Conantokins: developing pharmacology for differentiating N-Methyl-D-Aspartate receptor subtypes

N-methyl-D-aspartate (NMDA) receptors are members of the ionotropic glutamate receptor family that have critical functions in neural plasticity as well as a number of nervous system pathologies. NMDA receptors have a great deal of diversity in the subtypes expressed in different regions of the nervous system throughout the course of development. A greater understanding of NMDA receptor functioning in the nervous system is therefore highly desirable to researchers and clinicians, but this understanding is limited by the current set of selective pharmacological tools. The goal of the work in this dissertation is to gain a greater understanding of how highly selective NMDA receptor antagonists can be developed from a distinct group of peptides derived from the venom of marine cone snails known as the Conantokins, natural products that block NMDA receptors in a subtype-selective manner. The work in this dissertation aims to further this objective through three separate approaches. In Chapter 2, a novel conantokin, Conantokin-Br, is functionally characterized, and structure-activity relationship studies are performed to identify sequence determinants of subtype selectivity. In Chapter 3, NMDA receptor NR2 subunit chimeras are generated and used to identify determinants of selectivity towards Conantokin-R and ConantokinRl-B on the glutamate binding subdomains of the NR2 subunits. In Chapter 4 the selective conantokin ConantokinRl-B is used to identify NR2B-containing NMDA receptor subtypes present in dissociated Ventral Respiratory Column cells. In Chapter 5, these results are summarized, and the overall significance of the work is described. It is hoped that the experiments performed in this work will one day lead to highly selective compounds that will further the frontiers of investigating the underlying functions and therapeutic potential of targeting NMDA receptors.