The long-term objective of this proposal is to understand in quantitative detail the transduction mechanism in vertebrate olfactory receptor neurons (ORNs). During the current grant period, we have been able to resolve the response triggered by a single odorant-binding event on an ORN (the so- called "unitary response"). Surprisingly, we found that randomly encountered ORNs (and therefore randomly encountered odorant receptors, or ORs) all gave unitary responses of similar amplitudes, suggesting that an odorant-binding event has a very low probability of signaling downstream. In other words, the unitary response appears to reflect the effect of a single activated Golf/adenylyl cyclase complex. This phenomenon is apparently due to a very short odorant dwell-time on the OR molecule (i.e., rapid dissociation of the odorant from the OR). This short odorant dwell-time likewise dominates the termination of olfactory transduction. Hence, the traditionally believed determinants for terminating G-protein-coupled receptor (GPCR) signaling, namely, receptor phosphorylation and subsequent arrestin binding, are unimportant at least at the level of the unitary response, although they may still be important with intense and prolonged odorant stimulation. So far, the above results have been obtained from amphibian ORNs and in low-Ca2+ solution (in order to boost the unitary-response amplitude). In this application, we propose to continue experiments with amphibian ORNs but at the same time to use also mouse ORNs, which offer the distinct advantage of genetic manipulations.
Aim 1 is to obtain the best estimate of the olfactory unitary-response amplitude in frog ORNs in physiological conditions (i.e., normal external Ca2+), to characterize its spatial spread along the olfactory cilium, to dissect its membrane-current components (cyclic-nucleotide-gated current versus Cl current), and to estimate the number of unitary responses required for bringing the ORN to firing threshold.
Aim 2 is to launch a similar detailed study of the unitary response in mouse ORNs, which will serve as the groundwork for examining available genetic mouse lines for olfactory transduction.
Aim 3 is to study/dissect Ca-dependent and Ca-independent adaptation by ORNs in more detail, largely by making use of genetic mouse lines.
Aim 4 is to study constitutive OR activity in the absence of odorants, which so far has received little attention in vertebrate olfactory transduction. We have noticed this phenomenon in the course of previous experimentation. The experimental approach will involve predominantly suction-pipette recording from single ORNs of frog and WT or genetically engineered mice.

Public Health Relevance

The studies proposed in this application will enhance our understanding of olfactory transduction in vertebrate olfactory receptor neurons in the nose. Any new information derived from these studies will also be highly relevant to disease states affecting odorant detection by the nose.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC006904-09
Application #
8277371
Study Section
Somatosensory and Chemosensory Systems Study Section (SCS)
Program Officer
Sullivan, Susan L
Project Start
2004-08-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
9
Fiscal Year
2012
Total Cost
$333,975
Indirect Cost
$130,332
Name
Johns Hopkins University
Department
Neurosciences
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Ben-Chaim, Yair; Cheng, Melody M; Yau, King-Wai (2011) Unitary response of mouse olfactory receptor neurons. Proc Natl Acad Sci U S A 108:822-7
Bhandawat, Vikas; Reisert, Johannes; Yau, King-Wai (2010) Signaling by olfactory receptor neurons near threshold. Proc Natl Acad Sci U S A 107:18682-7
Yau, King-Wai; Hardie, Roger C (2009) Phototransduction motifs and variations. Cell 139:246-64
Zhao, Yun; Lee, Andy H; Yau, Kelvin K W et al. (2009) A score test for assessing the cured proportion in the long-term survivor mixture model. Stat Med 28:3454-66
Do, Michael Tri H; Kang, Shin H; Xue, Tian et al. (2009) Photon capture and signalling by melanopsin retinal ganglion cells. Nature 457:281-7
Cheng, Ning; Tsunenari, Takashi; Yau, King-Wai (2009) Intrinsic light response of retinal horizontal cells of teleosts. Nature 460:899-903
Fu, Yingbin; Kefalov, Vladimir; Luo, Dong-Gen et al. (2008) Quantal noise from human red cone pigment. Nat Neurosci 11:565-71
Luo, Dong-Gen; Xue, Tian; Yau, King-Wai (2008) How vision begins: an odyssey. Proc Natl Acad Sci U S A 105:9855-62
Guler, Ali D; Ecker, Jennifer L; Lall, Gurprit S et al. (2008) Melanopsin cells are the principal conduits for rod-cone input to non-image-forming vision. Nature 453:102-5
Reisert, Johannes; Yau, King-Wai; Margolis, Frank L (2007) Olfactory marker protein modulates the cAMP kinetics of the odour-induced response in cilia of mouse olfactory receptor neurons. J Physiol 585:731-40

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