MUSCLE GLYCOGEN-SYNTHASE TRANSLOCATES FROM THE CELL-NUCLEUS TO THE CYTOSOL IN RESPONSE TO GLUCOSE

We have studied the intracellular localization of muscular glycogen sy nthase by fusing the green fluorescent protein (GFP) of the jelly-fish Aequorea victoria to the N-terminus of human muscle glycogen synthase (HMGS), and expressing the chimeric protein in C2C12, COS-1 cells, an d primary cultured rat hepatocytes. In contrast to what rye have recen tly found for the hepatic glycogen synthase (Fernandez-Novell et al. ( 1997) Biochem. J. 321, 227-231), the GFP/HMGS fusion protein is locali zed to the nucleus of the cell in the absence of glucose, and in the p resence of the sugar it is essentially found in the cytosol. Insulin i s not required for the translocation of the enzyme. (C) 1997 Federatio n of European Biochemical Societies.