Figure 1.

Scheme of the insulin signal transduction pathways. Insulin acts on target cells through its specific insulin membrane receptor (IR). IR consists of two α subunits located outside the cell membrane and two β subunits anchored to the cell membrane. Activation of the IR causes autophosphorylation of the β subunits, which recruit the next cellular proteins. Insulin activates two major signal transduction pathways: the PI3K-PKB/Akt-dependent pathway and the MAPK (mitogen-activated protein kinase) kinase pathway.