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Edward M Scolnick

Publications and source records attributed to Edward M Scolnick.

12 recordsLinked to original sources
PubMed2006

Analysis of high-resolution HapMap of DTNBP1 (Dysbindin) suggests no consistency between reported common variant associations and schizophrenia.

DTNBP1 was first identified as a putative schizophrenia-susceptibility gene in Irish pedigrees, with a report of association to common genetic variation. Several replication studies have reported confirmation of an association to DTNBP1 in independent European samples; however, reported risk alleles and haplotypes appear to differ between studies, and comparison among studies has been confounded because different marker sets were employed by each group. To facilitate evaluation of existing evidence of association and further work, we supplemented the extensive genotype data, available through the International HapMap Project (HapMap), about DTNBP1 by specifically typing all associated single-nucleotide polymorphisms reported in each of the studies of the Centre d'Etude du Polymorphisme Humain (CEPH)-derived HapMap sample (CEU). Using this high-density reference map, we compared the putative disease-associated haplotype from each study and found that the association studies are inconsistent with regard to the identity of the disease-associated haplotype at DTNBP1. Specifically, all five "replication" studies define a positively associated haplotype that is different from the association originally reported. We further demonstrate that, in all six studies, the European-derived populations studied have haplotype patterns and frequencies that are consistent with HapMap CEU samples (and each other). Thus, it is unlikely that population differences are creating the inconsistency of the association studies. Evidence of association is, at present, equivocal and unsatisfactory. The new dense map of the region may be valuable in more-comprehensive follow-up studies.

Alleles↗
PubMed2006

A cell-based ultra-high-throughput screening assay for identifying inhibitors of D-amino acid oxidase.

Enzymes are often considered less "druggable" targets than ligand-regulated proteins such as G-protein-coupled receptors, ion channels, or other hormone receptors. Reasons for this include cellular location (intracellular vs. cell surface), typically lower affinities for the binding of small molecules compared to ligand-specific receptors, and binding (catalytic) sites that are often charged or highly polar. A practical drawback to the discovery of compounds targeting enzymes is that screening of compound libraries is typically carried out in cell-free activity assays using purified protein in an inherently artificial environment. Cell-based assays, although often arduous to design for enzyme targets, are the preferred discovery tool for the screening of large compound libraries. The authors have recently described a novel cell-based approach to screening for inhibitors of a phosphatase enzyme and now report on the development and implementation of a homogeneous 3456-well plate assay for D-amino acid oxidase (DAO). Human DAO was stably expressed in Chinese hamster ovary (CHO) cells, and its activity was measured as the amount of hydrogen peroxide detected in the growth medium following feeding the cells with D-serine. In less than 12 weeks, the authors proved the concept in 96-and then 384-well formats, miniaturized the assay to the 3456-well (nanoplate) scale, and screened a library containing more than 1 million compounds. They have identified several cell-permeable inhibitors of DAO from this cell-based high-throughput screening, which provided the discovery program with a few novel and attractive lead structures.

Animals↗
PubMed2006

Mechanisms of action of medicines for schizophrenia and bipolar illness: status and limitations.

This paper is not a comprehensive review of the literature. Rather, it is a viewpoint based upon advances in other fields of medicine and genetics that may provide a model for guiding research in psychiatry. The paper discusses the major limitations of the medicines currently used to treat schizophrenia and bipolar illness. The limitations in our understanding of the molecular causes of these two illnesses and our lack of a clear mechanism of action for many of the medicines used to treat them continue to confound the field and impede progress towards finding novel treatments. Until the genetic bases of bipolar illness and schizophrenia are unambiguously identified, progress towards improved diagnosis and treatment will be retarded. An approach to identifying risk genes based upon association studies starting with very large sample sizes based upon currently available diagnoses of bipolar disorder and schizophrenia is advocated.

Antipsychotic Agents↗
PubMed2005

The discovery of a potent and selective lethal factor inhibitor for adjunct therapy of anthrax infection.

A potent and selective anthrax LF inhibitor 40, (2R)-2-[(4-fluoro-3-methylphenyl)sulfonylamino]-N-hydroxy-2-(tetrahydro-2H-pyran-4-yl)acetamide, was identified through SAR study of a high throughput screen lead. It has an IC50 of 54 nM in the enzyme assay and an IC50 of 210 nM in the macrophage cytotoxicity assay. Compound 40 is also effective in vivo in several animal model studies.

Animals↗
PubMed2005

Regulation of gene expression by lithium and depletion of inositol in slices of adult rat cortex.

Lithium inhibits inositol monophosphatase at therapeutically effective concentrations, and it has been hypothesized that depletion of brain inositol levels is an important chemical alteration for lithium's therapeutic efficacy in bipolar disorder. We have employed adult rat cortical slices as a model to investigate the gene regulatory consequences of inositol depletion effected by lithium using cytidine diphosphoryl-diacylglycerol as a functionally relevant biochemical marker to define treatment conditions. Genes coding for the neuropeptide hormone pituitary adenylate cyclase activating polypeptide (PACAP) and the enzyme that processes PACAP's precursor to the mature form, peptidylglycine alpha-amidating monooxygenase, were upregulated by inositol depletion. Previous work has shown that PACAP can increase tyrosine hydroxylase (TH) activity and dopamine release, and we found that the gene for GTP cyclohydrolase, which effectively regulates TH through synthesis of tetrahydrobiopterin, was also upregulated by inositol depletion. We propose that modulation of brain PACAP signaling might represent a new opportunity in the treatment of bipolar disorder.

Animals↗
PubMed2004

High-throughput cell-based screening using scintillation proximity assay for the discovery of inositol phosphatase inhibitors.

Inositol monophosphatase is a potential drug target for developing lithium-mimetic agents for the treatment of bipolar disorder. Enzyme-based assays have been traditionally used in compound screening to identify inositol monophosphatase inhibitors. A cell-based screening assay in which the compound needs to cross the cell membrane before reaching the target enzyme offers a new approach for discovering novel structure leads of the inositol monophosphatase inhibitor. The authors have recently reported a high-throughput measurement of G-protein-coupled receptor activation by determining inositol phosphates in cell extracts using scintillation proximity assay. This cell-based assay has been modified to allow the determination of inositol monophosphatase activity instead of G-protein-coupled receptors. The enzyme is also assayed in its native form and physiological environment. The authors have applied this cell-based assay to the high-throughput screening of a large compound collection and identified several novel inositol monophosphatase inhibitors.

Atropine↗
PubMed2003

N-desmethylclozapine, an allosteric agonist at muscarinic 1 receptor, potentiates N-methyl-D-aspartate receptor activity.

The molecular and neuronal substrates conferring on clozapine its unique and superior efficacy in the treatment of schizophrenia remain elusive. The interaction of clozapine with many G protein-coupled receptors is well documented but less is known about its biologically active metabolite, N-desmethylclozapine. Recent clinical and preclinical evidences of the antipsychotic activity of the muscarinic agonist xanomeline prompted us to investigate the effects of N-desmethylclozapine on cloned human M1-M5 muscarinic receptors. N-desmethylclozapine preferentially bound to M1 muscarinic receptors with an IC50 of 55 nM and was a more potent partial agonist (EC50, 115 nM and 50% of acetylcholine response) at this receptor than clozapine. Furthermore, pharmacological and site-directed mutagenesis studies suggested that N-desmethylclozapine preferentially activated M1 receptors by interacting with a site that does not fully overlap with the acetylcholine orthosteric site. As hypofunction of N-methyl-d-aspartate (NMDA) receptor-driven neuronal ensembles has been implicated in psychotic disorders, the neuronal activity of N-desmethylclozapine was electrophysiologically investigated in hippocampal rat brain slices. N-desmethylclozapine was shown to dose-dependently potentiate NMDA receptor currents in CA1 pyramidal cells by 53% at 100 nM, an effect largely mediated by activation of muscarinic receptors. Altogether, our observations provide direct evidence that the brain penetrant metabolite N-desmethylclozapine is a potent, allosteric agonist at human M1 receptors and is able to potentiate hippocampal NMDA receptor currents through M1 receptor activation. These observations raise the possibility that N-desmethylclozapine contributes to clozapine's clinical activity in schizophrenics through modulation of both muscarinic and glutamatergic neurotransmission.

Allosteric Site↗
PubMed2003

Scintillation proximity assay of inositol phosphates in cell extracts: high-throughput measurement of G-protein-coupled receptor activation.

The phosphatidylinositol turnover assay is used widely to measure activation, and inhibition, of G(q)-linked G-protein-coupled receptors. Cells expressing the receptor of interest are labeled by feeding with tritiated myo-inositol. The label is incorporated into cellular phosphatidylinositol 4,5-bisphosphate, which, upon agonist binding to the receptor, is hydrolyzed by phospholipase C to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol. In the presence of Li(+), dephosphorylation of IP(3) to inositol is blocked, and the mass of soluble inositol phosphates is a quantitative readout of receptor activation. Current protocols for this assay all involve an anion-exchange chromatography step to separate radiolabeled inositol phosphates from radiolabeled inositol, making the assay cumbersome and difficult to automate. We now describe a scintillation proximity assay to measure soluble inositol phosphate mass in cell extracts, thus obviating the need for the standard chromatography step. The method uses positively charged yttrium silicate beads that bind inositol phosphates, but not inositol. We have used this assay to measure activation of recombinant and endogenous muscarinic acetylcholine receptors and activation of recombinant neuropeptide FF2 receptor coupled to IP(3) production by coexpression of a chimeric G protein. Further, we demonstrate the use and functional validity of this assay in a semiautomated, 384-well format, by characterizing the muscarinic receptor antagonists pirenzepine and atropine.

Animals↗
PubMed2002

Developing novel treatments for mood disorders: accelerating discovery.

This review was generated from discussions by the Pharmacologic and Somatic Treatments Section of the National Institute of Mental Health Strategic Plan for Mood Disorders Committee on advancing novel pharmacologic and somatic treatments for mood disorders. The opening section of the article summarizes in broad strokes, current pharmacologic treatments, and new directions in the field. Thereafter the topics focus on specific research initiatives that could advance the current therapeutics for mood disorders including new basic and clinical research in vivo human imaging procedures, somatic therapeutics, and the vast new area of pharmacogenetics. New scientific and technical opportunities exist today based on advances in basic neuroscience, opportunities in clinical testing, industry interest in advancing central nervous system therapeutics, and on active consumer advocacy groups. The question of how to bring all of these positive forces together to accelerate discovery in mood disorder thera-peutics is the topic of this article.

Animals↗
PubMed2002

A peptide-based fluorescence resonance energy transfer assay for Bacillus anthracis lethal factor protease.

A fluorescence resonance energy transfer assay has been developed for monitoring Bacillus anthracis lethal factor (LF) protease activity. A fluorogenic 16-mer peptide based on the known LF protease substrate MEK1 was synthesized and found to be cleaved by the enzyme at the anticipated site. Extension of this work to a fluorogenic 19-mer peptide, derived, in part, from a consensus sequence of known LF protease targets, produced a much better substrate, cleaving approximately 100 times more efficiently. This peptide sequence was modified further on resin to incorporate donor/quencher pairs to generate substrates for use in fluorescence resonance energy transfer-based appearance assays. All peptides cleaved at similar rates with signal/background ranging from 9-16 at 100% turnover. One of these substrates, denoted (Cou)Consensus(K(QSY-35)GG)-NH(2), was selected for additional assay optimization. A plate-based assay requiring only low nanomolar levels of enzyme was developed for screening and inhibitor characterization.

Antigens, Bacterial↗
PubMedDate not supplied

Schizophrenia: do the genetics and neurobiology of neuregulin provide a pathogenesis model?

The sequencing of the human genome and an emerging dense map of markers across the human genome have spawned new approaches to search for risk genes for human diseases with complex genetics. These approaches are particularly relevant to the search for risk genes for bipolar disorder and schizophrenia. A gene called neuregulin 1 has been reported to be a risk gene for schizophrenia. This article reviews aspects of the genetics, cellular neurobiology, and biochemistry of neuregulin 1 and attempts to integrate several observations from disparate fields into a model for the pathogenesis of schizophrenia. The model outlines experimental approaches that may, in the future, shed more light on its validity.

Central Nervous System↗