Figure 5.

Hypothetical model depicting the possible role of ZGM-associated G_αi3 in regulation of secretory vesicle swelling and fusion at the plasma membrane in pancreatic acinar cells. In the presence of GTP, the G_αi3 protein is activated by replacement of its GDP with GTP, resulting in the opening of ZGM-associated Cl⁻ and K⁺ channels. There is then a net increase in flow of Cl⁻ and K⁺ ions together with water molecules into the ZG lumen, resulting in vesicle swelling and subsequent fusion at the plasma membrane by an unknown mechanism.