Heterodimerization of mineralocorticoid and glucocorticoid receptors at a novel negative response element of the 5-HT1A receptor gene.
Negative regulation of neuronal serotonin (5-HT1A) receptor levels by glucocorticoids in vivo may contribute to depression. Both types I (mineralocorticoid) and II (glucocorticoid) receptors (MR and GR, respectively) participate in corticosteroid-induced transcriptional repression of the 5-HT1A gene; however, the precise mechanism is unclear. A direct repeat 6-base pair glucocorticoid response element (GRE) half-site 5'-TGTCCT separated by 6 nucleotides was conserved in human, mouse, and rat 5-HT1A receptor promoters. In SN-48 neuronal cells that express MR, GR, and 5-HT1A receptors, deletion or inactivation of the nGRE (negative GRE) eliminated negative regulation of the rat 5-HT1A or heterologous promoters by corticosteroids, whereas its inclusion conferred corticosteroid-induced inhibition to a heterologous promoter. Bacterially expressed recombinant MR and GR preferentially bound to the nGRE as a heterodimer, as identified in nuclear extracts of MR/GR-transfected COS-7 cells, and with higher affinity than MR or GR homodimers. In SN48 and COS-7 cells, concentration-dependent coactivation of MR and GR was required for maximal inhibitory action by corticosteroids and was abrogated in the L501P-GR mutant lacking DNA binding activity. Corticosteroid-mediated transcriptional inhibition was greater for MR/GR in combination than for MR or GR alone. These data represent the first identification of an nMRE/GRE and indicate that heterodimerization of MR and GR mediates direct corticosteroid-induced transrepression of the 5-HT1A receptor promoter.
Neuroscience Research Institute, University of Ottawa, Ottawa, Ontario K1H-8M5, Canada.
X M
XM
Ou
J M
JM
Storring
N
N
Kushwaha
P R
PR
Albert
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D017353:Gene Deletion; D005938:Glucocorticoids / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D051379:Mice; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000737:chemistry*; D018161:Receptors, Mineralocorticoid / Q000737:chemistry*; D011985:Receptors, Serotonin / Q000235:genetics*; D044263:Receptors, Serotonin, 5-HT1; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020218:Response Elements; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D003907:Dexamethasone; D005982:Glutathione Transferase; D003850:Deoxyribonuclease I