The goal of this project is to learn how insulin controls the activity of pyuvate dchydrogenase (PDH). PDH is a metabolic "linch-pin" between energy-yielding processes and biosynthetic pathways, and it therefore plays a key role in the oxidative metabolism of glucose. Most insulin effects result from interactions between insulin and the insulin receptor (IR), which is located on the surfaces of target cells. When insulin binds to the IR, it stimulates the IR to attach phosphate groups to a number of cellular proteins that participate in metabolic reactions. This modification alters the behavior of the targeted proteins - it enhances the activities of some and inhibits the activities of others. But the protein kinase of the IR was not required for the insulin stimulation of PDH activity (preliminary results). Therefore, the specific aim of this proposal is to learn how the insulin receptor communicates with PDH. This will be accomplished by identifying the domains of the insulin receptor that are specifically required for insulin to stimulate PDH. To accomplish this goal, a number of deletion mutations in the insulin receptor will be analyzed for possible effects on insulin stimulation of PDH. Appropriate controls will be performed to verify that the mutant receptors are made in the correct way and to quantitate the numbers of receptors that are expressed at the cell surface, and to ascertain whether the mutations introduce localized or global changes in the confiaguration of the insulin receptor B chain. Global changes could affect a variety of insulin responses, and not just the stimulation of PDH. These studies will provide important information in the mechanism of action of this vital hormone.//
