Derangements in synaptic transmission are part of the pathology of several neurological and mental diseases including epilepsy, schizophrenia, depression and Alzheimer's disease. The investigator is studying the molecular mechanisms underlying regulation of synaptic transmission. The investigator proposes to study the spatial and temporal regulation at glutamatergic synapses of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and one of its principal postsynaptic substrates, SynGAP. CaMKII is concentrated in glutamatergic neurons in the forebrain and is present in the postsynaptic density where it can be activated by Ca2+ influx through NMDA receptors. The message for alpha-CaMKII is abundant in dendrites in the hippocampus. The investigator has recently found that activation of NMDA receptors produces a long-lasting increase in activated autophosphorylated CaMKII and a rapid rise in CaMKII protein in dendrites. In the first aim, the investigator proposes to use quantitative immunocytochemistry and whole cell patch clamp recordings to study spatial and temporal control of synthesis and autophosphorylation of CaMKII in single neurons in hippocampal slices. The investigator will produce long-term potentiation or long-term depression in single neurons and determine how these and other stimulation paradigms affect the regulation CaMKII throughout the neuron. In the second aim, the investigator proposes to measure the degradation rate of CaMKII in hippocampal slices and determine whether neuronal stimulation alters degradation as well as synthesis of CaMKII in dendrites. SynGAP is a Ras GTPase-activating protein that is concentrated in the postsynaptic density along with CaMKII. The investigator recently found that active CaMKII phosphorylates and inactivates SynGAP's GTPase-activating activity. This inactivation could lead to an increase in active Ras, and thus to an increase in activation of the MAP kinase pathway. The investigator will study the spatial and temporal control of SynGAP by phosphorylation by CaMKII and its link to activation of the MAP kinase pathway by NMDA receptors. In the third aim the amino acid residues on SynGAP that inhibit its GAP activity upon their phosphorylation by CaMKII will be identified. The investigator will then raise phosphosite specific antibodies that recognize the phosphorylated, inhibited form of SynGAP. In the fourth aim, the investigator proposes to use the antibodies to study spatial and temporal regulation of phosphorylation of SynGAP and MAP kinase in hippocampal slices. In the fifth aim, the investigator proposes to create mutant mice lacking SynGAP. The investigator will test the effect of the SynGAP knockout on regulation of the MAP kinase pathway by NMDA receptors.
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