Physiological and Molecular Characterization of Ca Pump and Exchanger; an Integrated Approach Modeled on the Freshwater Crayfish Molting Cycle

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9603723 Wheatly The mineral calcium (abbreviated Ca) is of fundamental biological importance. In animals it is a component of biominerals such as skeleton and shell. It is also necessary for muscle contraction and for relaying messages from the exterior to the interior of the cell. For these reasons, scientists are very interested in how Ca moves between different parts of the body and specifically how it is transported across cell membranes (boundaries). These processes are easily modeled in crustaceans (aquatic arthropods) for two reasons. First their calcium carbonate skeleton is external and therefore far more accessible than the backbone of vertebrates. More importantly, in order to grow, they undergo the molting cycle which involves Ca cycling out of and into the animal. In preparation for molting, Ca is reabsorbed from the old skeleton and either recycled or lost (Ca leaves). Once the old skeleton is shed, the animal must rapidly mineralize the new skeleton (calcium enters). Calcium leaves/enters via specialized layers of cells (epithelia) that communicate either directly or indirectly with the external water. The calcium exchanging surfaces include gill, kidney and gut. Ca movement across these cells is effected by specialized proteins situated in the cell membrane. Manufacture of specific proteins is under the control of genetic material (termed DNA) in the nucleus of the cell. In this grant, the PI proposes to use the crustacean molting cycle to (1) study the dynamics of Ca transport across vesicles (resealed patches of cell membrane akin to a water balloon) and to (2) isolate the DNA that codes for the Ca pumping proteins and to assess whether abundance of the DNA is regulated by steroids. These studies will enable understanding of the evolution of Ca transporting proteins common to all cells. ***