insulinreceptor

The insulin receptor is a transmembrane protein that plays a crucial role in regulating blood glucose levels. It belongs to the receptor tyrosine kinase family. The receptor is a heterotetramer composed of two extracellular alpha subunits and two transmembrane beta subunits, linked by disulfide bonds.

When insulin binds to the alpha subunits on the outer surface of the cell membrane, it causes a conformational change in the receptor. This change activates the intracellular tyrosine kinase domain of the beta subunits. The activated kinase then phosphorylates specific tyrosine residues on itself (autophosphorylation) and on downstream signaling proteins.

This phosphorylation cascade initiates a series of intracellular events. Key among these is the activation of phosphatidylinositol 3-kinase (PI3K), which in turn triggers pathways that promote glucose uptake into cells, particularly in muscle and adipose tissue, by facilitating the translocation of GLUT4 glucose transporters to the cell surface. Other effects of insulin receptor activation include the promotion of glycogen synthesis, inhibition of gluconeogenesis, and regulation of lipid and protein metabolism.

Dysfunction of the insulin receptor, whether due to genetic mutations or acquired changes, can lead to insulin resistance, a condition where cells do not respond effectively to insulin. This is a hallmark of type 2 diabetes and can also contribute to other metabolic disorders. Conversely, mutations leading to a hyperactive insulin receptor can cause hypoglycemia.