Regulation of the alpha-fetoprotein promoter: Ku binding and DNA spatial conformation

This work shows that the proximal promoter of the mouse Afp gene contains a Ku binding site and that Ku binding is associated with down-regulation of the transcriptional activity of the Afp promoter. The Ku binding site is located in a segment able to adopt a peculiar structured form, probably a hairpin structure. Interestingly, the structured form eliminates the binding sites of the positive transcription factor HNF1. Furthermore, a DNAse hypersensitive site is detected in footprinting experiments done with extracts of AFP non-expressing hepatoma cells. These observations suggest that the structured form is stabilised by Ku and is associated with extinction of the gene in AFP non-expressing hepatic cells.

Central nervous system drugs: Low temperature X-ray structures of (I) the base 5-(2,3-dichlorophenyl)-2,4-diamino-6-fluoromethyl-pyrimidine (4030W92) and (II) 5-(2,6-dichlorophenyl)-1-H-2,4-diamino-6-methyl-pyrimidine methanesulphonic acid salt (227C89)

The X-ray crystal structures of (I), the base 4030W92, 5-(2,3-dichlorophenyl)-2,4-diamino-6-fluoromethyl-pyrimidine, C11H9Cl2FN4, and (II) 227C89, the methanesulphonic acid salt of 5-(2,6-dichlorophenyl)-1-H-2,4-diamino-6-methyl-pyrimidine, C11H11Cl2N4 center dot CH3O3S, have been carried out at low temperature. A detailed comparison of the two structures is given. Structure (I) is non-centrosymmetric, crystallizing in space group P2(1) with unit cell a = 10.821(3), b = 8.290(3), c = 13.819(4) angstrom, beta = 105.980(6)degrees, V = 1191.8(6) angstrom(3), Z = 4 (two molecules per asymmetric unit) and density (calculated) = 1.600 mg/m(3). Structure (II) crystallizes in the triclinic space group P (1) over bar with unit cell a = 7.686(2), b = 8.233(2), c = 12.234(2) angstrom, alpha = 78.379(4), beta = 87.195(4), gamma = 86.811(4)degrees, V = 756.6(2) angstrom(3), Z = 2, density (calculated) = 1.603 mg/m(3). Final R indices [I > 2sigma(I)] are R1 = 0.0572, wR2 = 0.1003 for (I) and R1 = 0.0558, wR2 = 0.0982 for (II). R indices (all data) are R1 = 0.0983, wR2 = 0.1116 for (I) and R1 = 0.1009, wR2 = 0.1117 for (II). 5- Phenyl-2,4 diaminopyrimidine and 6-phenyl-1,2,4 triazine derivatives, which include lamotrigine (3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine), have been investigated for some time for their effects on the central nervous system. The three dimensional structures reported here form part of a newly developed data base for the detailed investigation of members of this structural series and their biological activities.

Effect of caffeine ingestion during prolonged exhaustive exercise on salivary immunoglobulin A, alpha-amylase and cortisol

Exercise can have deleterious effects on the secretion of salivary immunoglobulin A (s-IgA), which appears to be related to perturbations in sympatheticoadrenal activation (Teeuw et al., 2004). Caffeine, commonly used for its ergogenic properties is associated with increased sympathetic nervous system activity, and it has been previously shown that caffeine ingestion before intensive cycling enhances s-IgA responses during exercise (Bishop et al., 2006). Therefore, the aim of the present study was to examine the effect of a performance cereal bar, containing caffeine, before and during prolonged exhaustive cycling on exercise performance and the salivary secretion of IgA, alpha-amylase activity and cortisol. Using a randomised cross-over design and following a 10 – 12 hour overnight fast, 12 trained cyclists, mean (SEM) age: 21(1) yr; height: 179(2) cm; body mass: 73.6(2.5) kg; maximal oxygen uptake, VO2max: 57.9(1.2) completed 2.5 h of cycling at 60%VO2max (with regular water ingestion) on a stationary ergometer, which was followed by a ride to exhaustion at 75% VO2max. Immediately before exercise, and after 55 min and 115 min of exercise participants ingested a 0.9 MJ cereal bar containing 45 g carbohydrate, 5 g protein, 3 g fat and 100 mg of caffeine (CAF) or an isocaloric noncaffeine bar (PLA). Unstimulated timed saliva samples were collected immediately before exercise, after 70 min and 130 min of exercise, and immediately after the exhaustive exercise bout. Saliva was analysed for s-IgA, alpha-amylase activity and cortisol concentration. Saliva flow rates were determined to calculate the s-IgA secretion rate. Data were analysed using a 2-way repeated measures ANOVA and post-hoc t-tests with Holm Bonferroni adjustments applied where appropriate. Time to exhaustion was 35% longer in CAF compared with PLA ((2177 (0.2) vs 1615 (0.16) s; P < 0.05)). Saliva flow rate did not change significantly during the exercise protocol. Exercise was associated with elevations in s-IgA concentration (9% increase), s-IgA secretion rate (24% increase) and alpha-amylase activity (224% increase) post-exhaustion (P < 0.01), but there was no effect of CAF on these responses. Salivary cortisol concentration increased by 64% post-exhaustion in the CAF trial only (P < 0.05), indicating an increase in adrenal activity following caffeine ingestion. Values were 35.7 (5.5) and 19.6 (3.4) nmol/L post-exhaustion for CAF and PLA, respectively. These findings show that ingestion of a caffeine containing cereal bar during prolonged exhaustive cycling enhances endurance performance, increases salivary cortisol secretion post-exhaustion, but does not affect the exercise-induced increases in s-IgA or alpha-amylase activity.

Structure and denaturation of 4-chlorobenzoyl coenzyme A dehalogenase from Arthrobacter sp. strain TM-1

The secondary structure of the trimeric protein 4-chlorobenzoyl coenzyme A dehalogenase from Arthrobacter sp. strain TM-1, the second of three enzymes involved in the dechlorination of 4-chlorobenzoate to form 4-hydroxybenzoate, has been examined. E(mM) for the enzyme was 12.59. Analysis by circular dichroism spectrometry in the far uv indicated that 4-chlorobenzoyl coenzyme A dehalogenase was composed mostly of alpha-helix (56%) with lesser amounts of random coil (21%), beta-turn (13%) and beta-sheet (9%). These data are in close agreement with a computational prediction of secondary structure from the primary amino acid sequence, which indicated 55.8% alpha-helix, 33.7% random coil and 10.5% beta-sheet; the enzyme is, therefore, similar to the 4-chlorobenzoyl coenzyme A dehalogenase from Pseudomonas sp. CBS-3. The three-dimensional structure, including that of the presumed active site, predicted by computational analysis, is also closely similar to that of the Pseudomonas dehalogenase. Study of the stability and physicochemical properties revealed that at room temperature, the enzyme was stable for 24 h but was completely inactivated by heating to 60 degrees C for 5 min; thereafter by cooling at 1 degrees C min(-1) to 45 degrees C, 20.6% of the activity could be recovered. Mildly acidic (pH 5.2) or alkaline (pH 10.1) conditions caused complete inactivation, but activity was fully recovered on returning the enzyme to pH 7.4. Circular dichroism studies also indicated that secondary structure was little altered by heating to 60 degrees C, or by changing the pH from 7.4 to 6.0 or 9.2. Complete, irreversible destruction of, and maximal decrease in the fluorescence yield of the protein at 330-350 nm were brought about by 4.5 M urea or 1.1 M guanidinium chloride. Evidence was obtained to support the hypothetical three-dimensional model, that residues W140 and W167 are buried in a non-polar environment, whereas W182 appears at or close to the surface of the protein. At least one of the enzymes of the dehalogenase system (the combined 4-chlorobenzoate:CoA ligase, the dehalogenase and 4-hydroxybenzoyl coenzyme A thioesterase) appears to be capable of association with the cell membrane.

An alpha 2-macroglobulin-like protein is the cue to gregarious settlement of the barnacle Balanus amphitrite

Many benthic marine invertebrates, like barnacles, have a planktonic larval stage whose primary purpose is dispersal. How these species colonize suitable substrata is fundamental to understanding their evolution, population biology, and wider community dynamics. Unlike larval dispersal, settlement occurs on a relatively small spatial scale and involves larval behavior in response to physical and chemical characteristics of the substratum. Biogenic chemical cues have been implicated in this process. Their identification, however, has proven challenging, no more so than for the chemical basis of barnacle gregariousness, which was first described >50 years ago. We now report that a biological cue to gregarious settlement, the settlement-inducing protein complex (SIPC), of the major fouling barnacle Balanus amphitrite is a previously undescribed glycoprotein. The SIPC shares a 30% sequence homology with the thioester-containing family of proteins that includes the alpha sub(2)-macroglobulins. The cDNA (5.2 kb) of the SIPC encodes a protein precursor comprising 1,547 aa with a 17-residue signal peptide region. A number of structural characteristics and the absence of a thioester bond in the SIPC suggest that this molecule is a previously undescribed protein that may have evolved by duplication from an ancestral alpha sub(2)-macroglobulin gene. Although the SIPC is regarded as an adult cue that is recognized by the cyprid at settlement, it is also expressed in the juvenile and in larvae, where it may function in larva-larva settlement interactions.

A Possible Role Of Alpha-Amylase Isoenzymes From The Style Of The Mussel Choromytilus-Meridionalis (Krauss) Following Thermal-Acclimation

Separation of the proteins comprising the crystalline style of the mussel Choromytilus meridionalis (Krauss) by anion exchange chromatography shows that there are three fractions displaying α-amylase activity in both warm- and cold-acclimated mussels. These fractions correspond with one or more proteins which remain unbound to the resin (Peak I), a bound fraction which is eluted at 100–150 mM NaCl (Peak II) and a further fraction which is eluted at 200–250 mM NaCl (Peak III) but which may represent contamination carried over from Peak II. Cold-acclimation to 8°C results in the appearance of a fourth α-amylase fraction (Peak IV) which is eluted from the column between 300–400 mM NaCl. Thermal acclimation also results in changes in the activities of Fractions I–IV such that a specific activity of 0.47 mg glucose liberated per A280 unit of protein per 8 min incubation at 8°C in Fraction IV is increased nearly 10-fold to a specific rate of 4.10 in protein Fraction I following acclimation to 22°C. It is suggested that an increased of digestive activity may be of equal importance to a suppression of metabolic costs in the maintenance of energy flow into growth and reproduction in ectothermic organisms which experience an increase of environmental temperature, especially in bivalves such as C. meridionalis which do not show a compensatory increase in filtration rate.

Inhibition and fibril formation and toxicity of a fragment of alpha-synuclein by an N-methylated peptide analogue

Alpha-synuclein has been linked to amyloidogenesis in Parkinson's disease and other neurodegenerative disorders. We have previously shown that a peptide comprising residues 68-78 of alpha-synuclein is the minimum fragment that, like alpha-synuclein itself, forms amyloid fibrils and exhibits toxicity towards cells in culture. Hughes et al. [J. Biol. Chem. 275 (2000) 25109] showed that an N-methylated derivative of Abeta(25-35) inhibited the formation of fibrils by Abeta(25-35) and reduced its toxicity. We have now extended this concept to an amyloidogenic alpha-synuclein-based peptide. Alpha-synuclein(68-78), N-methylated at G1y73, was compared to non-methylated peptide. Whereas alpha-synuclein(68-78) formed fibrils and was toxic to cells, the N-methylated analogue had neither of these properties. Moreover, an equimolar mixture of the non-methylated and methylated peptides formed very few fibrils and toxicity was markedly reduced.

Aggregation and neurotoxicity of alpha-synuclein and related peptides

Fibrillar deposits of alpha-synuclein occur in several neurodegenerative diseases. Two mutant forms of alpha-synuclein have been associated with early-onset Parkinson's disease, and a fragment has been identified as the non-amyloid-beta peptide component of Alzheimer's disease amyloid (NAC). Upon aging, solutions of alpha-synuclein and NAC change conformation to beta-sheet, detectable by CD spectroscopy, and form oligomers that deposit as amyloid-like fibrils, detectable by electron microscopy. These aged peptides are also neurotoxic. Experiments on fragments of NAC have enabled the region of NAC responsible for its aggregation and toxicity to be identified. NAC(8-18) is the smallest fragment that aggregates, as indicated by the concentration of peptide remaining in solution after 3 days, and forms fibrils, as determined by electron microscopy. Fragments NAC(8-18) and NAC(8-16) are toxic, whereas NAC(12-18), NAC(9-16) and NAC(8-15) are not. Hence residues 8-16 of NAC comprise the region crucial for toxicity. Toxicity induced by alpha-synuclein, NAC and NAC(1-18) oligomers occurs via an apoptotic mechanism, possibly initiated by oxidative damage, since these peptides liberate hydroxyl radicals in the presence of iron. Molecules with anti-aggregational and/or antioxidant properties may therefore be potential therapeutic agents.

Enhanced inflammatory responses in alpha-tocopherol transfer protein null mice

The liver preferentially secretes alpha-tocopherol into plasma under the control of the hepatic alpha-tocopherol transfer protein (alpha-TTP). alpha-TTP-null mice (Ttpa(-/-) mice) are vitamin E deficient, therefore were used for investigations of in vivo responses to sub-normal tissue alpha-tocopherol concentrations during inflammation. Increased basal oxidative stress in Ttpa(-/-) mice was documented by increased plasma lipid peroxidation, and superoxide production by bone marrow-derived neutrophils stimulated in vitro with phorbol 12-myristate 13-acetate. Lipopolysaccharide (LPS) injected intraperitoneally induced increases in lung and liver HO-1 and iNOS, as well as plasma NO(x) in Ttpa(+/+) mice. LPS induced more modest increases in these markers in Ttpa(-/-) mice, while more marked increases in plasma IL-10 and lung lavage TNF alpha were observed. Taken together, these results demonstrate that alpha-tocopherol is important for proper modulation of inflammatory responses and that sub-optimal alpha-tocopherol concentrations may derange inflammatory-immune responses.

Preproendothelin-1 expression in human mesangial cells: evidence for a p38 mitogen-activated protein kinase/protein kinases- C-dependent mechanism

Endothelin-1 (ET-1) has been implicated in the pathogenesis of renal inflammation. This study investigated the mechanisms underlying the synergistic upregulation of preproET-1 gene expression in human mesangial cells after co-stimulation with thrombin and tumor necrosis factor alpha (TNFalpha). Whereas thrombin induced a moderate upregulation of preproET-1 mRNA, co-stimulation with TNFalpha resulted in a strong and protracted upregulation of this mRNA species. Thrombin+TNFalpha-induced upregulation of preproET-1 expression was found to require p38 mitogen-activated protein kinase and protein kinases C, whereas activation of extracellular signal-regulated kinase, c-Jun-N-terminal kinase, or intracellular Ca(2+) release were not required. Actinomycin D chase experiments suggested that enhanced stability of preproET-1 mRNA did not account for the increase in transcript levels. PreproET-1 promoter analysis demonstrated that the 5'-flanking region of preproET-1 encompassed positive regulatory elements engaged by thrombin. Negative modulation of thrombin-induced activation exerted by the distal 5' portion of preproET-1 promoter (-4.4 kbp to 204 bp) was overcome by co-stimulation with TNFalpha, providing a possible mechanism underlying the synergistic upregulation of preproET-1 expression by these two agonists. In conclusion, human mesangial cell expression of preproET-1 may be increased potently in the presence of two common proinflammatory mediators, thereby providing a potential mechanism for ET-1 production in inflammatory renal disease.

Recombinant alpha 2(IV)NC1 domain of type IV collagen is an effective regulator of retinal capillary endothelial cell proliferation and inhibits pre-retinal neovascularisation

Background A recombinant form of the alpha 2(IV)NC1 domain of type IV collagen has been shown to have potent anti-angiogenic activity although this peptide has not been studied in the context of proliferative retinopathies. In the current investigation we examined the potential for alpha 2(IV) NC1 to regulate retinal microvascular endothelial cell function using a range of in vitro and in vivo assay systems.

ICln, a novel integrin alpha(11b)beta3-associated protein, functionally regulates platelet activation.

A critical role for the conserved -integrin cytoplasmic motif, KVGFFKR, is recognized in the regulation of activation of the platelet integrin IIb3. To understand the molecular mechanisms of this regulation, we sought to determine the nature of the protein interactions with this cytoplasmic motif. We used a tagged synthetic peptide, biotin-KVGFFKR, to probe a high density protein expression array (37,200 recombinant human proteins) for high affinity interactions. A number of potential integrin-binding proteins were identified. One such protein, a chloride channel regulatory protein, ICln, was characterized further because its affinity for the integrin peptide was highest as was its expression in platelets. We verified the presence of ICln in human platelets by PCR, Western blots, immunohistochemistry, and its co-association with IIb3 by surface plasmon resonance. The affinity of this interaction was 82.2 ± 24.4 nM in a cell free assay. ICln co-immunoprecipitates with IIb3 in platelet lysates demonstrating that this interaction is physiologically relevant. Furthermore, immobilized KVGFFKR peptides, but not control KAAAAAR peptides, specifically extract ICln from platelet lysates. Acyclovir (100 µM to 5 mM), a pharmacological inhibitor of the ICln chloride channel, specifically inhibits integrin activation (PAC-1 expression) and platelet aggregation without affecting CD62 P expression confirming a specific role for ICln in integrin activation. In parallel, a cell-permeable peptide corresponding to the potential integrin-recognition domain on ICln (AKFEEE, 10–100 µM) also inhibits platelet function. Thus, we have identified, verified, and characterized a novel functional interaction between the platelet integrin and ICln, in the platelet membrane.

Truncated estrogen receptor alpha 46-kDa isoform in human endothelial cells: relationship to acute activation of nitric oxide synthase.

Background Estrogen acutely activates endothelial nitric oxide synthase (eNOS). However, the identity of the receptors involved in this rapid response remains unclear. Methods and Results We detected an estrogen receptor (ER) transcript in human endothelial cells that encodes a truncated 46-kDa ER (1a-hER-46). A corresponding 46-kDa ER protein was identified in endothelial cell lysates. Transfection of cDNAs encoding the full-length ER (ER-66) and 1a-hER-46 resulted in appropriately sized recombinant proteins identified by anti-ER antibodies. Confocal microscopy revealed that a proportion of both ER-66 and hER-46 was localized outside the nucleus and mediated specific cell-surface binding of estrogen as assessed by FITC-conjugated, BSA-estrogen binding studies. Both ER isoforms colocalized with eNOS and mediated acute activation of eNOS in response to estrogen stimulation. However, estrogen-stimulated transcriptional activation mediated by 1a-hER-46 was much less than with ER-66. Furthermore, 1a-hER-46 inhibited classical hER-66 mediated transcriptional activation in a dominant-negative fashion. Conclusions These findings suggest that expression of an alternatively spliced, truncated ER isoform in human endothelial cells confers a unique ability to mediate acute but not transcriptional responses to estrogen.