Designing novel inhibitors against falcipain-2 of Plasmodium falciparum

Coumarin containing pyrazoline derivatives have been synthesized and tested as inhibitors of in vitro development of a chloroquine-sensitive (MRC-02) and chloroquine-resistant (RKL-2) strain of Plasmodium falciparum and in vivo Plasmodium berghei malaria. Docking study was also done on cysteine protease falcipain-2 which showed that the binding pose of C-14 molecule and epoxysuccinate, inhibitor of falcipain-2, binds in the similar pattern. The most active antimalarial compound was 3-(1-benzoyl-5-(4-flurophenyl)-4,5-dihydro-1H-pyrazol-3yl)-7-(diethyamino)-2H-chromen-2-one C-14, with an IC₅₀ of 4.21?µg/ml provided complete protection to the infected mice at 24?mg/kg X 4?days respectively.     

Reconstitution of a functional human type II IL-4/IL-13 receptor in mouse B cells: demonstration of species specificity

IL-13 is a Th2-derived pleiotropic cytokine that recently was shown to be a key mediator of allergic asthma. IL-13 mediates its effects via a complex receptor system, which includes the IL-4R alpha-chain, IL-4Ralpha, and at least two other cell surface proteins, IL-13Ralpha1 and IL-13Ralpha2, which specifically bind IL-13. IL-13 has been reported to have very limited effects on mouse B cells. It was unclear whether this was due to a lack of receptor expression, a disproportionate relative expression of the receptor components, or an additional subunit requirement in B cells. To determine the requirements for IL-13 signaling in murine B cells, we examined IL-13-dependent Stat6 activation and CD23 induction in the murine B cell line, A201.1. A201.1 cells responded to murine IL-4 via the type I IL-4R, but were unresponsive to IL-13, and did not express IL-13 receptor. B220(+) splenocytes also failed to signal in response to IL-13 and did not express IL-13 receptor. We transfected A201.1 cells with human IL-4Ralpha, IL-13Ralpha1, or both. Transfectants expressing either human IL-4Ralpha or human IL-13Ralpha1 alone were unable to respond or signal to IL-13. Thus, human IL-13Ralpha1 could not combine with the endogenous murine IL-4Ralpha to generate a functional IL-13R. However, cells transfected with both human IL-4Ralpha and IL-13Ralpha1 responded to IL-13. Thus, the relative lack of IL-13 responsiveness in murine B cells is due to a lack of receptor expression. Furthermore, the heterodimeric interaction between IL-4Ralpha and IL-13Ralpha1 is species specific.     

Expression and Purification of Isotopically Enriched MHC Binding Immunogenic Peptides for NMR Studies

Peptides are important naturally occurring ligands of MHC molecules. X-ray crystallographic studies have enabled extensive characterization of such peptide ligands. Yet structural and dynamic changes of these peptides in the MHC bound state are not well understood. These conformational transitions are key to understanding the function of MHC molecules and for the development of peptide-based therapeutics. Employing NMR for such studies can fill this gap but it requires the availability of peptides labeled with NMR-active nuclei. Here we report production of nine-mer MHC-binding peptides for use in high resolution NMR studies. The method utilizes a fusion protein approach of attaching the peptide to an easily expressed bacterial protein. The fusion protein construct design allows for rapid purification of the fusion protein and avoids chemical modification of the peptide as a result of the cleavage reaction. The methods developed here allow for rapid cloning of additional MHC binding peptides without significant molecular biology effort. 8?C10 mg of mature freeze dried peptides can be obtained from 1 liter of minimal media, sufficient for NMR experimentation. Six uniformly ¹⁵N-labeled peptides have been successfully expressed in bacteria and NMR spectra with the expected number of well-resolved signals were recorded. The results obtained here will make peptide-MHC complexes amenable to structural analysis which has not been possible previously.     

Parthenolide sensitizes cells to X-ray-induced cell killing through inhibition of NF-kappaB and split-dose repair

Human cancers have multiple alterations in cell signaling pathways that promote resistance to cytotoxic therapy such as X rays. Parthenolide is a sesquiterpene lactone that has been shown to inhibit several pro-survival cell signaling pathways, induce apoptosis, and enhance chemotherapy-induced cell killing. We investigated whether parthenolide would enhance X-ray-induced cell killing in radiation resistant, NF-kappaB-activated CGL1 cells. Treatment with 5 microM parthenolide for 48 to 72 h inhibited constitutive NF-kappaB binding and cell growth, reduced plating efficiency, and induced apoptosis through stabilization of p53 (TP53), induction of the pro-apoptosis protein BAX, and phosphorylation of BID. Parthenolide also enhanced radiation-induced cell killing, increasing the X-ray sensitivity of CGL1 cells by a dose modification factor of 1.6. Flow cytometry revealed that parthenolide reduced the percentage of X-ray-resistant S-phase cells due to induction of p21 waf1/cip1 (CDKN1A) and the onset of G1/S and G2/M blocks, but depletion of radioresistant S-phase cells does not explain the observed X-ray sensitization. Further studies demonstrated that the enhancement of X-ray-induced cell killing by parthenolide is due to inhibition of split-dose repair.     

Functional correlates of the lateral and medial entorhinal cortex: objects,path integration and local–global reference frames

The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between ‘where’ versus ‘what’ needs revision. We propose a refinement of this model, which is more complex than the simple spatial–non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience.