Mechanisms and Regulation of Integumental Organic Solute Transport

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It is increasingly apparent that the integument of aquatic animals can play an active role in mediating the exchange of organic compounds between animals and environment. In this project, the PI will compare the mechanisms of integumental and intestinal nutrient transport. This will represent the first study integrating the characteristics of organic solute transport in these nutrient gathering organs; and include an expansion of their observation of an apparent homology between glucose transporters in invertebrate integument and vertebrate intestine. They will also examine for the first time the regulatory influence of two significant environmental factors, salinity and nutrient availability. This is particulary exciting given the recent observation that the quaternary nitrogenous compound, betaine, is avidly transported by the integument; characterization of this transporter, which has not been reported in any epithelial system, could have an important impact on current studies of the role of betaine and related compounds in vertebrate and invertebrate osmoregulation. Finally, the PI proposes to begin study of the development of integument transport, including the mechanism of transport activation that occurs upon fertilization. The approach in all these studies will be to combine the use of intact animals, isolated tissues, and preparations of subcellular membranes, along with the introduction to this work of several recently introduced molecular probes for transport proteins as well as use of NMR as a tool for studying changes in the physical nature of intracellular solutes. The proposed work also includes a comparative examination of integumental and intestinal nutrient transport in two major phyla, the Mollusca and Echinodermata. The proposed work examines the regulation of nutrient uptake by several different organ systems in aquatic organisms. The studies include the first examination of the molecular basis of the activation of nutrient uptake into newly fertilized eggs, and then follows the development of particular aspects of these processes from egg to the nutrient acquiring organs of the adult. These results should be directly applicable to the understanding if optimal growing conditions for several species of commercially important shellfish.