Abnormal protein phosphorylation in post-mortem brain tissue from bipolar patients

Abnormal phosphorylation has been proposed to be involved in the pathogenesis of affective disorders. The present study investigated basal and cAMP-stimulated endogenous protein phosphorylation in human postmortem brain tissue from bipolar and schizophrenic patients. Furthermore, basal kinase activity and stimulated protein kinase A activity were measured. The frontal and occipital cortex were analysed. Using [γ-³²P]ATP as phosphate donor, basal and cAMP-stimulated phosphorylation of endogenous proteins was measured in the absence or presence of 8-Br-cAMP, respectively. The proteins were separated on SDS-gels and the radioactivity in the individual bands was measured. We observed a significant reduction of ³²P incorporation in three protein substrates (15, 16 and 21 kD) in frontal cortex of bipolar patients. However, there were no differences in the PKA activity between any of the groups. The present study demonstrates abnormal phosphorylation of specific proteins in brain tissue obtained from bipolar patients in comparison to schizophrenics and controls.