The protein p130, named from its molecular size, was originally identified as an inositol 1, 4,5-trisphosphate binding protein similar to phospholipase C (PLC)-δ1, but lacking any PLC activity. It was recently renamed PLC-related catalytically inactive protein-1 (PRIP-1). In the present study, PRIP-1 gene-targeted mice were analyzed for glycogen metabolism based on the previous finding that PRIP-1 interacts with protein phosphatase-1 (26). Compared to the control mice, mutant mice exhibited lower phosphorylase activity and higher levels of glycogen in the liver, which appeared to be consistent with the inhibition of protein phosphatase-1 by PRIP-1. These observation could also be attributed to the increased levels of plasma insulin. Hyperinsulinemia, observed even in the young mice, was progressive with aging, and was accompanied by the accumulation of fat tissues, increased body weight and decreased sensitivity to insulin in the mutant mice at the age of 12 months. These results suggest that PRIP-1 is a molecule involved in the control of plasma insulin.
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