FIGURE 2.

Regulation loop between insulin secreting and target cells. In beta cells, insulin can be secreted in the circulation by glucose, NT and also by the propeptide (PE) likely through its interaction with NTSR2 or the potassium channel TREK-1 through NTSR3. In insulin target cells, the activation of insulin receptor by insulin leads to the Akt-dependent translocation of Glut4/NTSR3/sortilin containing vesicles to the plasma membrane where the propeptide can be released in the circulation. This loop of regulation between insulin secreting and insulin target cells is likely involved in fine tuning of glucose homeostasis.