Further evidence for a membrane receptor that binds glucocorticoids in the rodent hypothalamus

• Published in: Steroids Vol. 114; pp. 33 - 40
• Main Authors: Nahar, Jebun, Rainville, Jennifer R., Dohanich, Gary P., Tasker, Jeffrey G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2016
• Subjects: Animals; Blotting, Western; Cell Membrane - metabolism; Corticosteroid; Corticosterone - metabolism; Cytosol - metabolism; Dexamethasone - metabolism; Glucocorticoid receptor; Glucocorticoids - metabolism; HPA; Hypothalamus; Hypothalamus - metabolism; In Vitro Techniques; Male; Membrane cross-linking; Mice; Protein Binding; Rats; Receptors, Glucocorticoid - metabolism; Stress; Membrane cross-linking; HPA; Corticosteroid; Hypothalamus; Stress; Glucocorticoid receptor
• ISSN: 0039-128X; 1878-5867
• DOI: 10.1016/j.steroids.2016.05.013

•Evidence is presented for a membrane glucocorticoid receptor.•Glucocorticoid receptor immunoreactive bands are membrane-associated.•Glucocorticoids bind to rodent hypothalamic membrane fraction. In parallel with their well-characterized delayed genomic effects, steroid hormones exhibit rapid, non-genomic effects at molecular, cellular and behavioral levels. We have proposed a model of rapid, non-genomic glucocorticoid inhibition of hypothalamic neuroendocrine cells through a putative membrane-associated glucocorticoid receptor (GR). Here we tested for plasma membrane GR immunoreactivity and binding in the hypothalamic supraoptic and paraventricular nuclei. Selective cross-linking of membrane proteins with membrane-impermeant BS3 and subsequent Western blot analysis with a monoclonal GR antibody revealed a reduction in the intensities of a ∼98kDa immunoreactive band and a ∼64kDa band in the rat paraventricular and supraoptic nuclei, and of a 64kDa band in hippocampal tissue, which suggested that these proteins are associated with the membrane. Saturation binding of [3H]-corticosterone and [3H]-dexamethasone in rat and mouse hypothalamic tissue revealed a Kd 4–24-fold lower and a Bmax 4–7-fold lower for the membrane-associated GR compared to the intracellular GR, suggesting a lower affinity and abundance of the glucocorticoid binding sites in the membrane than in the cytosol. Together, these findings suggest the presence of a low-affinity, low-abundance membrane-associated GR in the hypothalamus that shares homology with the intracellular GR, and are consistent with physiological evidence of rapid, non-genomic glucocorticoid actions in hypothalamic neuroendocrine cells that are GR dependent.