Showing papers by "Dennis C. Dean published in 2002"
TL;DR: This co-association of DmGluCl alpha and DmRdl represents the first biochemical and immunological evidence of coassembly of subunits from two different subclasses of ligand-gated ion channel subunits.
Abstract: 35S-labeled derivatives of the insecticides nodulisporic acid and ivermectin were synthesized and demonstrated to bind with high affinity to a population of receptors in Drosophila head membranes that were previously shown to be associated with a glutamate-gated chloride channel. Nodulisporic acid binding was modeled as binding to a single population of receptors. Ivermectin binding was composed of at least two kinetically distinct receptor populations, only one of which was associated with nodulisporic acid binding. The binding of these two ligands was modulated by glutamate, ivermectin, and antagonists of invertebrate gamma-aminobutyric acid (GABA)ergic receptors. Because solubilized nodulisporic acid and ivermectin receptors comigrated as 230-kDa complexes by gel filtration, antisera specific for both the Drosophila glutamate-gated chloride channel subunit GluCl alpha (DmGluCl alpha) and the GABA-gated chloride channel subunit Rdl (DmRdl) proteins were generated and used to examine the possible coassembly of these two subunits within a single receptor complex. DmGluCl alpha antibodies immunoprecipitated all of the ivermectin and nodulisporic acid receptors solubilized by detergent from Drosophila head membranes. DmRdl antibodies also immunoprecipitated all solubilized nodulisporic receptors, but only approximately 70% of the ivermectin receptors. These data suggest that both DmGluCl alpha and DmRdl are components of nodulisporic acid and ivermectin receptors, and that there also exists a distinct class of ivermectin receptors that contains the DmGluCl alpha subunit but not the DmRdl subunit. This co-association of DmGluCl alpha and DmRdl represents the first biochemical and immunological evidence of coassembly of subunits from two different subclasses of ligand-gated ion channel subunits.
103 citations
TL;DR: The findings indicate that the mechanisms by which metal ions and TS2/16 regulate ligand binding to alpha9beta1 and alpha4beta1 are similar, and important differences in their structure and function that can be exploited in the design of selective alpha9 beta1 andalpha4 beta1 inhibitors are identified.
Abstract: Integrins alpha9beta1 and alpha4beta1 form a distinct structural class, but while alpha4beta1 has been subjected to extensive study, alpha9beta1 remains poorly characterized. We have used the small molecule N-(benzenesulfonyl)-(L)-prolyl-(L)-O-(1-pyrrolidinylcarbonyl)tyrosine (3) to investigate the biochemical properties of alpha9beta1 and directly compare these properties with those of alpha4beta1. Compound 3 has a high affinity for both integrins with K(D) values of 1000-fold difference in the affinity of the integrins for VCAM-1, which binds alpha4beta1with an apparent K(D) of 10 nM and alpha9beta1 with an apparent K(D) of >10 microM. Differences were also seen in the binding of alpha9beta1 and alpha4beta1 to osteopontin. Compound 3 competed effectively for the binding of VCAM-1 and osteopontin to both integrins. While these studies show many similarities in the biochemical properties of alpha9beta1 and alpha4beta1, they identify important differences in their structure and function that can be exploited in the design of selective alpha9beta1 and alpha4beta1 inhibitors.
40 citations
TL;DR: A novel, potent nonpeptide oxytocin receptor antagonist (1-1-methylsulfonyl-4-piperidinyloxy) has been identified that can be labeled to high specific activity with [35S].
9 citations
TL;DR: The metabolism of this compound was investigated in rat hepatocytes, and circulating rat plasma metabolites were identified following oral and intravenous dosing, and most intermediates were observed in rat plasma.
Abstract: [3R,5R,6S]-3-(2-cyclopropyloxy-5-trifluoromethoxyphenyl)- 6-phenyl- 1-oxa-7-azaspiro[4.5]decane is a substance P (Neurokinin 1 receptor) antagonist. Substance P antagonists are proven in concept to have excellent potential for the treatment of major depression, and they allow superior and sustained protection from acute and delayed chemotherapy-induced emesis. The metabolism of this compound was investigated in rat hepatocytes, and circulating rat plasma metabolites were identified following oral and intravenous dosing. The turnover in rat hepatocytes within 4 h was about 30%, and the major metabolites were identified as two nitrones and a lactam associated with the piperidine ring. Although these metabolites were also observed in rat plasma, the major circulating metabolite was a keto acid following oxidative de-amination of the piperidine ring. Liquid chromatography/tandem mass spectrometry and nuclear magnetic resonance were used to confirm the structure of the latter metabolite. A mechanism leading to the formation of the keto acid metabolite has been suggested, and most intermediates were observed in rat plasma.
8 citations
TL;DR: In this paper, a reduction of diacid 1 with C2H2O and NaB2H3CN was used to convert it to 7-hydroxymethotrexate (7-OH-MTX).
Abstract: Stable label analogues of methotrexate (MTX) and 7-hydroxymethotrexate (7-OH-MTX) were required for use as internal standards for LC/MS quantitation. A minimum incorporation of stable isotopes to produce a mass increase of 3 in the non-glutamate derived portion of the molecule was necessary for adequate MS detection. The commercial availability of des-methyl MTX (aminopterin, 1) made methylation with C2H3I an attractive option. Surprisingly, all attempted methylations of 1 and the dimethyl ester of 1 failed to provide a significant amount of the methylated aniline, apparently due to attenuated reactivity of the secondary amine towards alkylation. However, reductive amination of diacid 1 with C2H2O and NaB2H3CN gave [C2H3]MTX in 52% yield. A previously reported method was utilized to convert [C2H3]MTX to [C2H3]7-OH-MTX. Preparative HPLC purification of [C2H3]7-OH-MTX resulted in extremely low recovery from the column; this was resolved by switching to a column with few free silanols. Copyright © 2002 John Wiley & Sons, Ltd.
5 citations