Egr-1 modulation of synapsin I expression: permissive effect of forskolin via cAMP.
A number of candidate Egr-1 neuronal target genes have been identified including the synapsin I gene. Previous studies have shown that over-expression of Egr-1 in cells transfected with an Egr-1 expression vector is sufficient to activate reporter genes linked to regions of the synapsin I promoter, but any effect on the expression of synapsin I within its genomic context has not been demonstrated. We tested our hypothesis that modulation of synapsin I expression by Egr-1 requires the presence of elevated cAMP which would normally be present during periods of neuronal plasticity. Both the adenyl cyclase activator, forskolin (frsk), and the cAMP analogue, Sp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt (Sp-cAMPS), enhanced the ability of Egr-1 to transactivate a CAT reporter plasmid containing multiple copies of the Egr-1 binding site (EBS). Furthermore, Egr-1 alone had minimal effects on synapsin I expression whereas forskolin treatment of PC12 cells profoundly affected the ability of Egr-1 to regulate synapsin I expression. These results suggest that Egr-1 transactivation during neuronal plasticity may rely on a permissive effect of cAMP.
James
Allan B
AB
Division of Neuroscience and Biomedical Systems, Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow, Scotland G12 8QQ, UK. A.James@bio.gla.ac.uk
Conway
Ann-Marie
AM
Thiel
Gerald
G
Morris
Brian J
BJ
D000818:Animals; D001665:Binding Sites; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D051766:Early Growth Response Protein 1; D004797:Enzyme-Linked Immunosorbent Assay; D017930:Genes, Reporter; D017874:Immediate-Early Proteins / Q000502:physiology*; D016716:PC12 Cells; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism; D016704:Synapsins / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection; D001616:beta-Galactosidase / Q000378:metabolism
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D016704:Synapsins; D014157:Transcription Factors; D005576:Colforsin; D000242:Cyclic AMP; D015500:Chloramphenicol O-Acetyltransferase; D012260:Ribonucleases; D001616:beta-Galactosidase