Further evidence for a membrane receptor that binds glucocorticoids in the rodent hypothalamus.
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 BS3and 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 Kd4-24-fold lower and a Bmax4-7-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.
Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, United States.
Jebun
J
Nahar
Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, United States.
Jennifer R
JR
Rainville
Department of Psychology, Tulane University, New Orleans, LA 70118, United States; Neuroscience Program, Tulane University, New Orleans, LA 70118, United States.
Gary P
GP
Dohanich
Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, United States; Neuroscience Program, Tulane University, New Orleans, LA 70118, United States. Electronic address: tasker@tulane.edu.
Jeffrey G
JG
Tasker
D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D003907:Dexamethasone / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D011485:Protein Binding; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D003345:Corticosterone
Corticosteroid; Glucocorticoid receptor; HPA; Hypothalamus; Membrane cross-linking; Stress