Doctor of Philosophy

dissertationHeterotrimeric G-protein signaling pathways modulate synaptic transmission in response to secreted factors. For example, Go, the most abundant G protein in the nervous system, negatively regulates neuron activity by acting on potassium channels and calcium channels in mammalian systems, although it is possible that other pathways may exist. In my thesis, I used a genetic approach in the nematode C. elegans to study the neuronal function of Go. I identified an activated Go mutant, which was then used to screen for downstream components of Go signaling. Several of the proteins I identified in my screen regulate neuronal excitability, including activation of the calcium- and voltage-activated potassium channel SLO-1, and the gap junction component innexin UNC-9, and inactivation of the novel ion channel NCA-1. Further genetic screens demonstrated that the NCA-1 channel requires accessory subunits UNC-79 and UNC-80. A functional channel complex can be reconstituted by expressing NCA-1, UNC-79 and UNC-80 in Xenopus oocytes. The channel forms a sodium-selective, voltage-dependent current. I propose a model in which Go and Gq converge on the RhoGEF UNC-73B and Go downregulates NCA-1 activity by antagonizing Gq activation of this pathway