Insulin receptors are proteins found on the surfaces of most cells in the human body. Insulin binding activates it and triggers a signaling cascade inside the cell, resulting in glucose uptake and various other metabolic and growth-related functions. Insulin receptor uses IRS proteins to activate PI3-kinase. Activated insulin receptor binds transiently IRS proteins, which becomes phosphorylated and thereafter bind the regulatory subunits (p85) of PI3-kinase.