[Classification of mutations in the insulin receptor gene]

Mutations in the insulin receptor gene can cause insulin resistance by interfering with a step (s) in the life cycle of the insulin receptor. These steps include biosynthesis, posttranslational modifications and transport to plasma membrane, ligand binding, trans membrane signaling, and endocytosis, recycling and degradation. Mutations are functionally classified into five classes: mutations that decrease the rate of receptor biosynthesis (class I), mutations that impair intracellular transport and post-translational processing (class II), mutations that cause defects in insulin binding (class III), mutations that impair receptor tyrosine kinase activity (class IV), and mutations that accelerate receptor degradation (class V). Examples of insulin receptor gene mutations for each of these five classes are shown.