated VLCFA levels. Treatment of ALD mice with pharmacological agents resulted in decreased VLCFA levels without a change in VLCFA beta-oxidation activity. These data indicate that ALDP does not determine the rate of VLCFA beta-oxidation and that VLCFA levels are not determined by the rate of VLCFA beta-oxidation. The rate of peroxisomal VLCFA beta-oxidation in human and mouse fibroblasts in vitro is affected by the rate of mitochondrial long-chain fatty acid beta-oxidation. We hypothesize that ALDP facilitates the interaction between peroxisomes and mitochondria, resulting, when ALDP is deficient in X-ALD, in increased VLCFA accumulation despite normal peroxisomal VLCFA beta-oxidation in ALD mouse tissues. In support of this hypothesis, mitochondrial structural abnormalities were observed in adrenal cortical cells of ALD mice.     

Microglial Phagocytosis of Dopamine Neurons at Early Phases of Apoptosis

Transection of the medial forebrain bundle caused apoptosis of dopamine neurons in the rat substantia nigra. Immunohistochemical localization of activated microglia and tyrosine hydroxylase in the axotomized substantia nigra showed that activation of microglia was rapid and OX-6 (MHC-II marker)-positive and ED1 (lysosomal phagocytic marker)-positive microglia were apposed to structurally intact tyrosine hydroxylase-positive dopamine neurons, indicating microglial phagocytosis of degenerating dopamine neurons. The occurrence of microglial phagocytosis at early stages of apoptosis may indicate the evolution of apoptosis into an irreversible state. Alternatively, interventions that suppress early activation of microglia might lead to novel mechanisms for neuron protection.     

Modeling and docking of the three-dimensional structure of the human melanocortin 4 receptor

A three-dimensional structure of the human melanocortin 4 receptor (hMC4R) is constructed in this study using a computer-aided molecular modeling approach. Human melanocortin 4 receptor is a G Protein-Coupled Receptor (GPCR). We structurally aligned transmembrane helices with bovine rhodopsin transmembrane domains, simulated both intracellular and extracellular loop domains on homologous loop regions in other proteins of known 3D structure and modeled the C terminus on the corresponding part of bovine rhodopsin. Then tandem minimization and dynamics calculations were run to refine the crude structure. The simulative model was tested by docking with a triplet peptide (RFF) ligand. It was found that the ligand is located among transmembrane regions TM3, TM4, TM5, and TM6 of hMC4R. In consistence with mutational and biochemical data, binding site is mainly formed as a hydrophobic and negatively charged pocket. The model constructed here might provide a structural framework for making rational predictions in relevant fields.     

Effect of dietary pectin on the production of immunoglobulins and cytokines by mesenteric lymph node lymphocytes in mouse colitis induced with dextran sulfate sodium

The present study explores the dietary effect of pectin on the MLN lymphocyte functions of mice with dextran sulfate sodium (DS)-induced colitis. We found that the immunoglobulin (Ig)A level in mesenteric lymph node (MLN) lymphocytes was high, while the IgE level was lower, in mice fed with pectin than in those fed with cellulose. Interestingly, the fecal IgA concentration of the pectin-fed mice was significantly higher than that of the cellulose-fed mice. The concentrations of interferon-gamma and interleukin (IL)-2 treated with concanavalin A (ConA) were significantly higher in the pectin-fed group than in the cellulose-fed group. Although dietary pectin did not affect the IL-4 and IL-10 levels, the activation-induced IL-4 and IL-10 secretion was lower in MLN cells of the pectin-fed mice than of the cellulose-fed mice following DS-induced colitis. Based on these findings, we propose that the effect of dietary pectin on mice with DS-induced colitis is mediated by the manipulation of Th1 cells. Furthermore, the inhibitory effect of IL-4 and IL-10 by dietary pectin may play an important role in promoting a change in Th1/Th2 balance toward Th1-dominant immunity.     

Effects of degree of hydrolysis and pH on the solubility of heme-iron enriched peptide in hemoglobin hydrolysate

Hemoglobin was hydrolyzed with Esperase and Flavourzyme as the endopeptidase and exopeptidase, respectively. The solubility of the heme-iron enriched peptide fraction decreased as the degree of hydrolysis of the hydrolysate increased. When the pH of a hydrolysate was adjusted to 5.0 after simultaneous hydrolysis with the two enzymes, the solubility of heme-iron enriched peptide was nearly zero, and 98% of the heme-iron enriched peptide fraction was recovered as a precipitate. These results indicated that an effective separation method for the production of heme-iron enriched peptide could be established by pH adjustment of the hemoglobin hydrolysate with high degree of hydrolysis.     

The effect of manipulating ecdysteroid signaling on embryonic eye development in the locust<Emphasis Type="Italic"> Schistocerca americana</Emphasis>

Adult body plan differentiation in holometabolous insects depends on global induction and control by ecdysteroid hormones during the final phase of postembryogenesis. Studies in Drosophila melanogaster and Manduca sexta have shown that this pertains also to the development of the compound eye retina. It is unclear whether the hormonal control of postembryonic eye development in holometabolous insects represents evolutionary novelty or heritage from hemimetabolous insects, which develop compound eyes during embryogenesis. We therefore investigated the effect of manipulating ecdysteroid signaling in cultured embryonic eye primordia of the American desert locust Schistocerca americana, in which ecdysteroid level changes are known to induce three rounds of embryonic molt. Although at a considerably reduced rate compared to in vivo development, early differentiation and terminal maturation of the embryonic retina was observed in culture even if challenged with the ecdysteroid antagonist cucurbitacin B. Supplementing cultures with 20-hydroxyecdysone (20E) accelerated differentiation and maturation, and enhanced cell proliferation. Considering these results, and the relation between retina differentiation and ecdysteroid level changes during locust embryogenesis, we conclude that ecdysteroids are not an essential but possibly a modulatory component of embryonic retina development in S. americana. We furthermore found evidence that 20E initiated precocious epithelial morphogenesis of the posterior retinal margin indicating a more general role of ecdysteroids in insect embryogenesis.Electronic Supplementary Material Supplementary material is available in the online version of this article at Edited by C. Desplan     

Sol-gel-derived titanium oxide/copolymer composite based glucose biosensor

A new type of sol-gel-derived titanium oxide/copolymer composite material was developed and used for the construction of glucose biosensor. The composite material merged the best properties of the inorganic species, titanium oxide and the organic copolymer, poly(vinyl alcohol) grafting 4-vinylpyridine (PVA-g-PVP). The glucose oxidase entrapped in the composite matrix retained its bioactivity. Morphologies of the composite-modified electrode and the enzyme electrode were characterized with a scanning electron microscope. The dependence of the current responses on enzyme-loading and pH was studied. The response time of the biosensor was < 20 s and the linear range was up to 9 microM with a sensitivity of 405 nA/microM. The biosensor was stable for at least 1 month. In addition, the tetrathiafulvalene-mediated enzyme electrode was constructed for the decrease of detection potential and the effect of three common physiological sources that might interfere was also investigated.