Elementary response of olfactory receptor neurons to odorants.
Signaling by heterotrimeric GTP-binding proteins (G proteins) drives numerous cellular processes. The number of G protein molecules activated by a single membrane receptor is a determinant of signal amplification, although in most cases this parameter remains unknown. In retinal rod photoreceptors, a long-lived photoisomerized rhodopsin molecule activates many G protein molecules (transducins), yielding substantial amplification and a large elementary (single-photon) response, before rhodopsin activity is terminated. Here we report that the elementary response in olfactory transduction is extremely small. A ligand-bound odorant receptor has a low probability of activating even one G protein molecule because the odorant dwell-time is very brief. Thus, signal amplification in olfactory transduction appears fundamentally different from that of phototransduction.
Bhandawat
Vikas
V
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. vbhanda@mail.jhmi.edu
Reisert
Johannes
J
Yau
King-Wai
KW
D000098:Acetophenones / Q000378:metabolism* / Q000494:pharmacology; D000200:Action Potentials; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002469:Cell Separation; D003511:Cyclohexanols / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D000077591:Eucalyptol; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D039821:Monoterpenes / Q000378:metabolism* / Q000494:pharmacology; D009812:Odorants; D018034:Olfactory Receptor Neurons / Q000166:cytology / Q000502:physiology*; D010766:Phosphorylation; D011894:Rana pipiens; D018035:Receptors, Odorant / Q000378:metabolism*; D015398:Signal Transduction; D012903:Smell / Q000502:physiology
D000098:Acetophenones; D003511:Cyclohexanols; D008024:Ligands; D039821:Monoterpenes; D018035:Receptors, Odorant; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases; C038699:acetophenone; D000077591:Eucalyptol; D002118:Calcium