Phosphoinositide second messengers in olfaction.
Olfactory stimuli (odorants) are detected and recognized by binding to receptors belonging to the G-protein-coupled receptor superfamily. The binding of odorants to some receptors stimulates the activity of an odorant-sensitive phospholipase C (PLC) thereby generating the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 plays a key role in membrane depolarization by binding to a receptor that is itself a cation channel. The formation of DAG is expected to stimulate the activity of protein kinase C (PKC). PKC, together with G-protein-coupled receptor kinases, mediates signal termination by phosphorylation of odorant receptors and possibly other substrates. This review summarizes recent evidence regarding the role of phosphoinositide-derived second messengers in the molecular events underlying olfactory signaling. In addition, the role of calcium as a "third messenger" that provides a mechanism for interaction between phosphoinositide second messengers and components of the cyclic AMP signaling pathway is also discussed.
Bruch
R C
RC
Department of Zoology and Physiology, Louisiana State University, Baton Rouge 70803, USA.
D000818:Animals; D000242:Cyclic AMP / Q000502:physiology; D004075:Diglycerides / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D009812:Odorants; D010716:Phosphatidylinositols / Q000502:physiology*; D015290:Second Messenger Systems; D015398:Signal Transduction; D012903:Smell; D010738:Type C Phospholipases / Q000378:metabolism
D004075:Diglycerides; D010716:Phosphatidylinositols; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins