Low GSK-3 activity in frontal cortex of schizophrenic patients

Glycogen synthase kinase-3 (GSK-3) (EC 2.7.1.37) is a protein kinase highly abundant in brain and involved in signal transduction cascades of multiple cellular processes, particularly neurodevelopment. Two forms of the enzyme , GSK-3 alpha and -3 beta have been previously identified. We have previous ly reported reduced GSK-3 beta protein levels in postmortem frontal cortex of schizophrenic patients. In an attempt to explore whether reduction of GS K-3 beta levels is brain region specific we examined it in occipital cortex . In order to find out if the reduction in frontal cortex is reflected in a ltered activity we measured GSK-3 enzymatic activity in this brain region. Western-blot analysis of GSK-3 beta was carried out in postmortem occipital cortex of 15 schizophrenic, 15 bipolar, and 15 unipolar patients, and 15 n ormal controls. GSK-3 activity was measured by quantitating the phosphoryla tion of the specific substrate phospho-CREB in the frontal cortex specimens . GSK-3 beta levels in occipital cortex did not differ between the four dia gnostic groups. GSK-3 activity in the frontal cortex of schizophrenic patie nts was 45% lower than that of normal controls (0.196 +/- 0.082 and 0.357 /- 0.084 pmol/mg protein X min, respectively; Kruskal-Wallis analysis: chi- square = 8.27, df = 3, p = 0.04). The other two diagnostic groups showed no difference from the control group. Our results are consistent with the not ion that schizophrenia involves neurodevelopmental pathology. (C) 2001 Else vier Science B.V. All rights reserved.