No abstract

The tumour suppressor p53 is the most frequently mutated gene in human cancer. Reactivation of mutant p53 by small molecules is an exciting potential cancer therapy. Although several compounds restore wild-type function to mutant p53, their binding sites and mechanisms of action are elusive. Here computational methods identify a transiently open binding pocket between loop L1 and sheet S3 of the p53 core domain. Mutation of residue Cys124, located at the centre of the pocket, abolishes p53 reactivation of mutant R175H by PRIMA-1, a known reactivation compound. Ensemble-based virtual screening against this newly revealed pocket selects stictic acid as a potential p53 reactivation compound. In human osteosarcoma cells, stictic acid exhibits dose-dependent reactivation of p21 expression for mutant R175H more strongly than does PRIMA-1. These results indicate the L1/S3 pocket as a target for pharmaceutical reactivation of p53 mutants.

Cyanobacteria (blue-green algae) (e.g., Microcystis and Nodularia spp.) capable of producing toxic peptides are found in fresh and brackish water worldwide. These toxins include the microcystin (MC) heptapeptides (>60 congeners) and the nodularin pentapeptides (ca. 5 congeners). Cyanobacterial cyclic peptide toxins are harmful to man, other mammals, birds, and fish. Acute exposure to high concentrations of these toxins causes liver damage, while subchronic or chronic exposure may promote liver tumor formation. The detection of cyclic peptide cyanobacterial toxins in surface and drinking waters has been hampered by the low limits of detection required and that the present routine detection is restricted to a few of the congeners. The unusual -amino acid ADDA (4E,6E-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid) is present in most (>80%) of the known toxic penta-and heptapeptide toxin congeners. Here, we report the synthesis of two ADDA-haptens, the raising of antibodies to ADDA, and the development of a competitive indirect ELISA for the detection of microcystins and nodularins utilizing these antibodies. The assay has a limit of quantitation of 0.02-0.07 ng/mL (depending on which congeners are present), lower than the WHO-proposed guideline (1 ng/mL) for drinking water, irrespective of the sample matrix (raw water, drinking water, or pure toxin in PBS). This new ELISA is robust, can be performed without sample preconcentration, detects toxins in freshwater samples at lower concentrations than does the protein phosphatase inhibition assay, and shows very good cross-reactivity with all cyanobacterial cyclic peptide toxin congeners tested to date (MC-LR, -RR, -YR, -LW, -LF, 3-desmethyl-MC-LR, 3-desmethyl-MC-RR, and nodularin).

Neuropeptide S (NPS) has been shown to modulate arousal, sleep wakefulness, anxiety-like behavior, and feeding after central administration of the peptide agonist to mice or rats. We report here the chemical synthesis and pharmacological characterization of SHA 66 (3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid benzylamide) and SHA 68 (3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide), two closely related bicyclic piperazines with antagonistic properties at the NPS receptor (NPSR). The compounds block NPS-induced Ca 2ϩ mobilization, and SHA 68 shows displaceable binding to NPSR in the nanomolar range. The antagonistic activity of SHA 68 seems to be specific because it does not affect signaling at 14 unrelated G protein-coupled receptors. Analysis of pharmacokinetic parameters of SHA 68 demonstrates that the compound reaches pharmacologically relevant levels in plasma and brain after i.p. administration. Furthermore, peripheral administration of SHA 68 in mice (50 mg/kg i.p.) is able to antagonize NPSinduced horizontal and vertical activity as well as stereotypic behavior. Therefore, SHA 68 could be a useful tool to characterize physiological functions and pharmacological parameters of the NPS system in vitro and in vivo.Neuropeptide S (NPS) and its receptor, NPSR, are a recently identified transmitter system that modulates a number of brain functions . NPS is a small peptide of 20 amino acids that occurs in all tetrapod vertebrates but is absent from fish (Reinscheid, 2007). Activation of NPSR produces transient increases in intracellular Ca 2ϩ and cAMP and thus increases cellular excitability (Reinscheid et al., 2005). Expression of NPS precursors and receptors is found in specific brain areas that have been associated with arousal, emotional processing, energy, and hormonal homeostasis, as well as learning and memory (Xu et al., 2004(Xu et al., , 2007. In the rat, NPS precursor transcripts are expressed in only a few brainstem structures; in particular, in a previously uncharacterized nucleus situated between the noradrenergic locus coeruleus and Barrington's nucleus. Besides the pericoerulear region, NPS mRNA is only found in the lateral parabrachial nucleus and the principle sensory 5 nucleus of the rat brainstem. A few scattered cells expressing NPS precursor transcripts are also detected in the amygdala and hypothalamus. In the brainstem, the majority of NPSexpressing neurons coexpress other excitatory transmitters, such as glutamate, acetylcholine, or corticotropin-releasing factor (Xu et al., 2007). NPSR mRNA is found at high levels in hypothalamus, thalamus, amygdala, various cortical regions, and the parahippocampal formation. Central administration of NPS was shown to produce profound arousal that is independent of novelty (Xu et al., 2004).

No abstract

No abstract

In order to determine the conformational requirements for binding of L-glutamate to the proteins involved in the process of neurotransmission, rigid analogues containing an embedded glutamate moiety have been prepared. These "conformer mimics", the pyrrolidine-2,4-dicarboxylates 4, 7, 11, and 14, were synthesized from commercially available trans-4-hydroxy-L-proline and cis-4-hydroxy-D-proline, and then were tested for their ability to inhibit the high-affinity transport of [3H]-L-glutamate into synaptosomes and to block the binding of radioligands to the NMDA (N-methyl-D-aspartate), KA (kainate), and QA (quisqualate) glutamate neurotransmitter receptor sites. While none of the four analogues binds effectively to the excitatory receptors, the L-trans-isomer 7 is a potent and selective competitive inhibitor of L-glutamate transport. These results delineate a specific structural/conformational preference for binding to the uptake system that is distinct from that required for binding to the NMDA, KA, and QA receptors.

No abstract