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among them pheromonal active substances from mice urine.
Therefore, TAARs were currently suggested to be a second class of
olfactory receptors (OR) in the olfactory epithelium (OE) of
vertebrates in addition to the canonical ORs. In contrast to several
deorphanized mouse TAARs, agonists for the functional human
TAAR-genes 2, 5, 6, 8 and 9 that are potentially expressed in the
human OE have not been determined so far. Moreover, the
physiological relevance of TAARs still remains elusive. We present
the first sucessful functional expression of a human TAAR and the
agonists of human TAAR5. We performed a ligand-screening using
recombinantly expressed TAARs in Xenopus laevis oocytes and
HEK293/HANA3A cells. In order to measure receptor activity, we
used 2-electrode voltage clamp technique and cAMP-dependent
reporter-gene assays. As a result, human TAAR5 can be activated
by trimethylamine (TMA) and with less potency and efficacy by
dimethylethylamine (DMEA), but not by any other of the 25 tested
single amines with related chemical structure or other odorant
mixtures. TMA is the prototype of fishy odor with a low odor
threshold. It is used for cholin metabolism and appears in human
vaginal secretion. This results demonstrate that human TAARs can
be functionally expressed in heterologues systems and human
TAAR5 responses can specifically evoked by TMA and DMEA.
#P39
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
Ectopic expression of human olfactory receptors
Caroline Flegel, Stavros Manteniotis, Sandra Ostholt,
Guenter Gisselmann, Hanns Hatt
Ruhr University Bochum/Cellphysiology Bochum, Germany
Olfactory receptors (ORs) provide the molecular foundation for the
detection of volatile odorant molecules from the environment.
Recent studies showed that the expression of these receptors is not
restricted to the olfactory epithelium (e.g. testes, prostate and gut).
The aim of this work is to create a comprehensive expression
analysis of ectopically expressed olfactory receptors in several
tissues of the human body. Isolated RNA from several human
tissues were analyzed by Next Generation Sequencing with the
Illumina Genome Analyzer II and compared to a panel of already
existing sequencing data of other different human tissues. These
data show that human tissues express a large number of ORs
which was verified by quantitative RT-PCR. We could observe the
presence of ORs which were expressed in one particular type of
tissue as well as ORs which presented a broader distribution.
Further characterization of these ORs will provide new insights
to the physiological role of distinct ORs outside the olfactory
epithelium.
#P40
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
Diffusion-based molecular dynamics of odorant binding in
olfactory receptors
Peter C. Lai, Chiquito J. Crasto
University of Alabama at Birmingham Birmingham, AL, USA
With increasing availability of high performance computing
systems, all-atom molecular dynamics (MD) simulations of
olfactory receptor (OR) models in realistic chemical and
thermodynamic environments are almost indispensable so that
insight may be gained into the molecular basis of odor-ligand OR
activation. We performed a series of MD simulations within a
solvated lipid bilayer system of the human OR, OR 17-209
(OR1G1). To further approach physiological conditions of the
chemical environment surrounding an olfactory receptor,
experimentally-determined (Matarazzo, et al. 2005) activating
concentrations of isoamyl acetate molecules were randomly
introduced into the extracellular solvent space instead of docking a
single molecule into the solvent accessible binding pocket of an
otherwise static receptor structure. This novel technique allows the
receptor to sample its own conformational space while the ligand
molecules are free to interact with it, allowing the identification of
the entry pathway into the binding pocket. In addition, systems of
varying odorant concentrations and different odorant combinations
can be simulated and compared to experimental results. Finally,
measuring structural changes in the OR as it undergoes the
transition from inactive to active conformations helps to further
elucidate the mechanism for receptor activation and odorant
specificity. References: Matarazzo, V., Clot-Faybesse, O., Marcet,
B., Guiraudie-Capraz, G., Atanasova, B., Devauchelle, G., Cerutti,
M., Eitievant, P., and Ronin, C. Chem. Senses 30, 691-701 (2005)
Acknowledgements: NIH (NIDCD) (1R21DC011068-01)
#P41
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
Ligand-Dependent Olfactory Receptor Selectivity for Olfactory
Transduction and Modulation
Yiqun Yu, Chunbo Zhang
Illinois Institute of Technology Chicago, IL, USA
In the mammalian olfactory system, one olfactory sensory neuron
(OSN) expresses a single olfactory receptor gene. We characterized
a subset of mouse OSNs (Ho-OSNs) in intact mouse olfactory
turbinates using calcium imaging. Ho-OSNs were sparsely
positioned in the most ventral olfactory receptor zone, and were
sensitive to 2-heptanone (Ho), heptaldehyde (H) and cis-4-heptenal
but not to other six odorants tested. Odor-evoked amplitudes were
dose-dependent and saturated within one logarithm unit of
concentration, a feature comparable to that from isolated OSNs.
Application of eight pharmacological reagents affecting adenylate
cyclase (AC) or phospholipase C (PLC) pathways showed that
Ho and H activated Ho-OSNs through distinct transduction
pathways. Ho-evoked responses were mediated by AC-cAMP
signaling, while H triggered the PLC-DAG-PKC pathway.
Ruthenium Red and 2-aminoethoxydiphenyl borate, reagents
inhibiting IP
3
signaling, had no effects on either Ho- or H-evoked
responses. Cross-adaptation and binary mixture studies indicate
that Ho and H competed for the same binding sites in Ho-OSNs.
Abstracts | 41
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