BRAIN CALMODULIN-DEPENDENT PROTEIN KINASE

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We are interested in the molecular structure and function of synaptic connections between neurons in the central nervous system. Derangements in the regulation of these connections are an important part of the pathology of several neurological and mental diseases including epilepsy, Alzheimer's disease, Huntington's chorea, schizophrenia, and depression. Many neurotransmitters and neurohormones regulate synaptic function by altering intracellular levels of calcium ion. We are studying the mechanisms by which these fluctuations in calcium levels alter synaptic function. We will focus our studies primarily on the molecular characterization and cellular localization of a synaptic regulatory pathway that has as its central element and abundant, brain-specific calcium and calmodulin-dependent protein kinase. This enzyme is composed of two types of subunits that share certain chemical characteristics, but appear to be present in different ratios in different regions of the brain. We will compare the structure and function of the two subunits by biochemical and recombinant DNA methods. We will also compare the distributions of both subunits in different brain nuclei, quantitatively by radiommunoassay, as well as by immunohistochemistry. We will determine whether neurons containing the kinase are associated with particular transmitter systems or specific anatomical pathways. Biochemical experiments suggest that the kinase is a component of certain brain postsynaptic densities and may also be associated with synaptic vesicles and microtubules. We will determine the subcellular locations of both kinase subunits in different brain regions by biochemical and immunochemical methods and by electron microscopic immunohistochemistry. Focusing on the hippocampus, where kinase activity is most highly concentrated, we will examine the proteins that are phosphorylated by the kinase in brain slices and in homogenates. Our long term goal is two-fold. First, we want to understand the functions of this calcium-mediated regulatory pathway. Second, we want to correlate information about it with similar information about other calcium-regulated pathways (e.g. calcium-dependent adenylate cyclase, phosphodiesterase, phosphatases, etc.), in order to understand the concerted responses to changing calcium levels in CNS neurons.