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.
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. vbhanda@mail.jhmi.edu
Vikas
V
Bhandawat
Johannes
J
Reisert
King-Wai
KW
Yau
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