HUMAN TYROSINE HYDROXYLASE AND SCHIZOPHRENIA

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This is a revised application for competitive renewal of K02 support for Dr. John W. Haycock. This award will enable Dr. Haycock to continue his scientific development and to pursue his recently funded research program (MH55208) on brain monoaminergic systems in mental illnesses, which was initiated and developed over the course of the current award. The ability to study clinical issues related to catecholamine function concurrently with his previously established fundamental neuroscience research program (NS25134) has realized one of the candidate's major long-term goals. As a result, the candidate's short-term goals are focused upon development of his laboratory by recruiting younger scientists to participate in effecting the scientific goals of both the clinical and fundamental research projects. In addition to developing his role as a laboratory director, the candidate will continue his scientific development by pursuing a novel, multidisciplinary approach which he has recently developed, using antibodies to labile epitopes for studying the regulation of signaling molecules in vivo. The proposed research plan focuses upon tyrosine hydroxylase (TyrOH) and tryptophan hydroxylase (TrpOH), which catalyze the initial and rate- limiting steps in catecholamine (dopamine and norepinephrine) and serotonin biosynthesis, respectively. Alterations in each of these systems have been implicated in mental disorders and, in particular, schizophrenia. TyrOH is highly regulated--by protein phosphorylation in the short-term and by transcriptional control in the long-term; and, alternative splicing (which occurs exclusively in monkeys and humans) produces multiple TyrOH isoforms and perhaps, an additional level of regulation. By contrast, comparatively little is known about TrpOH, despite its evolutionary and functional proximity to TyrOH. Postmortem human brain tissue will be analyzed using quantitative blot immunolabeling techniques and a bank of antibodies developed for this purpose by the applicant. TyrOH and TrpOH protein levels, as well as the relative abundances of TyrOH isoforms, will be measured in neurochemically appropriate brain regions dissected from cryostatic sections. DOPA decarboxylase (immediately downstream of both TyrOH and TrpOH) and dopamine beta-hydroxylase (which converts dopamine to norepinephrine) protein levels will also be quantitated, and similar assays have been developed for another class of presynaptic monoaminergic markers--the vesicular and plasmalemmal monoamine transporters. The primary study groups will consist of (a.) suicide/sudden death victims having confirmed diagnoses of schizophrenia and (b.) age-matched, sudden-death control subjects having no Axis 1 mental disorder. Parallel, collaborative studies of major depressives will provide comparison groups and allow identification of potential disease-specific differences.