Eag, CaMKII and dCASK: Three interacting proteins involved in synaptic transduction

While there are a great many proteins involved in synaptic function and plasticity, this study focuses on three proteins fulfilling very different tasks in the synapse. Eag (ethera-go-go) is a potassium channel critical to regulating excitability at the synapse. This work not only explores the discovery of an alternate splice variant which lacks the channel domain, but the creation of a splice reporter capable of detecting activation of the splice machinery necessary for the production of this new activity-dependent protein product. CaMKII (calcium/calmodulin dependent protein kinase II) has long been known to be critical in long term potentiation (LTP) and phosphorylates a wide variety of substrates from ion channels including Eag to itself. This work uncovers a new property of CaMKII -- the ability of the protein to use GTP as well as ATP as a phosphate donor for substrate and autophosphorylation. This new and rather unique ability may add another dimension to regulation of this important protein in synaptic plasticity. The final phase of this work includes both of these proteins in combination with a scaffolding protein, dCASK, which is known to increase Eag current by recruiting new channels to the membrane, and to regulate the activity state of CaMKII by increasing phosphorylation at a site critical to calcium activation. This work shows that dCASK is not synaptically localized in the basal condition, but that activity, whether acute or prolonged, relocates dCASK to the synapse. Alternately, although dCASK is an important regulator of CaMKII activity, loss of the dCASK protein does not affect pre- or postsynaptic localization of CaMKII to the synapse. Together, these projects explore several means by which molecules may play a role in synaptic plasticity.