Which of the following sequences correctly describes the insulin signaling pathway via RTKs?

• A. Insulin binds to RTK, IP3 is produced, calcium is released, leading to increased glucose metabolism
• B. Insulin binds to RTK, DAG is produced, PKC is activated, leading to increased glycogen synthesis
• C. Insulin binds to RTK, IRS-1 is phosphorylated, PI3K is activated, leading to increased GLUT4 expression
• D. Insulin binds to RTK, cAMP is produced, PKA is activated, leading to increased glucose uptake

Answer: (C)