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Principal Investigator: KING-WAI YAU
Organization: JOHNS HOPKINS UNIVERSITY
Fiscal Year: 2024
Award: $409,375
Funding agency: National Institute on Deafness and Other Communication Disorders
The long-term objective of this proposal is to understand in quantitative detail the cAMP- and Ca2+-signalings in sensory transduction by olfactory receptor neurons (ORNs). We shall focus on the canonical
olfactory-transduction mechanism in the vertebrate main olfactory epithelium. This mechanism involves a
cAMP-signaling cascade, leading to Na+ and Ca2+ influxes through a cyclic-nucleotide-gated (CNG), non-selective cation channel to depolarize the ORN to firing threshold. The Ca2+ influx leads to signal amplification
via an inward Ca2+-activated Cl current, as well as olfactory adaptation via multiple Ca2+-activated negative-feedback pathways. Recently, however, the significance and performance of the negative-feedback pathways
are thrown into doubt and confusion. In Aim 1, we propose to re-examine this question and to settle it once
and for all.
Most recently, by using M71-monoclonal-nose mouse ORNs, we have succeeded in quantifying the
density of M71-OR molecules on the olfactory cilia membrane. We also found that an M71-OR, when liganded
with acetophenone (among the most efficacious odorants for M71-OR), nonetheless still has a very low
probability of success (nominally ~10-4) in activating a single downstream Golf/adenylyl cyclase III effector
complex. This low probability is very different from the situation in rod phototransduction, about which we
recently showed that one photoexcited rhodopsin activates 10-20 rod transducin/cGMP-phosphodiesterase
effectors. Thus, a ligand-activated GPCR pathway may be quite different in signal amplification from a light-activated GPCR pathway. In Aims 2, we propose to study another mouse nasal chemoreceptor, TAAR4, which
is exceedingly sensitive to 2-phenylethylamine, a predator odorant aversive to mouse. The objective is to
compare the findings with those from M71-OR, to figure out whether TAAR4's molecular density on the cilia's
surface membrane is very different from that of M71-OR, and to ask whether the amplification at the
downstream G-protein/effector enzyme complex activation step is any different from the case of M71-OR. In
Aim 3, as another comparison, we shall address the same questions for mOR256-17, an OR with one of the
highest abundances known so far in the main olfactory epithelium and with an unusually broad odorant
spectrum.
Quantitatively elucidating the steps of olfactory transduction will provide great insight into normal
olfactory functions, as well as malfunctions arising from genetic defects in the transduction pathway, as amply
demonstrated by the huge success as such in the case of visual transduction.
Terms: <3'5'-cyclic ester of AMP><3,5 cyclic AMP synthetase><Acetophenones><Address><Adenosine Cyclic 3',5'-Monophosphate><Adenosine Cyclic Monophosphate><Adenosine, cyclic 3',5'-(hydrogen phosphate)><Adenyl Cyclase><Adenylate Cyclase><Adenylyl Cyclase><Binding><Biochemical><Cations><Cell Communication and Signaling><Cell Signaling><Cellular biology><Chemoreceptors><Cilia><Complex><Cone Photoreceptors><Confusion><Confusional State><Cyclic AMP><Cyclic GMP><Cyclic Nucleotides><DNA Molecular Biology><Feedback><G Protein-Complex Receptor><G Protein-Coupled Receptor Genes><G Protein-Coupled Receptor Signaling><G-Protein-Coupled Receptors><G-Proteins><GPCR><GPCR Signaling><GTP-Binding Proteins><GTP-Regulatory Proteins><Genetic Alteration><Genetic Change><Genetic defect><Golf><Guanine Nucleotide Coupling Protein><Guanine Nucleotide Regulatory Proteins><Guanosine Cyclic Monophosphate><Hand><Inhibitory Gt G-Protein><Intracellular Communication and Signaling><Laboratories><Ligands><Light><Light Signal Transduction><Math Models><Mechanical Aspiration><Mediating><Membrane><Mental Confusion><Mice><Mice Mammals><Molecular><Molecular Biology><Molecular Interaction><Multienzyme Complexes><Murine><Mus><Mutation><Nasal><Nasal Passages Nose><Nose><Odor Receptor Protein><Odorant Receptor Proteins><Odorant Receptors><Olfactory Epithelium><Olfactory Receptor Neurons><Olfactory Receptor Proteins><Pathway interactions><Performance><Phenethylamines><Phenylethylamines><Phosphodiesterases><Photoradiation><Phototransduction><Probability><Receptor Protein><Respiratory System, Nose, Nasal Passages><Retinal Cone><Rhodopsin><Rod><Rod Photoreceptors><Sensory><Signal Transduction><Signal Transduction Systems><Signaling><Suction><Suction Drainage><Surface><Transducin><Uncertainty><Visual Purple><Visual Transduction><Work><adenosine 3'5' monophosphate><adenylyl cyclase III><adenylyl cyclase type III><biological signal transduction><cAMP><cGMP><cell biology><cone cell><density><doubt><enzyme complex><examination questions><experiment><experimental research><experimental study><experiments><gene manipulation><genetic manipulation><genetically manipulate><genetically perturb><genome mutation><hands><insight><mathematic model><mathematical model><mathematical modeling><membrane structure><pathway><phosphoric diester hydrolase><receptor><retinal rods><rod cell><success>