Suppression of experimental autoimmune encephalomyelitis using peptide mimics of CD28

The B7:CD28/CTLA-4 costimulatory pathway plays a critical role in regulating the immune response and thus provides an ideal target for therapeutic manipulation of autoimmune disease. Previous studies have shown that blockade of CD28 signaling by mAbs can both prevent and exacerbate experimental autoimmune encephalomyelitis (EAE). In this study, we have designed two CD28 peptide mimics that selectively block B7:CD28 interactions. By surface plasmon resonance, both the end group-blocked CD28 peptide (EL-CD28) and its retro-inverso isomer (RI-CD28) compete effectively with the extracellular domain of CD28 for binding to B7-1. Both the CD28 peptide mimics inhibited expansion of encephalitogenic T cells in vitro. A single administration of EL-CD28 or RI-CD28 peptide significantly reduced disease severity in EAE. Importantly, we show that either CD28 peptide mimic administered during acute disease dramatically improved clinical signs of EAE, suppressing ongoing disease. The ratio of CD80:CD86 expression was significantly lower on CD4(+) and F4/80(+) spleen cells in CD28 peptide-treated mice. Peripheral deletion of Ag-specific CD4(+) T cells occurs following in vivo blockade of CD28 with synthetic CD28 peptides.     

Induction of oxidative stress and histopathological changes by sub-chronic doses of triazophos

The effect of triazophos (O, O-diethyl O-1-phenyl-1 H-1, 2, 4-triazol-3-yl phosphorothioate), a widely used insecticide was studied on the induction of oxidative stress and histological alterations at sub-chronic doses in male albino rats. Oral administration of triazophos at concentrations of 1.64, 3.2 and 8.2 mg/kg body wt for 30 days produced dose as well as time-dependent increase in the lipid peroxidation (determined by malondialdehyde levels) and glutathione-S-transferase (GST) activity in serum with aconcomitant decrease in ferric reducing ability of plasma (FRAP) and blood glutathione (GSH) content. Histopathological examination of liver of triazophos-treated rats showed significant and progressive degenerative changes as compared to control, which could be due to induction of oxidative stress. However, no significant histopathological changes were observed in spleen, kidney and brain at either dose of triazophos with respect to control. These results indicated that oral administration of triazophos was associated with enhanced lipid peroxidation and compromised antioxidant defence in rats in dose and time-dependent manner. Thus the present study demonstrated for the first time the role of oxidative stress as the important mechanism involved in the stimulation of hepatic histoarchitectural alterations at sub-chronic doses of triazophos in rats.     

Role of intrinsic disorder in transient interactions of hub proteins

Hubs in the protein-protein interaction network have been classified as "party" hubs, which are highly correlated in their mRNA expression with their partners while "date" hubs show lesser correlation. In this study, we explored the role of intrinsic disorder in date and party hub interactions. The data reveals that intrinsic disorder is significantly enriched in date hub proteins when compared with party hub proteins. Intrinsic disorder has been largely implicated in transient binding interactions. The disorder to order transition, which occurs during binding interactions in disordered regions, renders the interaction highly reversible while maintaining the high specificity. The enrichment of intrinsic disorder in date hubs may facilitate transient interactions, which might be required for date hubs to interact with different partners at different times.     

Investigation of Cigarette Smoking among Male Schizophrenia Patients

Male schizophrenia patients are known to have a heavier smoking pattern compared with the general population. However, the mechanism for this association is not known, though hypothesis that smoking could alleviate symptomatology of schizophrenia and reduce side effects of antipsychotics has been suggested. The aims of this study were to validate the heavier smoking pattern among male schizophrenia patients and to investigate the possible mechanisms for the association. To enhance the reliability of the study, we recruited two large independent samples with 604 and 535 male Chinese schizophrenia patients, and compared their smoking pattern with that of 535 healthy male controls recruited from general population. Validated multiple indicators and multiple causes structure equation model and regression models were used to investigate the association of smoking with factors of schizophrenia symptomatology and with the usage of antipsychotics and their extra-pyramidal side effects (EPS). Schizophrenia patients had significantly heavier smoking pattern compared with healthy controls in our sample (42.4% vs. 16.8%, p<0.001 for current smoking prevalence; 23.5% vs. 43.3%, p<0.001 for smoking cessation rate; 24.5% vs. 3.0%, p<0.001 for heavy smoker proportion). Their smoking status was also found to be consistently and significantly associated with reduced negative factor scores for schizophrenia symptomatology (β = −0.123, p = 0.051 for sample-A; β = −0.103, p = 0.035 for sample-B; β = −0.082, p = 0.017 for the combined sample). However, no significant association was found between smoking and antipsychotics usage or risk of EPS. These results support that smoking is associated with improved negative symptoms, which could account for the heavier smoking pattern among schizophrenia patients.     

Functional Anatomy of Polycomb and Trithorax Chromatin Landscapes in Drosophila Embryos

Polycomb group (PcG) and trithorax group (trxG) proteins are conserved chromatin factors that regulate key developmental genes throughout development. In Drosophila, PcG and trxG factors bind to regulatory DNA elements called PcG and trxG response elements (PREs and TREs). Several DNA binding proteins have been suggested to recruit PcG proteins to PREs, but the DNA sequences necessary and sufficient to define PREs are largely unknown. Here, we used chromatin immunoprecipitation (ChIP) on chip assays to map the chromosomal distribution of Drosophila PcG proteins, the N- and C-terminal fragments of the Trithorax (TRX) protein and four candidate DNA-binding factors for PcG recruitment. In addition, we mapped histone modifications associated with PcG-dependent silencing and TRX-mediated activation. PcG proteins colocalize in large regions that may be defined as polycomb domains and colocalize with recruiters to form several hundreds of putative PREs. Strikingly, the majority of PcG recruiter binding sites are associated with H3K4me3 and not with PcG binding, suggesting that recruiter proteins have a dual function in activation as well as silencing. One major discriminant between activation and silencing is the strong binding of Pleiohomeotic (PHO) to silenced regions, whereas its homolog Pleiohomeotic-like (PHOL) binds preferentially to active promoters. In addition, the C-terminal fragment of TRX (TRX-C) showed high affinity to PcG binding sites, whereas the N-terminal fragment (TRX-N) bound mainly to active promoter regions trimethylated on H3K4. Our results indicate that DNA binding proteins serve as platforms to assist PcG and trxG binding. Furthermore, several DNA sequence features discriminate between PcG- and TRX-N–bound regions, indicating that underlying DNA sequence contains critical information to drive PREs and TREs towards silencing or activation.     

Comparative analysis of protein unfoldedness in human housekeeping and non-housekeeping proteins

Absence of any regular structure is increasingly being observed in structural studies of proteins. These disordered regions or random coils, which have been observed under physiological conditions, are indicators of protein plasticity. The wide variety of interactions possible due to the flexibility of these 'natively disordered' regions confers functional advantage to the protein and the organism in general. This concept is underscored by the increasing proportion of intrinsically unstructured proteins seen with the ascension in the complexity of the organisms. The 'natively unfolded/disordered' state of the protein can be predicted utilizing Uversky's or Dunker's algorithm. We utilized Uversky's prediction scheme and based on the unique position of a protein in the charge-hydrophobicity plot, a derived net score was used to predict the overall disorder of the human housekeeping and non-housekeeping proteins. Substantial numbers of proteins in both the classes were predicted to be unfolded. However, comparative genomic analysis of predicted unfolded Homo sapiens proteins with homologues in Caenorhabditis elegans, Drosophila melanogaster and Mus musculus revealed significant increase in unfoldedness in non-housekeeping proteins in comparison with housekeeping proteins. Our analysis in the evolutionary context suggests addition or substitution of amino acid residues which favour unfoldedness in non-housekeeping proteins compared to housekeeping proteins.     

CD80 binding polyproline helical peptide inhibits T cell activation

The critical role played by the CD28/CD152-CD80/CD86 costimulatory molecules in mediating T cell activation and suppression provides attractive targets for therapeutic strategies. CD28 and CD152 share a conserved polyproline motif in the ligand-binding region. Similar proline-rich regions in globular domains preferentially adopt a polyproline type II (PP) helical conformation and are involved in transient (II)protein-protein interactions. Interestingly, in the human CD80-CD152 complex, Pro(102) of CD152 restricts the preceding proline to PP(II) helix in the binding orientation in relation to the shallow binding pocket of CD80. Peptide agents derived from binding sites of receptors that mimic the bioactive conformation have been shown to block receptor-ligand interactions. Contact preferences of the interface amino acids at the protein-protein interaction sites and the propensity of each residue to form PP(II) helix were integrated in the design of novel peptide agents referred to as CD80 competitive antagonist peptides. Structural and functional studies suggest potential therapeutic value for select CD80 competitive antagonist peptides.