Carbon dioxide, pH and bicarbonate sensing in sharks

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

All organisms must be able to sense and regulate the levels of acidity (low pH) and alkalinity (high pH) in their internal fluids. However, the mechanisms by which organisms sense acidity and alkalinity are not well understood. Sharks undergo pronounced variations in blood pH as part of their normal physiology, and therefore are excellent models to study mechanisms for pH sensing and regulation. This project will use biochemical, molecular, cell biology, and physiological tools to determine how sharks sense changes in pH and to characterize downstream regulatory processes. This information will help us understand and predict how organisms respond to environmental and metabolic stress. Because this project will focus on cellular pathways that are shared with other organisms, the results will also be applicable to a broad array of additional subject areas. Additionally, some of the information will be incorporated into undergraduate and graduate physiology courses taught at UCSD. This project will train one postdoctoral researcher and one minority graduate student in biological research, as well as several undergraduate students. To reach the general public, this project will establish a partnership with Birch Aquarium at Scripps to build awareness of shark biology, ecology and conservation issues through an innovative interpretive internship program for high school students. This project will focus in the bicarbonate-sensing enzyme soluble adenylyl cyclase (sAC), and in putative pH-sensing G-protein coupled receptors associated with transmembrane adenylyl cyclases (GPCR/tmAC). Using a combination of experimental techniques over the entire complexity spectrum from molecules to cells to live sharks, the proposed research will: 1) identify pharmacological inhibitors selective for sAC and tmACs, for their use in cell and whole-organism experiments in this project as well as by other researchers; 2) characterize the mechanisms of sAC and GPCR/tmAC stimulation in shark cells in response to internal and external carbon dioxide, pH and bicarbonate stimuli; and 3) explore the presence of sAC in the cell nucleus and its role in regulating gene expression, using a combination of experiments with isolated nuclei, cells and organs, and transcriptomic and proteomic analyses on tissue samples from starved. This project will characterize reagents and generate testable hypothesis for future physiological and interdisciplinary studies. Results will be disseminated through journals, conferences, and public databases such as NCBI.