The Journal of biological chemistry
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Critical role for GATA3 in mediating Tie2 expression and function in large vessel endothelial cells.
Endothelial phenotypes are highly regulated in space and time by both transcriptional and post-transcriptional mechanisms. There is increasing evidence that the GATA family of transcription factors function as signal transducers, coupling changes in the extracellular environment to changes in downstream target gene expression. Here we show that human primary endothelial cells derived from large blood vessels express GATA2, -3, and -6. ⋯ GATA3 knockdown blocked the ability of Ang-1 to attenuate vascular endothelial cell growth factor stimulation of vascular cell adhesion molecule-1 expression and monocytic cell adhesion. Moreover, exposure of human umbilical vein endothelial cells to tumor necrosis factor-alpha resulted in marked down-regulation of GATA3 expression and reduction in Tie2 expression. Together, these findings suggest that GATA3 is indispensable for Ang-1-Tie2-mediated signaling in large vessel endothelial cells.
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The present study tests the hypothesis that the structure of extracellular domain Loop 2 can markedly affect ethanol sensitivity in glycine receptors (GlyRs) and gamma-aminobutyric acid type A receptors (GABA(A)Rs). To test this, we mutated Loop 2 in the alpha1 subunit of GlyRs and in the gamma subunit of alpha1beta2gamma2GABA(A)Rs and measured the sensitivity of wild type and mutant receptors expressed in Xenopus oocytes to agonist, ethanol, and other agents using two-electrode voltage clamp. Replacing Loop 2 of alpha1GlyR subunits with Loop 2 from the deltaGABA(A)R (deltaL2), but not the gammaGABA(A)R subunit, reduced ethanol threshold and increased the degree of ethanol potentiation without altering general receptor function. ⋯ The deltaL2 mutations did not affect GlyR or GABA(A)R sensitivity, respectively, to Zn(2+) or diazepam, which suggests that these deltaL2-induced changes in ethanol sensitivity do not extend to all allosteric modulators and may be specific for ethanol or ethanol-like agents. To explore molecular mechanisms underlying these results, we threaded the WT and deltaL2 GlyR sequences onto the x-ray structure of the bacterial Gloeobacter violaceus pentameric ligand-gated ion channel homologue (GLIC). In addition to being the first GlyR model threaded on GLIC, the juxtaposition of the two structures led to a possible mechanistic explanation for the effects of ethanol on GlyR-based on changes in Loop 2 structure.