Figure 6. Role of G alpha Inhibitory Protein. (A) – cells with normally functioning G alpha inhibitory protein (Gai-2) respond to stimulation of the somatostatin receptor (SSTR) by somatostatin (SST) by inhibiting the action of adenylyl cyclase, reducing the cell’s secretory and proliferative capabilities. The role of AIP in this process is unknown, but cells with defective/absent AIP (B) also have a reduction in Gai-2 and so a lack of response from SST binding to SSTR with resulting disinhibition of adenylyl cyclase and increased GH secretion and cell proliferation.