TYROSINE HYDROXYLASE AND SCHIZOPHRENIA

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This application for an ADAMHA RSDA (Level II) for Dr. John W. Haycock focuses on the role of brain catecholamine systems in mental health. Dopaminergic systems have been implicated in schizophrenia, and the initial and rate-limiting enzyme in dopamine biosynthesis, tyrosine hydroxylase (TH), will be studied. Transcriptional, translational and posttranslational regulation of TH has been demonstrated in a number of species. Unlike in lower species, however, the messenger RNA encoding TH (mRNA-TH) in humans (and at least one other primate) undergoes alternative splicing, resulting in four different species of human mRNA- TH. In recent work from the applicant's laboratory, protein products corresponding to all four of these mRNA species have been demonstrated in human adrenal medulla whereas in the human and monkey nigrostriatal system, two of the forms predominate. Thus, in humans and primates, alterations in the different isoforms of TH protein may also be involved in the regulation of TH activity. The research proposed in this application involves analysis of the multiple forms of human TH. (A.) Regional, cellular and subcellular distributions of the different forms will be studied with immunoblotting and immunocytochemistry using type-specific antibodies. The regional distribution of the different forms of mRNA-TH and TH protein will be determined in brain samples from schizophrenics and various control groups. (B.) Functional differences between the two major forms will be evaluated by studying the regulation of site-specific TH phosphorylation and TH catalytic activity. Ser31 was identified by Dr. Haycock as a regulated phosphorylation site in TH. In "normally spliced" TH, the phosphorylation of Ser31 has recently been demonstrated by the applicant to be directly mediated by MAP2 kinase whereas in the other form abundant in brain, this serine is within a consensus sequence for phosphorylation by calcium/calmodulin-dependent protein kinase II. Regulation of TH will be studied in situ in human neuroblastoma cell lines and in stably transfected cell lines which express the different forms and in vitro with purified protein kinases and TH purified from the different cell lines. The research development that would be provided by this award includes the progression of Dr. Haycock's extensive fundamental research background into the human/clinical arena. The studies will also provide for the expansion of his areas of expertise into immunocytochemistry and molecular biology. In terms of professional growth, the award will facilitate the concerted efforts necessary to bring his multidisciplinary studies to fruition by preventing further encroachment of departmental and institutional responsibilities into Dr. Haycock's research time. The award would also enhance Dr. Haycock's professional status in terms of consideration for promotion from Associate to Full Professor.