Inverse regulation of plasticity-related immediate early genes by calcineurin in hippocampal neurons.
In the mammalian hippocampus, changes in the expression of immediate early genes (IEGs) is thought to contribute to long term plastic changes in neurons brought about by learning tasks and high frequency stimulation of synapses. The phosphatase calcineurin has emerged as an important negative regulator of hippocampus-dependent learning and long term potentiation. Here we investigated the possibility that the constraining action of calcineurin on hippocampal plasticity is mediated in part by regulation of gene expression through negative control of transcription factors, such as cAMP-response element (CRE)-binding protein (CREB). We assessed the effect of calcineurin inhibitors on CREB activation by neuronal activity and show that calcineurin activity is in fact required for CREB-mediated gene expression. However, inhibition of calcineurin had disparate effects on the transcriptional induction of CREB-dependent IEGs. We find that the IEG c-fos is unaffected by suppression of calcineurin activity, the plasticity-related genes Egr1/Zif268 and Egr2/Krox-20 are up-regulated, and genes encoding the orphan nuclear hormone receptors Nor1 and Nur77 are down-regulated. We further show that the up-regulation of particular IEGs is probably due to the presence of serum response elements (SREs) in their promoters, because SRE-mediated gene expression is enhanced by calcineurin blockers. Moreover, expression of the c-fos gene, which is unaffected by calcineurin inhibitors, could be down-regulated by mutating the SRE. Conversely, SRE-mediated c-fos induction in the absence of a functional CRE was enhanced by calcineurin inhibitors. Our experiments thus implicate calcineurin as a negative regulator of SRE-dependent neuronal genes.
Lam
Brian Yee Hong
BY
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
Zhang
Wenting
W
Enticknap
Nicola
N
Haggis
Eleanor
E
Cader
M Zaeem
MZ
Chawla
Sangeeta
S
D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis; D051767:Early Growth Response Protein 2 / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D051076:Proto-Oncogene Proteins c-fyn / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D011987:Receptors, Steroid / Q000096:biosynthesis; D027602:Serum Response Element / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; D051767:Early Growth Response Protein 2; C486110:Egr1 protein, rat; C497328:Egr2 protein, rat; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; C539820:Nr4a1 protein, rat; C091333:Nr4a3 protein, rat; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D011987:Receptors, Steroid; D050882:CREB-Binding Protein; C494365:Crebbp protein, rat; D051076:Proto-Oncogene Proteins c-fyn; D019703:Calcineurin