Abstracts - Association for Chemoreception Sciences

pregnancy block. In order to understand how pheromones are
detected by the vomeronasal receptors, it is essential to know
which receptors are activated by a given chemical. However,
identifying cognate ligands for the V2Rs has been challenging,
partly because they are poorly localized to the surface of
heterologous cells. Here, we show the establishment of
heterologous cell system to functionally identify the V2Rs and
demonstrate that the ESP ligands can differentially activate the
V2Rs. We also show the large extracellular domain of the V2Rs
plays a critical role in ligand selectivity. Our results provide a
platform to characterize ligand selectivity of the V2Rs and suggest
that a unique mechanism that regulates the functional expression
of the V2Rs.
#P173 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Muscarinic Receptor M3 Potentiates the Function of a Broad
Range of Mammalian Odorant Receptors
Yun R. Li 1 , Hiroaki Matsunami 1, 2
1
Department of Molecular Genetics and Microbiology,
DurhamDepartment of Molecular Genetics and Microbiology,
Duke University Medical Center Durham, NC, USA,
2
Department of Neurobiology, Duke University Medical Center
Durham, NC, USA
Mammalian olfaction begins with the binding of odorant
molecules to specific odorant receptors (ORs), which are
expressed on the surface of olfactory sensory neurons (OSNs)
and make up the largest family of G-protein coupled receptors
(GPCRs). Here we show that type 3 muscarinic acetylcholine
receptor M3, a non-OR Class A GPCR expressed in OSNs,
enhances odorant-specific response of a large set of ORs.
Coexpression of M3 in heterologous cells produces an ~10-fold
leftward shift in EC50 values and increases the maximum response
by 25-1000% for a broad range of ORs in the cAMP-mediated
luciferase reporter gene assays for OR activity. Coexpression of
M3 does not enhance the cell-surface expression of the ORs.
Thus, the action of M3 is distinct from that of known accessory
factors, such as the RTPs. The M3-dependent potentiation of OR
activity is significantly enhanced in the presence of RTP1,
indicating that the effect of M3 is synergistic and increases the
response of ORs already at the cell surface. M3 potentiation of
OR activation is further enhanced by muscarinic agonist
carbachol, but inhibited by the muscarinic inverse agonist
atropine. Conversely, OR activation by cognate odors causes the
activation of M3 downstream signaling by eliciting a Ca 2+
response, an effect that is inhibited when cells are simultaneously
exposed to odor and atropine. The interaction and crosstalk
observed between ORs and M3 in heterologous cells is likely
dependent on the ability of these GPCRs to form stable
heterometric complexes, as ORs and M3 coprecipitate each other
in HEK293T cells. Our study suggests that OR and M3
heteromers functionally couple with one another, and will serve as
an effective screening tool to identify active ligands for the ORs.
This work was supported by NIH-NIDCD. Acknowledgements:
NIH-NIDCD Duke Undergraduate Research Support Grants
#P174 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
The OR37 subfamily: establishment of the clustered expression
pattern
Jörg Strotmann, Andrea Bader, Verena Bautze, Desirée Haid,
Heinz Breer
Institute of Physiology, University of Hohenheim Stuttgart,
Germany
In contrast to most other olfactory sensory neuron (OSN)
populations, cells expressing a member from OR37 subfamily of
odorant receptor (OR) genes are restricted to a small central patch
of the mouse olfactory epithelium (OE). To obtain insight into the
regulatory mechanisms which determine this unique spatial
organization, a lineage tracing approach (mOR37C-IRES-Cre)
was performed to visualize all cells that transcribed OR37C at any
time during differentiation. As expected, labelled OSNs were
found in the typical central patch; surprisingly, however,
numerous additional OSNs were found which were broadly
dispersed throughout the OE. Using in situ hybridization, the
mRNA for OR37C could only be detected in those cells located
in the typical patch, suggesting that all ectopic OSNs had ceased
OR37C expression. The question whether these cells may
undergo premature apoptosis was addressed by analysis for active
caspase-3; none of them, however, expressed this pro-apoptotic
marker. A close examination of the ectopically positioned OSNs
revealed that they all extended an axon towards the olfactory bulb
(OB), and indeed many glomeruli could be detected which
contained a few labelled fibers. The location of these glomeruli in
the medial and lateral domains of the bulb indicated that these
represented glomeruli that receive input from OSN populations
expressing other ORs than OR37C. Altogether, these data
indicate that OSNs which initially express OR37C outside the
typical patch do not continue, but switch to the expression of a
different OR gene, suggesting the involvement of a mechanism
downstream of gene choice that restricts OR37C expression to
the central patch. Acknowledgements: Supported by the Deutsche
Forschungsgemeinschaft
#P175 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Expression of odorant receptor genes on the olfactory
epithelium following olfactory nerve transection
Yongxiang Wei 1 , Yuehong Liu 2 , Ling Yang 2 , Xutao Miao 3 ,
Yayan Lu 2 , Xiaochao Liu 2
1
Beijing Chaoyang Hospital,Capital Medical University Beijing ,
China, 2 Beijing Tongren Hospital,Capital Medical University
Beijing, China, 3 Beijing Jishuitan Hospital Beijing, China
Objective To construct unilateral olfactory nerve transection
model of rats and observe the change of expression quantity and
position of odorant receptors in regenerated olfactory epthelium.
Methods Experimental group and control group consisted of 20
and 12 rats respectively. The left olfactory bulb of the rats in the
former group was exposed under microscope and the olfactory
nerve was transected along cribriform plate; the rats in control
group didn’t accept any treatment. The change of cell
morphology, and quantity and thickness of epithelium were
observed by HE staining. The expression pattern of olfactory
receptor genes Olr287, Olr226, Olr1493 and Olr1654 in olfactory
epithelium and the distribution and quantity changes of each gene
P O S T E R S
Abstracts are printed as submitted by the author(s)
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