This proposal is intended to contribute to an understanding of the intracellular transduction of the insulin signal and the regulation of cellular metabolism in general. A comprehension of insulin action is necessary to develop new methods of diagnosing and treating diabetes mellitus. The general aims of the study are to characterize the interactions among the insulin receptor, casein kinase II (a multipoten- tial serine/threonine kinase) and calmodulin. Calmodulin, an intracel- lular mediator of Ca 2+ signals, is phosphorylated in vitro by both the insulin receptor kinase and casein kinase II and recent evidence suggests that casein kinase II is involved in the cellular mechanism of insulin action. It is my hypothesis that the phosphorylation of calmodulin by casein kinase II and the insulin receptor kinase represents an important point of cross-talk between the two signalling pathways. The proposed studies include the following specific aims: 1) Characterization of calmodulin phosphorylation in intact cells and the effects of insulin and casein kinase II on this process; 2) Investigation of the physiological consequences of calmodulin phosphorylation; Together these studies should provide definitive information on the role of calmodulin and casein kinase II in insulin action and also add to our knowledge of the intracellular transduction of the insulin signal; 3) Investigation of the alteration of substrate specificity of the insulin receptor produced by calmodulin prephosphorylated by casein kinase II. This includes investigating the altered interaction between phosphocalmodulin and the insulin receptor and characterizing the receptor associated, insulin-- stimulated serine/threonine kinase; and 4) Characterization of the sequential phosphorylation of calmodulin by casein kinase II and the insulin receptor in vitro. The influence of multiple sites of phosphorylation on each other and the effect of other growth factors will also be examined.
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