Ligand gated ion channels are a family of proteins that act as switches, which convert chemical signals to electrical signals in nerve cells. Acid sensing channels, a member of this family of proteins, are transmembrane proteins that bind to protons and open channels that are specific for cations. They not only play a critical role in neurotransmission in higher vertebrates but also play a role in mediating sensory responses proteins in lower vertebrates such as worms, flies, hydra, and sea urchins which have proteins with similar sequences. A recent structure of one type of the acid sensing channel indicates that the mechanism by which this protein responds to protons (lower pH) is by the protonation of acidic residues present on the extracellular side of this protein. The proposed project will test this hypothesis and establish if these residues are indeed the sensors for the acidic pH. For these studies the vibrations of the acidic residues will be investigated to determine if they are protonated at the pH where the protein functions. In addition, the proposed research will also determine the structural changes initiated by protonation that ultimately leads to the formation of the cation channel. To study these large scale structural changes in the protein the investigator will attach fluorescent probes at specific sites, and determine distances between the probes by measuring the extent of energy transfer from one site to the other. The changes at specific carboxylate residues and the large scale structural changes will then be contextualized in terms of electrical measurements that allow for characterization of the opening and closing of the cation channels. This multi-scale structural and functional study should provide a comprehensive understanding of the mechanism of chemical to electrical signal transmission in these proteins.
Broader Impacts This project will also address the broader impacts criterion defined by NSF. Training both undergraduate and graduate students in methods relevant to a better understanding and utilization of the synergistic areas of chemistry and neuroscience will continue to be a focus of the proposed project. The goal of the training is to reinforce students' interest in science, develop technical and critical thinking, and improve their communication skills. An additional goal in the training will be to continue our efforts to promote the participation of underrepresented minorities and women in science. We have been successful in training several minority students and women in the lab, with the most recent minority graduate student obtaining her doctoral degree last spring. Finally, the broader impact on society of the proposed project will be through the training of future scientists in cutting edge interdisciplinary research that covers various aspects of science.