Very low levels of the glucocorticoid receptor beta isoform in the human hippocampus as shown by Taqman RT-PCR and immunocytochemistry.
The hippocampus is an important target for glucocorticoid hormones. Glucocorticoid receptor (GR) mediated feedback in this area is important for control of behavioural adaptation. An alternative splice variant, the GRbeta (GRbeta) isoform, does not bind ligand and has been proposed to inhibit classic GRalpha-mediated transactivation of target genes. Hence, an increased ratio of GRbeta to GRalpha may induce relative corticosteroid-resistance, as e.g. presumed to occur in major depression. To investigate whether GRbeta is involved in the human hippocampus, we studied GRalpha and GRbeta expression levels in postmortem hippocampal tissue of control subjects by quantitative PCR (Taqman RT-PCR) and immunocytochemistry. Taqman RT-PCR demonstrated a very low relative abundance of GRbeta in the human hippocampus (GRalpha:GRbeta ratio approximately 14,500:1). Immunohistochemical analysis confirmed the occurrence of isolated profiles indeed displaying nuclear staining in the main hippocampal subregions. Subsequent double immunofluorescent analysis revealed that >98% of these GRbeta positive cells were double positive for leucocyte common antigen, that identifies exclusively blood-derived cells of haematopoietic origin, including microglia. We conclude that GRbeta is present in very low amounts in the control human hippocampus, and that of these low numbers of cells, notably, almost all are derived from blood which is inevitably present in postmortem tissue. A functionally relevant role for the GRbeta in control of the human hippocampus is therefore not very likely. Whether this is altered in disease conditions awaits further research.
DeRijk
Roel H
RH
Division of Medical Pharmacology, Leiden University, 2300 RA Leiden, The Netherlands. rderijk@rijngeestgroep.nl
Schaaf
Marcel
M
Stam
Floor J
FJ
de Jong
Inge E M
IE
Swaab
Dick F
DF
Ravid
Rivka
R
Vreugdenhil
Erno
E
Cidlowski
John A
JA
de Kloet
E Ron
ER
Lucassen
Paul J
PJ
D000368:Aged; D015152:Blotting, Northern; D002452:Cell Count; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007962:Leukocytes / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D011956:Receptors, Cell Surface / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019914:Taq Polymerase; D014158:Transcription, Genetic
D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011965:Receptors, Glucocorticoid; C411470:glucocorticoid receptor alpha; C121943:glucocorticoid receptor beta; D019914:Taq Polymerase; C516772:PTPRF protein, human; D017027:Protein Tyrosine Phosphatases; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2