Figure 3.

CREB expression is regulated via signal transduction pathways Cellular growth factors (GFs) may activate PI3K/AKT or Ras/MEK/ERK pathways when they connect to the membrane-bound receptor. Activation of calcium-dependent kinases increases as Ca²⁺ inflow increases. PKA is turned on when hormone receptors and G-protein-coupled receptors activate adenylate cyclase. All signal transduction pathways may phosphorylate CREB at different serine sites. PKA, protein kinase A; cAMP response element-binding protein, CREB.