How does insulin signaling affect glycogen synthase kinase 3 (GSK3)?

• A. Insulin has no effect on GSK3 activity.
• B. Insulin degrades GSK3 to prevent glycogen formation.
• C. Insulin inactivates GSK3, allowing glycogen synthase to be active.
• D. Insulin activates GSK3, which in turn activates glycogen synthase.

Answer: (C)