Some common signaling pathways include: AMPK signaling pathway, cAMP dependent pathway, and insulin signal transduction pathway. AMPK signaling pathway is a fuel sensor and regulator that promotes ATP-production and inhibits ATP-consuming pathways in numerous tissues. AMPK is activated in response to stresses which deplete ATP such as low glucose, heat shock, ischemia, and hypoxia. AMPK activation regulates signaling pathways which replenish cellular ATP. cAMP dependent pathway is a GPCR triggered signaling cascade which is used in cell communication. In this pathway, the activated Gs alpha subunit binds to and activates adenylyl cyclase, which catalyzes the conversion of ATP into cAMP. If the concentration of cAMP increases, it may lead to the activation of cyclic nucleotide-gated ion channels and protein kinase A. The insulin signal transduction pathway is responsible for regulating glucose homeostasis in the body. Insulin travels through the bloodstream and binds to receptors on the surface of cells. As a result, the expression of protein channel GLUT4 on the surface of cells is increased. This allows glucose to move from the bloodstream into cells, lowering blood glucose levels to maintain homeostasis.