salicylates and daidzein

The facilitative hexose transporter GLUT1 is a multifunctional protein that transports hexoses and dehydroascorbic acid, the oxidized form of vitamin C, and interacts with several molecules structurally unrelated to the transported substrates. Here we analyzed in detail the interaction of GLUT1 with a group of tyrosine kinase inhibitors that include natural products of the family of flavones and isoflavones and synthetic compounds such as the tyrphostins. These compounds inhibited, in a dose-dependent manner, the transport of hexoses and dehydroascorbic acid in human myeloid HL-60 cells, in transfected Chinese hamster ovary cells overexpressing GLUT1, and in normal human erythrocytes, and blocked the glucose-displaceable binding of cytochalasin B to GLUT1 in erythrocyte ghosts. Kinetic analysis of transport data indicated that only tyrosine kinase inhibitors with specificity for ATP binding sites inhibited the transport activity of GLUT1 in a competitive manner. In contrast, those inhibitors that are competitive with tyrosine but not with ATP failed to inhibit hexose uptake or did so in a noncompetitive manner. These results, together with recent evidence demonstrating that GLUT1 is a nucleotide binding protein, support the concept that the inhibitory effect on transport is related to the direct interaction of the inhibitors with GLUT1. We conclude that predicted nucleotide-binding motifs present in GLUT1 are important for the interaction of the tyrosine kinase inhibitors with the transporter and may participate directly in the binding transport of substrates by GLUT1.

Topics: Adenosine Triphosphate; Animals; Binding, Competitive; CHO Cells; Cinnamates; Cricetinae; Enzyme Inhibitors; Flavonoids; Genistein; Glucose Transporter Type 1; Hexoses; HL-60 Cells; Humans; Isoflavones; meta-Aminobenzoates; Monosaccharide Transport Proteins; Phenols; Protein Binding; Protein-Tyrosine Kinases; Quercetin; Salicylates; Substrate Specificity; Tyrosine; Tyrphostins

The N-methyl-D-aspartate (NMDA) receptor contributes to synaptic plasticity in the central nervous system and is both serine-threonine and tyrosine phosphorylated. In CA1 pyramidal neurons of the hippocampus, activators of protein kinase C (PKC) as well as the G-protein-coupled receptor ligands muscarine and lysophosphatidic acid enhanced NMDA-evoked currents. Unexpectedly, this effect was blocked by inhibitors of tyrosine kinases, including a Src required sequence and an antibody selective for Src itself. In neurons from mice lacking c-Src, PKC-dependent upregulation was absent. Thus, G-protein-coupled receptors can regulate NMDA receptor function indirectly through a PKC-dependent activation of the non-receptor tyrosine kinase (Src) signaling cascade.

Topics: Alkaloids; Amino Acid Sequence; Animals; Benzophenanthridines; Cells, Cultured; Enzyme Activation; Enzyme Inhibitors; Genistein; GTP-Binding Proteins; Isoflavones; Lysophospholipids; meta-Aminobenzoates; Mice; Mice, Knockout; Microinjections; Molecular Sequence Data; Muscarine; Nerve Tissue Proteins; Neuronal Plasticity; Oocytes; Patch-Clamp Techniques; Phenanthridines; Phenols; Phosphorylation; Protein Kinase C; Protein Processing, Post-Translational; Proto-Oncogene Proteins pp60(c-src); Pyramidal Cells; Rats; Rats, Wistar; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Lysophosphatidic Acid; Receptors, Muscarinic; Receptors, N-Methyl-D-Aspartate; Salicylates; Signal Transduction; Tetradecanoylphorbol Acetate; Xenopus laevis