Brain region specific alterations in the protein and mRNA levels of protein kinase A subunits in the post-mortem brain of teenage suicide victims

Protein kinase A (PKA), a critical component of the adenylyl cyclase signaling system, phosphorylates crucial proteins and has been implicated in the pathophysiology of depression and suicide. The objective of the study was to examine if changes in PKA activity or in the protein and messenger RNA (mRNA) expression of any of its subunits are related to the pathophysiology of teenage suicide. We determined PKA activity and the protein and mRNA expression of different subunits of PKA in cytosol and membrane fractions obtained from the prefrontal cortex, (PFC) hippocampus, and nucleus accumbens (NA) of post-mortem brain from 17 teenage suicide victims and 17 nonpsychiatric control subjects. PKA activity was significantly decreased in the PFC but not the hippocampus of teenage suicide victims as compared with controls. However, the protein and mRNA expression of only two PKA subunits, that is, PKA RI alpha and PKA RI beta, but not any other subunits were significantly decreased in both membrane and cytosol fractions of the PFC and protein expression of RI alpha and RI beta in the NA of teenage suicide victims as compared to controls. A decrease in protein and mRNA expression of two specific PKA subunits may be associated with the pathogenesis of teenage suicide, and this decrease may be brain region specific, which may be related to the specific behavioral functions associated with these brain areas. Whether these changes in PKA subunits are related to suicidal behavior or are a result of suicide or are specific to suicide is not clear at this point.