I plan to study in humans the mechanism of insulin's in vivo regulation of glycogen synthase and protein phosphatase-1 phosphorylation.
Specific Aim I will be the investigation of the site-specific serine phosphorylation that results in activation of the glycogen-binding subunit of protein phosphatase 1, which subsequently dephosphorylates and activates its substrate, glycogen synthase. Glycogen synthase is the final substrate which is activated by insulin to begin glycogenesis.
Specific Aim I l will be extending the same analysis to skeletal muscle in diabetic subjects, and comparing their response to controls which we anticipate will be decreased both basally and after insulin stimulation. The clinical methods used will be a euglycemic insulin clamp, and skeletal muscle biopsies before and at the end of a two hour insulin (or saline) infusion. For analysis of the phosphorylation state of these two enzymes, we will use a new fluorescent-tag technique which allows quantitative analysis of the in vivo changes in the serine phosphorylation pattern of these two key regulatory enzymes. The ability to compare these phosphorylation changes between normal and diabetic subjects will potentially allow for therapeutic interventions designed to normalize the insulin resistance observed in Non-Insulin- Dependent Diabetes Mellitus.
