Acts as a glycogen-targeting subunit for PP1 and regulates its activity. Activates glycogen synthase, reduces glycogen phosphorylase activity and limits glycogen breakdown. Interacts with PPP1CC catalytic subunit of PP1 and associates with glycogen. Forms complexes with glycogen phosphorylase, glycogen synthase and phosphorylase kinase which is necessary for its regulation of PP1 activity. Ubiquitously expressed in the examined tissues including brain, muscle, liver and spleen under normoxic condition. Its expression is higher in insulin sensitive tissues (liver and muscle) than in the brain and spleen. Significantly increased expression in the liver and muscle under short-term (1-12 hours) hypoxia exposure. Significantly increased expression after long-term (natural) hypoxia exposure in liver and spleen. No significant differences in expression in brain for any time periods. Expression is up-regulated by hypoxia-inducible factor (HIF) under hypoxic conditions. The N-terminal region is required for binding to PP1, the central region is required for binding to glycogen and the C-terminal region is required for binding to glycogen phosphorylase, glycogen synthase and phosphorylase kinase.