Characterization of a novel membrane glucocorticoid receptor
Description
Several lines of evidence indicate that glucocorticoids exert not only delayed effects but also rapid non-genomic effects at molecular, cellular and behavioral levels. Like other steroid hormones, glucocorticoids are well known to use intracellular receptors that bind DNA in a sequence-specific manner to modulate transcriptional activity of target genes. However, increasing circumstantial evidence from pharmacological, electrophysiological, and behavioral experiments has accumulated over recent years supporting the concept of a rapid, non-genomic, non-genotropic action of glucocorticoids both in peripheral tissues and in the central nervous system. The overall objective of this research proposal is to provide further support for and to further characterize the putative membrane glucocorticoid receptor (mbGR) that is thought to mediate the rapid non-genomic actions of glucocorticoids in the mammalian hypothalamus. The supporting experiments described in this proposal include electrophysiological, biochemical, pharmacological, and molecular techniques to characterize the neuronal mbGR in pursuit molecular identification. The data obtained in this study provides new insight into the location, antigenicity, binding affinity, and abundance of the mbGR in rat and mouse hypothalamic and hippocampal tissue. Data suggest the presence of a low affinity, low abundant mbGR that shows antigenic cross reactivity with intracellular GR and a positive modulatory effect with Mg2+. The results also support the presence of a rapid glucocorticoid effect model in mice hypothalamic neurons, where the mbGR and CB1 endocannabinoid receptors play important role. Acute application of dexamethasone and dexamethasone conjugated BSA shows up and down regulation of proteins involved in several biological pathways. Dihydropyriminidase-related protein 2 is identified as a component of the complex membrane GR and/or its signal transduction mechanism. There is no quantitative alteration of GR-immunoreactive bands following various stress conditions compared to the nonstressed group, suggesting alteration at pathways downstream to the ligand-receptor complex