Page 229 - Veterinary Immunology, 10th Edition
P. 229
such as adenylate cyclase, phospholipase C, and some protein
VetBooks.ir kinases.
FIG. 8.6 GTP-binding proteins (G-proteins) can act as signaling
switches to turn cell functions on and off. They are often activated in
the initial stages of signal transduction.
When activated by a G-protein, phospholipase C splits the
membrane-bound lipid, phosphatidylinositol 4,5-bisphosphate
(PIP ), into two messenger molecules, inositol trisphosphate and
2
diacylglycerol (Fig. 8.7). Inositol trisphosphate binds to intracellular
2+
receptors releasing Ca from internal stores and increases the
2+
concentration of intracellular Ca . These calcium ions can activate
many proteins. The diacylglycerol remains in the plasma membrane
229
