Assess the impact of autophosphorylation on receptor tyrosine kinases in the context of insulin signaling.

• A. Autophosphorylation leads to the degradation of receptor tyrosine kinases, terminating the signal.
• B. Autophosphorylation has no impact on receptor tyrosine kinases or signaling.
• C. Autophosphorylation inhibits receptor tyrosine kinases, preventing further signaling.
• D. Autophosphorylation activates receptor tyrosine kinases, enabling them to phosphorylate downstream targets and propagate the signal.

Answer: (D)