The study of protein turnover in insects has the potential for development into a unique nonmammalian model system. Initial studies will include development of methodology for measuring protein turnover in vivo in flight and intersegmental muscles. The specific time course of turnover of these protein pools will be followed. Little is known also about the regulation of the turnover of major larval hemolymph proteins or the role of the amino acids derived from their breakdown. This research will also consider role(s) and control of the turnover of these proteins in manduca sexta. Several investigators have suggested that these proteins may function as storage proteins for supplying amino acids for the synthesis of new protein (e.g., in flight muscle and cuticle) during metamorphosis. Studies will focus on the fate of amino acids derived from the breakdown of these proteins by injecting radiolabeled arylphorin (manducin), produced in young larvae, into developing animals. The fate of 14C-amino acid provided directly to the hemolymph will be studied for comparisons. Specific activities of amino acids will be measured in intracellular pools and tissue proteins. These data will show the potential interrelationship between amino acids of storage proteins, hemolymph and tissue pools. The potential role of ecdysteroid in changes in turnover of these various protein pools (i.e., muscle, arylphorin) will be considered. Future work will consider the potential contribution of protease activities and inhibitors in controlling the turnover of proteins in the fat body.
