1,4,9,10-Anthradiquinone as precursor for antitumor compounds

1,4,9,10-Anthradiquinone 5 was reacted with enamines 6 in the Nenitzescu reaction to yield unexpected 3,3a,6,12-tetrahydro-3a,7-dihydroxy-2-methyl-6,12-dioxo-naphtho[2,3-d]indol-1-carboxylates 8A. However, anthracycline-like naphtho-condensed 5-hydroxyindoles were not obtained from this diquinone. It yielded similar reaction products of the Nenitzescu reaction like other quinones activated by two electron-withdrawing groups. Furthermore, these new compounds 8A were found to constitute precursors for the synthesis of azonines. The conversion to dibenzoazonines 13 occurred in an unusual and up to now unknown way consisting of isomerization, ring opening, and re-closure. 2-Chloro-anthradiquinone 19 reacted with enamines 6 as vinylogeous acid chloride to pyrroloanthraquinone 20. No substitution of chlorine was observed. Naphtho-condensed indoles 26 were obtained by the reactions of unsubstituted 1,4-anthraquinone 25 with enamines 6 via the normal Nenitzescu route. Indoles 26 were converted to Mannich bases, reacting further to dimers by the Diels-Alder reaction of intermediate o-quinone methides. Most of the synthesized heterocycles were evaluated for their anticancer properties in the NCI's human-disease oriented in vitro anticancer screen. Particularly, carbinolamines 8A exhibited inhibitory activity of tumor cell growth and thus they constitute a new class of lead structures for anticancer drug design.     

Relations in biomedical ontologies

To enhance the treatment of relations in biomedical ontologies we advance a methodology for providing consistent and unambiguous formal definitions of the relational expressions used in such ontologies in a way designed to assist developers and users in avoiding errors in coding and annotation. The resulting Relation Ontology can promote interoperability of ontologies and support new types of automated reasoning about the spatial and temporal dimensions of biological and medical phenomena.     

Membrane insertion of the mannitol permease of Escherichia coli occurs under conditions of impaired SecA function.

The membrane insertion of the mannitol permease (MtlA protein) of Escherichia coli, a polytopic cytoplasmic membrane protein possessing an uncleaved amphiphilic signal sequence, was studied using a cell-free protein synthesis system. The MtlA protein synthesized in the presence of inside-out cytoplasmic membrane vesicles was shown to insert into the membranes based on the following criteria: (a) co-sedimentation of the majority of the MtlA protein with the vesicles; (b) selective extraction of the membrane-associated MtlA by doxycholate but not by urea treatment; and (c) protease resistance of a defined MtlA fragment observed exclusively in the presence of membranes. Post-translational addition of membrane vesicles allowed membrane association of MtlA but did not allow efficient integration. In cell-free systems having reduced levels of the export factors SecA and SecB and exhibiting defective translocation of preOmpA and preLamB, insertion of the in vitro synthesized MtlA apparently occurred normally. In contrast, when membranes from the secY24ts mutant or trypsin-treated membranes were used, insertion of MtlA was reduced. In vivo experiments monitoring the permease activity of MtlA in the secA and secY mutants supported the conclusions of the in vitro results. Thus, the insertion of MtlA is essentially SecA- and SecB-independent but may be dependent on SecY and/or an as yet unidentified membrane protein. The requirements for the insertion of the mannitol permease are therefore clearly different from those for the translocation of most proteins having a cleavable hydrophobic signal sequence.     

Insulin resistance due to phosphorylation of insulin receptor substrate-1 at serine 302

Inhibitory serine phosphorylation is a potential molecular mechanism for insulin resistance. We have developed a new variant of the yeast two-hybrid method, referred to as disruptive yeast tri-hybrid (Y3H), to identify inhibitory kinases and sites of phosphorylation in insulin receptors (IR) and IR substrates, IRS-1. Using IR and IRS-1 as bait and prey, respectively, and c-Jun NH(2)-terminal kinase (JNK1) as the disruptor, we now show that phosphorylation of IRS-1 Ser-307, a previously identified site, is necessary but not sufficient for JNK1-mediated disruption of IR/IRS-1 binding. We further identify a new phosphorylation site, Ser-302, and show that this too is necessary for JNK1-mediated disruption. Seven additional kinases potentially linked to insulin resistance similarly block IR/IRS-1 binding in the disruptive Y3H, but through distinct Ser-302- and Ser-307-independent mechanisms. Phosphospecific antibodies that recognize sequences surrounding Ser(P)-302 or Ser(P)-307 were used to determine whether the sites were phosphorylated under relevant conditions. Phosphorylation was promoted at both sites in Fao hepatoma cells by reagents known to promote Ser/Thr phosphorylation, including the phorbol ester phorbol 12-myristate 13-acetate, anisomycin, calyculin A, and insulin. The antibodies further showed that Ser(P)-302 and Ser(P)-307 are increased in animal models of obesity and insulin resistance, including genetically obese ob/ob mice, diet-induced obesity, and upon induction of hyperinsulinemia. These findings demonstrate that phosphorylation at both Ser-302 and Ser-307 is necessary for JNK1-mediated inhibition of the IR/IRS-1 interaction and that Ser-302 and Ser-307 are phosphorylated in parallel in cultured cells and in vivo under conditions that lead to insulin resistance.