What occurs during the auto-phosphorylation of the insulin receptor (INSR)?

During the auto-phosphorylation of the insulin receptor, the receptor itself undergoes a critical modification that leads to the phosphorylation of tyrosine residues within its own cytoplasmic domain. This auto-phosphorylation event is essential for the activation of the receptor after it binds insulin. Once the insulin receptor is phosphorylated, it undergoes a conformational change, which activates its intrinsic tyrosine kinase activity.

This activated receptor is now capable of phosphorylating downstream target proteins, which are crucial for mediating the cellular effects of insulin, such as glucose uptake, lipid synthesis, and glycogen synthesis. The specificity of the signal and the propagation of the insulin signaling pathway are greatly enhanced because the phosphorylated receptor can interact with various signaling molecules, facilitating broader cellular responses.

The other options do not reflect the primary role of auto-phosphorylation in this context. Deactivation of protein kinase A (PKA), activation of phosphatases, and inhibition of adenylyl cyclase are not direct outcomes of the auto-phosphorylation of the insulin receptor. Instead, they reflect broader regulatory mechanisms within cells that may involve different signaling pathways outside the immediate consequence of the insulin receptor's auto-phosphorylation.