| The nervous system requires efficient and fine-tuned communication. The proper organization of proteins at points of communication is vital for efficient transmission of signals between neurons. Scaffolding proteins, such as PSD95, tether adhesion molecules, receptors, and intracellular signaling enzymes to organize protein complexes that integrate complex signaling. The regulation of receptor insertion and removal alters receptor number at the membrane and controls the signal strength communicated to the post-synaptic neuron. This modification is vital for synaptic plasticity, however, the specific mechanisms involved are not completely understood. Cellular models of synaptic plasticity have also shown the alpha-isoform of Ca2+-calmodulin-dependent kinase II (alphaCaMKII) to be critical. Although alphaCaMKII and synaptic plasticity have been studied in great detail, the mechanism of action is unclear.; Using biochemical techniques, I found that alphaCaMKII increased the interaction of glutamatergic kainate receptors with PSD95. In addition to alphaCaMKII binding PSD95, it phosphorylated and enhanced palmitoylation of PSD95. Additionally, alphaCaMKII activated p38 which also increased the binding of PSD95 to kainate receptors. Using immunocytochemical techniques, I demonstrated that alphaCaMKII increases PSD95 and kainate receptor interactions in heterologous cells and neurons. PSD95 increases the synaptic delivery of kainate receptors, and alphaCaMKII increases the synaptic delivery of PSD95. Additionally, alphaCaMKII increased the density and percentage of synaptically localized PSD95.; Neurons can modulate levels of proteins and regulate synaptic strength by the ubiquitin-proteosome system. Polyubiquitination marks proteins for degradation by proteasomes. I demonstrated that actinfilin interacts with both Cul3 and kainate receptors. These interactions target kainate receptors for degradation by the ubiquitin-proteosome pathway. In addition, actinfilin regulated spine development, possibly through the interaction of actinfilin with Shank and F-actin.; Until now, little has been understood about the regulation of glutamatergic kainate receptors. My thesis work identifies several mechanisms of regulating kainate receptors at the synaptic membrane. |
