This is a project to study biochemical events in the early stages of detection of chemicals by odor receptors. The project will be directed by Dr. Richard Bruch, who will be using catfish as the organism under study and amino acids as the odorants. The reasons are that the olfactory receptors of catfish are conveniently accessible and much is known about their physiological properties. Amino acids are natural components of foods for catfish, and they have evolved sensitive and specific receptors for them. The information about basic mechanisms obtained from this study is expected to find application in other organisms and for other odorous chemicals. Dr. Bruch's basic hypothesis is that there are specific receptor proteins for amino acids in catfish olfactory receptor cell ciliary membranes, and that when these proteins interact with amino acids the protein/amino acid complex somehow initiates a particular series of biochemical reactions. These involve the participation of a so-called "G-protein" (a protein that binds a guanine nucleotide) and leads to increased metabolism of a certain class of membrane lipids, the phosphoinositides. He will test this hypothesis by measuring binding of radioactive amino acids to proteins from the cilia in an attempt to demonstrate that the receptor proteins really exist. He will measure phosphinositide turnover upon amino acid stimulation, including the effects of added guanine nucleotides and of modifiers of the G-protein. He will also study the regulation of the enzyme, phospholipase C, which initiates phosphoinositide turnover, and attempt to determine its location in the cell. This project hold the promise of contributing greatly to our understanding of transduction in olfactory receptor cells and in sensory cells in general.
