What is the role of GRB2 in insulin signaling, and how does it interact with IRS 1?

• A. GRB2 binds to phosphorylated IRS 1 via its SH2 domain, linking it to downstream signaling molecules.
• B. GRB2 inhibits IRS 1 by binding to it, preventing further signaling.
• C. GRB2 dephosphorylates IRS 1, terminating the signal.
• D. GRB2 phosphorylates IRS 1, enhancing its signaling capacity.

Answer: (A)