Cell membrane signals in the mechanism of insulin action. Claude P. Brown memorial lecture.

Present evidence points to the rapid formation of one or several mediators by proteolysis initiated by insulin and, possibly, other hormones. Mediators act intracellularly at a number of subcellular sites, including cytoplasm, mitochondria, endoplasmic reticulum, cell membrane, and nucleus (figure 9). These mediators control enzymes that are controlled by covalent phosphorylation. As a result, the mediators impart an overall integrated control of metabolism. Evidence strongly suggests that the mediators are peptides. They appear to be formed by limited proteolysis from cell membrane proteins or glycoproteins and act as transmembrane signals following the binding of insulin to its receptor and the activation of the insulin-receptor complex.