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PubMed1995

Cavity depth and width effects on cyclophane-steroid recognition: molecular complexation of cholesterol and progesterone in aqueous solution.

BACKGROUND: Recent X-ray crystal structures show that steroid-binding proteins contain deep hydrophobic cavities defined by aromatic amino-acid side chains which encapsulate steroid molecules. These cavities resemble the binding site of a synthetic macrotricyclic cyclophane receptor which we recently reported to form complexes with cholesterol in aqueous solution. The binding affinity of the cyclophane-cholesterol complex (Ka approximately 10(6) M-1, 295 K) is similar to that measured for the cholesterol complex of steroid-transport proteins such as sterol carrier protein-2 (SCP-2). Here we describe synthesis and binding studies of a related receptor with a cavity that is wider and 2 A deeper than that of the previous cyclophane, and a comparison of the steroid-binding affinity and selectivity of the two synthetic receptors. RESULTS: A new tricyclic cyclophane receptor with a 13 A deep cavity was synthesized to study the effect of increased cavity depth on receptor selectivity for steroids. NMR analysis demonstrated that this receptor provided increased steroidal side-chain encapsulation with a corresponding gain in binding free energy of 0.9 kcal mol-1 (in d4-methanol) as compared to our previously reported 11 A deep receptor. An unexpected consequence of the increase in cavity depth was a corresponding enlargement of the cavity width, as indicated both by steroid-binding studies and molecular modeling. This enlargement in cavity width increases binding affinity for saturated steroids while decreasing the association strength of unsaturated steroids such as cholesterol. In water, cholesterol binds to the new receptor with Ka approximately 1.5 x 10(5) M-1 and exhibits a significant complexation-mediated solubility increase. CONCLUSIONS: Small changes in steroid receptor dimensions have resulted in large differences in steroid selectivity and binding affinity. These results indicate that potentially large gains in steroid-binding free energy may be obtainable from complete hydrophobic encapsulation of the flexible aliphatic steroidal side chain. These results have implications for the design of synthetic receptor mimics of natural steroid binding proteins.

Cholesterol↗

PubMed2006

Differential functions of tissue factor in the trans-activation of cellular signalling pathways.

In this study we examined the ability of tissue factor (TF) alone, or in conjunction with factor VIIa, factor Xa and TFPI in activating a number of key signalling pathways associated with cellular growth, stress and differentiation responses in human endothelial cells. We used luciferase reporter systems to demonstrate the activation of p42/44 MAPK by the TF-FVIIa complex, mediated via the PAR1 receptor. TF alone was capable of interacting with the cell surface and was sufficient to activate the JNK-SAPK pathway and subsequently AP-1, but the level of activation was enhanced by the activity of FXa on PAR1 and 2. Furthermore, the phosphorylated form of the transmembrane-cytoplasmic domain of TF was directly responsible for activation of these pathways. CREB activation occurred in response to TF-FVIIa in a non-protease dependent manner but was lowered on addition of FXa. Finally, NFkappaB activation occurred in response to FVIIa or FXa, with the latter exhibiting higher levels of activation. In conclusion, we have shown that TF is capable of activating differing signalling pathways, via more than one mechanism. The differential influence of TF is modified depending on the presence of other coagulation factors and ultimately acts as a deciding factor in the determination of cellular fate.

Cells, Cultured↗

PubMed2005

Accelerated atherosclerosis, immune response and autoimmune rheumatic diseases.

Atherosclerosis (AT) is a chronic autoimmune inflammatory disease, characterized by lipoproteins metabolism alteration leading to formation of pro-inflammatory and pro-oxidative lipids and immune response. Identification of macrophages, T cells, pro-inflammatory cytokines, adhesion cell molecules in atherosclerotic lesions support the hypothesis that innate and adaptive immune response participate in the atherogenesis mechanism. Multiple factors such as inflammatory, infectious and immune system, among others participate in this process. The principal antigens identified in atherogenesis are: oxidized LDL (oxLDL), HSPs and beta2GPI. During LDL oxidation, multiple neoantigens are formed (anti-EO). These antibodies seem to be protective. Systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) have accelerated AT. The association of both diseases with AT suggests a common pathogenic mechanism. SLE and atherosclerosis are immune-complex mediated diseases. Participation of complement activation, and CD40, CD40 ligand interactions have been demonstrated in AT and SLE. AT may be the initial presentation or the consequence of primary antiphospholipid syndrome. The similarities between AT, SLE, and APS and the identification of protective antibodies offer opportunities for new immunomodulation treatment strategies.

Arteriosclerosis↗

PubMed2006

Insulin resistance, chronic inflammatory state and the link with systemic lupus erythematosus-related coronary disease.

The association of SLE with atherosclerosis suggests a common pathogenic mechanism. SLE and atherosclerosis are immune complex-mediated diseases. The integration of metabolism and immunity, which under normal conditions is beneficial for the maintenance of good health, can become deteriorative under conditions of metabolic challenge, as exemplified by the immunosuppression characteristic of malnourished or starving individuals. It is now apparent that obesity is associated with a state of chronic inflammation, particularly in white adipose tissue. However, in the absence of obesity, infusion of animals with inflammatory cytokines or lipids can cause insulin resistance. It is possible that the stresses of obesity are similar enough to the stresses of an infection and the body reacts to obesity as it would to an infection. Atherosclerosis can be considered to have a significant chronic inflammatory component. Inflammation also contributes to the typical dyslipidemia associated with SLE that is characterized by elevations of VLDL, LDL and triglycerides as well as reduced HDL. The link between insulin resistance and SLE can be explained by the chronic inflammatory state, and the consequent dyslipoproteinemia.

Chronic Disease↗

PubMed2006

Behavioral effects of opioid subtypes compared with benzodiazepines in the staircase paradigm.

Opioid abuse is frequently associated with the abuse of benzodiazepines (BZ). Despite the fact that benzodiazepines and opioids act at totally separate receptor sites and through different biochemical and pharmacological mechanisms, they obviously interact with each other at some level. The present study was designed to investigate the behavioral effects of agents with activity on the opioid system and with the benzodiazepine receptor complex in the staircase paradigm. The benzodiazepine agonist lorazepam was used as a reference drug and showed a benzodiazepine effect: it reduced the rearing activity in mice in a dose-dependent manner, at doses that did not suppress climbing. Dissociation between the rearing and climbing behavior was not obtained with the administration of the opioid benzodiazepine, tifluadome, although tifluadome was antagonized by the BZ antagonist, flumazenil and not by naloxone, an opioid antagonist. An administration of opioids that act on the different subtype receptors morphine, U50 and SNC80, induced a dose dependent decrease in both the rearing and climbing activity, meaning no behavioral dissociation. Naloxone was found to have an antagonistic effect on morphine and U50-488H (micro and kappa subtype receptors, respectively), but no antagonistic effect on the delta subtype receptor agonist, SNC80. The administration of nalorphine to mice had no effect on both the rearing and climbing, in the staircase paradigm. When combining naloxone with the mentioned nalorphine, results showed the same effect, which was achieved with all the other opiates. This data, once again, supports the validity of the mouse staircase test for the identification of anxiolytic agents with a GABA(A) receptor complex-mediated activity, and for the ability to differentiate between diverse effects of the different opioids.

Animals↗

PubMed2004

Structural studies of oligonucleotides containing G-quadruplex motifs using AFM.

G-quadruplex DNAs are cyclic arrays of four guanine bases binding by Hoogsteen hydrogen bonds, found in the telomeric regions of chromosomes and in transcriptional regulatory regions of several important oncogenes. Here, we used high resolution atomic force microscopy (AFM) to observe a specific guanine (G) tetrad mediated complex formation of oligonucleotides containing a G-quadruplex motifs (G-ODN) combined with a palindromic sequence under physiological extracellular conditions. These oligonucleotides have been investigated in correlation to their immunostimulatory effects. We observed structural dependence on ion concentration and G-ODN concentration, where high concentration self-assembled DNA networks were formed.

Adjuvants, Immunologic↗

PubMed2004

Regulation of large-scale chromatin unfolding by Smad4.

The tumor suppressor Smad4 plays a critical role in the transforming growth factor-beta (TGF-beta signaling pathway. Smad4 is an essential component of transcriptional complexes mediating the activation of Smad-dependent target genes. However, how Smad4 regulates various chromosomal events remains unknown. Here, we report that Smad4 induces large-scale chromatin unfolding by targeting Smad4 to an amplified, lac operator-containing chromosome region in mammalian cells. This unfolding activity maps to the subdomains within the transactivation domain of Smad4. Both the N-terminal missense and the C-terminal truncated tumor-derived mutations increased the chromatin unfolding activity of Smad4. These data identify a novel function of Smad4 and suggest that regulation of large-scale chromatin unfolding by Smad4 may be responsible for cancer development.

Alleles↗

PubMed2005

Identification of an evolutionary conserved SURF-6 domain in a family of nucleolar proteins extending from human to yeast.

The mammalian SURF-6 protein is localized in the nucleolus, yet its function remains elusive in the recently characterized nucleolar proteome. We discovered by searching the Protein families database that a unique evolutionary conserved SURF-6 domain is present in the carboxy-terminal of a novel family of eukaryotic proteins extending from human to yeast. By using the enhanced green fluorescent protein as a fusion protein marker in mammalian cells, we show that proteins from distantly related taxonomic groups containing the SURF-6 domain are localized in the nucleolus. Deletion sequence analysis shows that multiple regions of the SURF-6 protein are capable of nucleolar targeting independently of the evolutionary conserved domain. We identified that the Saccharomyces cerevisiae member of the SURF-6 family, named rrp14 or ykl082c, has been categorized in yeast databases to interact with proteins involved in ribosomal biogenesis and cell polarity. These results classify SURF-6 as a new family of nucleolar proteins in the eukaryotic kingdom and point out that SURF-6 has a distinct domain within the known nucleolar proteome that may mediate complex protein-protein interactions for analogous processes between yeast and mammalian cells.

Amino Acid Sequence↗

PubMed2005

Remote NADH imaging through an ordered array of electrochemiluminescent nanoapertures.

In this report, we present an ordered array comprising thousands of nanoapertures for the electrochemiluminescent (ECL) detection of NADH. It was fabricated on the distal face of a coherent optical fiber bundle. Such a high-density array of nanoapertures combines optical, imaging and electrochemical properties. Indeed, each nanoaperture is surrounded by a gold nanoring, which acts as an electrode material. The behavior of the array was characterized by cyclic voltammetry and it shows excellent electrochemical performances. NADH is the analyte, which is measured in presence of Ru(bpy)3(2+). The ruthenium complex mediates the NADH oxidation and this coenzyme acts as a co-reactant in the ECL mechanism. ECL light is generated at the distal face of the array by each gold ring electrode. A fraction of this ECL light is collected by the corresponding nanoaperture, transmitted through the optical fiber bundle and finally imaged on the proximal face with a CCD camera. In this work, we show that NADH concentration is remotely detected by an oxidative-reductive ECL mechanism. We present also some preliminary results about the ECL process of NADH with Ru(bpy)3(2+). The ECL behavior of NADH on gold surface is reported. The influence of the applied potential on the collected light intensity was investigated. The variation of the ECL intensity measured through the nanoaperture array with NADH concentration is linear. Remote ECL detection of NADH is spatially resolved over a large area with a micrometer resolution through the array. Therefore, such array integrates several complementary functions: ECL light generation, collection, transmission and remote imaging in an array format.

Electrochemistry↗

PubMed2004

Wiring of PQQ-dehydrogenases.

The performance of pyrroloquinoline quinone (PQQ) dependent alcohol dehydrogenase (ADH) and two types of PQQ-glucose dehydrogenases in solution and when immobilized on the carbon paste electrodes modified with ferrocene derivatives is investigated. The immobilization of ADH consisting of PQQ and four hemes improves its stability up to 10 times. Both PQQ and heme moieties are involved in the electron transport from substrate to electrode. The ferrocene derivatives improve the electron transport 10-fold. Membrane-bound alcohol dehydrogenase from Gluconobacter sp. 33, intracellular soluble glucose dehydrogenase from Acinetobacter calcoaceticus L.M.D. 79.41 (s-GDH), and the membrane-bound enzyme (m-GDH) from Erwinia sp. 34-1 were purified and investigated. Soluble and membrane-bound PQQ-glucose dehydrogenases display different behavior during the immobilization on the modified carbon electrodes. The immobilization of s-GDH leads to a decrease in both stability and substrate specificity of the enzyme. This suggests that PQQ dissociates from the enzyme active center and operates as a free-diffusing mediator. The rate-limiting step of the process is likely the loading of PQQ onto the apo-enzyme. The immobilization of m-GDH leads to its substantial stabilization and improves the substrate specificity. The nature of m-GDH binding to the electrode surface is presumably similar to the binding to the cell membrane through its anchor-subunit. The enzyme operates as an enzyme and mediator complex.

Adsorption↗

PubMed2005

Quantitative models of nuclear transport.

Nuclear pore complexes mediate the rapid trafficking of target macromolecules between the nucleus and the cytoplasm but exclude non-targets. Mathematical modeling helps to define the physical properties of a transport medium that can selectively enhance the permeation of some molecules but block others. Recent pioneering work has established a basis for quantitative modeling of nuclear translocation, and we expect this field to expand rapidly. A second area where modeling of nucleocytoplasmic transport has been prominently employed is in efforts to understand the regulatory networks by which signals pass between the nuclear and cytoplasmic compartments. Recent evidence suggests that the distinctive kinetics and spatial organization of nuclear transport processes can be used to efficiently propagate signals by new and unexpected pathways.

Active Transport, Cell Nucleus↗

PubMed2005

How the T cell receptor sees antigen--a structural view.

Structures of many of the cell surface receptor-ligand complexes mediating the interactions between T cells and target cells have been determined in the past ten years. While snapshots of T cell receptors bound to their peptide-MHC ligands appear to have defined a general interaction or "docking" solution, many of the most fundamental structural questions in antigen recognition lack detailed answers and thus pose exciting experimental challenges for the future.

Animals↗

PubMed2006

Prolongation of alloskin graft survival by catalytic scavengers of reactive oxygen species.

We tested the effects of salen manganese (Salen-Mn) complexes, which are scavengers of reactive oxygen species exhibiting superoxide dismutase and catalase activities on the rejection of and alloresponse to fully allogeneic skin grafts in mice. We showed that pre-transplant treatment of C57Bl/6 donor skin or of BALB/c recipients with Salen-Mn complexes significantly delayed allograft rejection. ELISPOT analysis of alloimmune response of treated mice revealed a significant reduction of the frequency of type 1 cytokine (pro-inflammatory) producing T-cells, while the number of activated T-cells producing type 2 cytokines was elevated. In addition, anti-oxidative treatment of graft recipients resulted in a profound inhibition of their donor-specific cytotoxic T-cell response. Our results indicate that salen manganese complexes mediate their effect on graft rejection both by reducing the susceptibility of graft tissue to ROS-mediated injury and by exerting an anti-inflammatory effect in recipients.

Animals↗

PubMed2005

Immunology of alcoholic liver disease.

Alcohol-induced liver injury is a reflection of the immunologic response of the liver to this stimulus. Reported studies of immunologic abnormalities in alcoholic liver disease (ALD) patients suggest that immunologic response plays a key role in the pathogenesis of chronic liver disease in alcoholics, and have contributed to the understanding of how some patients with ALD progress into alcoholic liver cirrhosis. The immunologic response of the liver is reflected in alcoholic fatty liver disease, hyaline necrosis, and cirrhosis, promoted by the role of neutrophils in damaging liver cells through cytotoxicity, and lymphocytes through cytotoxicity, inducing fibrogenesis of the liver and formation of immune complexes responsible for immune complex-mediated cytotoxicity, in addition to the role of different chemokines in attracting leucocytes, inducing fibrogenesis and liver cell apoptosis, with the established mechanism by which Mallory bodies evoke both cellular and humoral immunity contributing to the process of alcoholic liver cirrhosis, which plays a key role in transformation of alcoholic hepatitis to cirrhosis. At present, research is underway to find modalities to correct the induced immunologic changes, so at this time, it is necessary to avoid alcoholism, with the use of social and educational programs to stop alcoholism.

Chemokines↗

PubMed2006

Various domains of the B-cell regulatory molecule CD72 has diverged at different rates in mammals: cloning, transcription and mapping of porcine CD72.

We report the cloning of the porcine B-cell co-receptor CD72, as well as genomic mapping and examination of transcription. The B-cell receptor (BCR) complex mediates signalling upon antigen recognition by the membrane bound BCR. Several co-receptors modulate this signal positively or negatively. CD72 has been shown to be a negatively regulating BCR co-receptor. We isolated and sequenced three porcine CD72 transcript variants. Using a pig radiation hybrid panel we found the porcine CD72 gene to be located on chromosome 1q21-28 in a region syntenic to human chromosome 9. The porcine CD72 gene is highly transcribed in lymph node, thymus and lung tissues as well as in pulmonary alveolar macrophages. The predicted porcine CD72 polypeptide shows conservation of immunoreceptor tyrosine-based inhibitory motifs and an extracellular C-type lectin domain. Compared to CD72 sequences from other mammals as well as from chicken, the polypeptide is highly conserved in the intracellular part and much less conserved in the extracellular part. We suggest that this difference might be due to the different nature of ligands and the constrains on these to co-evolve.

Alternative Splicing↗

PubMed2005

IgA1 is the premier serum glycoprotein recognized by human galectin-1 since T antigen (Galbeta1-->3GalNAc-) is far superior to non-repeating N-acetyl lactosamine as ligand.

Human heart galectin-1 (HHL) was separated by high pressure liquid chromatography from endogenous glycoproteins co-purified with it during affinity chromatography. These glycoproteins offered excellent ligands for HHL binding and were rich in T antigen (Galbeta1-->3 GalNAc-) of O-linked oligosaccharides. In enzyme linked lectin assay and hemagglutination inhibition assay, human IgA1, bovine fetuin and other O-glycosylated T antigen-bearing glycoproteins bound to the lectin efficiently in contrast to single N-acetyl lactosamine (LacNAc)-bearing N-linked oligosaccharides released from them and to IgG which is not O-glycosylated. HHL binding to IgA1 and fetuin was unaffected by removal of their N-linked oligosaccharides by alpha-mannosidase. When immobilized, O-glycosylated serum proteins but not IgG could capture HHL from its solutions. Desialylated or polymeric IgA1 was better inhibitor than monomeric IgA1. The findings suggest a possible role for galectin-1 in anchoring of microbial and cancer cells known to be rich in T antigen, in high serum IgA1 turn over and in tissue sequestering of IgA1 immune complexes especially after their microbial desialylation in IgA nephropathy and other immune complex-mediated disorders.

Acetylgalactosamine↗

PubMed2005

Identification of FcalphaRI as an inhibitory receptor that controls inflammation: dual role of FcRgamma ITAM.

Serum IgA is considered a discrete housekeeper of the immune system with multiple anti-inflammatory functions, whereas IgA-immune complexes mediate inflammatory responses. Here, we identify FcalphaRI as a molecular device that determines the nature of IgA responses. In the absence of sustained aggregation, receptor targeting by serum IgA or anti-FcalphaRI Fab inhibits activating responses of heterologous FcgammaR or FcepsilonRI. The inhibitory mechanism involves recruitment of tyrosine phosphatase SHP-1 to FcalphaRI and impairment of Syk, LAT, and ERK phosphorylation induced by FcepsilonRI engagement. SHP-1 recruitment is dependent on ERK. Conversely, sustained aggregation of FcalphaRI by multimeric ligands stimulates cell activation by recruiting high amounts of Syk and aborting SHP-1 binding. Both types of signals require the FcRgamma-ITAM motif. Anti-FcalphaRI Fab treatment suppresses manifestations of allergic asthma in FcalphaRI transgenic mice. These findings redefine FcalphaRI as a bifunctional inhibitory/activating receptor of the immune system that mediates both anti- and proinflammatory functions of IgA.

Animals↗

PubMed2006

Characterization by theory of H-transfers and onium reactions of CH3CH2CH2N+H=CH2.

H-transfers by 4-, 5-, and 6-membered ring transition states to the pi-bonded methylene of CH3CH2CH2NH+=CH2 (1) are characterized by theory and compared with the corresponding transfers in cation radicals. Four-membered ring H-transfers converting 1 to CH3CH2CH=N+HCH3 (2) and CH3N+H=CH2 to CH2=NH+CH3 are high-energy processes involving rotation of the source and destination RHC= groups (R = H or C2H5) to near bisection by skeletal planes; migrating hydrogens move near these planes. The H-transfer 1 --> CH3C+HCH2NHCH3 (3) has a higher energy transition-state than 1 --> 2, in marked contrast to the corresponding relative energies of 4- and 5-membered ring H-transfers in cation-radicals. Six-membered ring H-transfer-dissociation (1 --> CH2=CH2 + CH2=N+HCH3) is a closed shell analog of the McLafferty rearrangement. It has a lower energy transition-state than either 1 --> 2 or 1 --> 3, but is still a much higher energy process than 6-membered ring H-transfers in aliphatic cation radicals. In contrast to the stepwise McLafferty rearrangement in cation radicals, H-transfer and CC bond breaking are highly synchronous in 1 --> CH3N+H=CH2 + CH2=CH2. H-transfers in propene elimination from 1 are ion-neutral complex-mediated: 1--> [CH3CH2CH2+ ---NH=CH2] --> [CH3C+HCH3 NH=CH2] --> CH3CH = CH2 + CH2=NH2+. Intrinsic reaction coordinate tracing demonstrated that a slight preference for H-transfer from the methyl containing the carbon from which CH2=NH is cleaved is due to CH2=NH passing nearer this methyl than the other on its way to abstracting H, i.e., some memory of the initial orientation of the partners accompanies this reaction.

Energy Transfer↗