One of the most important mechanisms for regulating neuronal function is through second messenger cascades that regulate protein kinases. Ca2+/calmodulin-dependent protein kinase 2 (designated CK2) is the most abundant protein kinase in mammalian brain and its alpha-subunit is the major protein and enzymatic component of synaptic junctions. CK2 has been implicated in diverse CNS processes such as epilepsy, sensory deprivation, ischemia, synapse formation, synaptic transmission and learning and memory. The goal of our studies is to understand the molecular and cellular and mechanisms underlying the involvement of CK2 in neuronal differentiation and synaptic function. The injection of specific inhibitors of CK2 into hippocampal neurons blocks the induction of long-term potentiation (LTP), a popular cellular model of learning and memory. Our current hypothesis is that the function CK2 in LTP induction is to phosphorylate critical postsynaptic proteins which are responsible for triggering long-term increases in synaptic strength. Our first specific aim is to identify and functionally characterize postsynaptic proteins that are phosphorylated by CK2; these experiments will involve protein phosphorylation, microsequencing and eventually recombinant DNA cloning. We will also determine how the phosphorylation of these proteins is regulated during synaptic stimulation. Recent findings have determined that the mRNA encoding the alpha-subunit of CK2 is one of a few neuronal mRNAs localized in dendrites, the specialized postsynaptic compartments which receive and integrate information. The second specific aim is to elucidate the molecular and cellular mechanisms responsible for targeting specific messenger RNAs to dendrites. We will use the alpha-mRNA as a model in these studies. Current speculation suggests that the localized translation of dendritic mRNAs encoding specific synaptic proteins may be responsible for producing synapse-specific associated with the processing, storage and retrieval of information in neurons. During brain development the expression of the alpha-subunit of CK2 coincides with the most active period of synapse formation, whereas the expression of its Beta-subunit is not regulated in the same developmental or brain region specific manner. Our third specific goal focuses on the identification and functional characterization of genomic elements and regulatory factors that control the expression of the alpha-subunit of CK2 in developing neurons and the mature CNS. New information obtained in these experiments is expected to provide insights into the cellular, molecular and genetic mechanisms that regulate an important protein kinase involved in synapse formation, and the modifiability of synaptic functions in the mammalian brain.
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