Cyclic AMP response element-binding protein in post-mortem brain of teenage suicide victims: specific decrease in the prefrontal cortex but not the hippocampus

Abstract

Abnormalities in both adenylyl cyclase (AC) and phosphoinositide (PI) signalling systems have been observed in the post-mortem brain of suicide victims. Cyclic AMP response element-binding protein (CREB) is a transcription factor that is activated by phosphorylating enzymes such as protein kinase A (PKA) and protein kinase C (PKC), which suggests that both AC and PI signalling systems converge at the level of CREB. CREB is involved in the transcription of many neuronally expressed genes that have been implicated in the pathophysiology of depression and suicide. Since we observed abnormalities of both PKA and PKC in the post-mortem brain of teenage suicide victims, we examined if these abnormalities are also associated with abnormalities of CREB, which is activated by these phosphorylating enzymes. We determined CRE-DNA binding using the gel shift assay, as well as protein expression of CREB using the Western blot technique, and the mRNA expression of CREB using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) technique in the prefrontal cortex (PFC), and hippocampus obtained from 17 teenage suicide victims and 17 matched normal control subjects. We observed that the CRE-DNA binding and the protein expression of CREB were significantly decreased in the PFC of teenage suicide victims compared with controls. There was also a significant decrease in mRNA expression of CREB in the PFC of teenage suicide victims compared with control subjects. However, there were no significant differences in CRE-DNA binding or the protein and mRNA expression of CREB in the hippocampus of teenage suicide victims compared with control subjects. These results suggest that the abnormalities of PKA, and of PKC, observed in teenage suicide victims are also associated with abnormalities of the transcription factor CREB, and that this may also cause alterations of important neuronally expressed genes, and provide further support of the signal transduction of abnormalities in suicide.