Abstracts - Association for Chemoreception Sciences

#P166 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Enzymatic conversion of odorants in nasal mucus affects
olfactory glomerular activation patterns and odor perception
Ayumi Nagashima, Kazushige Touhara
The University of Tokyo Tokyo, Japan
Odor information is decoded as a combination of olfactory
receptors, and thus transformed into discrete spatial patterns of
olfactory glomerular activity, which reflect differences in the
quality of odorants. We previously found that there were
differences between the ligand specificity of an olfactory receptor
in vitro and of its corresponding glomerulus in vivo for some
odorants. These observations led us to hypothesize that there
existed pre-receptor events that affected the local concentration of
a given odorant in the nasal mucus, which causes the apparent
specificity differences. Here we show that odorants with
functional groups such as aldehyde and ester are targets of
metabolic enzymes secreted in the mucus, resulting in the
conversion to corresponding acid and alcohol. Using in vivo
imaging, comparison between the activation patterns in the
olfactory bulb in the presence or absence of an enzyme inhibitor
in the mucus suggested that the spatial glomerular activity pattern
elicited by an enzyme-targeted odorant, acetyl isoeugenol, for
example, was not purely the representation of the receptor code
for acetyl isoeugenol but for the mixture of acetyl isoeugenol and
the enzymatically converted odorant, isoeugenol. Importantly,
olfactory discrimination tests revealed that the mice behaviorally
trained to associate acetyl isoeugenol to sugar rewards could not
discriminate acetyl isoeugenol after the treatment with the
enzyme inhibitor, suggesting that they perceive acetyl isoeugenol
as a different odor from the odor of acetyl isogenol during
training. These results reveal that the enzymatic conversion of
odorants in the nasal mucus appear to affect the odor quality at
the level of perception, shedding light on a unappreciated role of
nasal mucosal enzymes in odor sensation.
#P167 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
PI3K-dependent Inhibitory Signaling in Mammalian Olfactory
Receptor Neurons
Kirill Ukhanov 1 , Daniela Brunert 1 , Barry W. Ache 1,2
1
Whitney Laboratory, Center for Smell and Taste, and McKnight
Brain Institute Gainesville, FL, USA, 2 Depts. of Biology and
Neuroscience Gainesville, FL, USA
with lilial-dependent inhibition of the response to bourgeonal,
suggesting the finding can generalize to other odorant pairs.
Collectively, our findings raise the interesting specter that either
PI3K constitutively modulates OR binding, or ligand-directed
binding to the OR targets both cyclic nucleotide and
phosphoinositide signaling in mammalian ORNs.
Acknowledgements: NIH NIDCD DC001655, DC005995
#P168 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Functional implication of PI3K beta and gamma in
rodent olfaction
Daniela Brunert 1 , Katharina Klasen 1 , Elizabeth A. Corey 1 ,
Kirill Ukhanov 1 , Barry W. Ache 1,2
1
Whitney Laboratory, Center for Smell and Taste and McKnight
Brain Institute, University of Florida Gainesville, FL, USA,
2
Depts. of Biology and Neuroscience, University of Florida
Gainesville, FL, USA
Phosphatidylinositol 3-kinase (PI3K)-dependent signaling couples
to receptors for many different ligands in diverse cellular systems,
including rat olfactory receptor neurons (ORNs). Here, we
generalize the latter finding to mice by showing PI3K-dependent
inhibition of the calcium response of mouse ORNs to odorant
stimulation as well as odorant-dependent increase in
phosphoinositides in the mouse olfactory epithelium (OE)
measured in ELISA. Like rat ORNs, mouse ORNs express two
known GPCR -activated isoforms of PI3K, PI3Kb and PI3Kg.
Both isoforms are expressed in many, if not most ORNs. Isoform
specific blockers, TGX-221 (PI3Kb) and AS252424 (PI3Kg), are
equally effective in reducing both the odorant dependent rise in
phosphoinositides as well as the PI3K-dependent inhibition of the
calcium response to odorants. ORNs from transgenic mice
deficient for PI3Kg show a residual response to pan-specific PI3K
blockers, suggesting that PI3Kg plays a role but is not exclusively
responsible for PI3K mediated signaling in murine
ORNs. Collectively, our results suggest that PI3Kb and g may
have redundant function in rodent ORNs, as known to occur in
bone marrow-derived macrophages and blood platelets. Further
studies using mice deficient for PI3Kb alone and double deficient
mutants are targeted to help resolve the relative roles of the two
isoforms of PI3K in rodent olfaction. Acknowledgements:
Supported by the National Institute on Deafness and Other
Communication Disorders (DC001655, DC005995) and a Feodor
Lynen Research Fellowship from the Alexander von Humboldt
Foundation
P O S T E R S
Phosphoinositide-3-kinase (PI3K)-dependent signaling can
modulate the response of mammalian olfactory receptor neurons
(ORNs) to complex odorants. We now extend this observation to
single odorant pairs. Citral inhibited the response to octanol in 13
of 91 octanol-responsive acutely dissociated rat ORNs measured
with calcium imaging. Citral itself was not an effective ligand for
these ORNs while inhibiting the response to octanol in a
concentration-dependent manner. Blocking PI3K relieved the
citral-dependent inhibition but had no effect on the response to
octanol. Citral also inhibited in a PI3K- and concentrationdependent
manner the response to IBMX/Forskolin (IF) in about
1% of IF-responsive ORNs. We argue that citral affects PI3Kdependent
signaling being otherwise weak agonist in these ORNs.
The PI3K-dependent enhanced response to citral was blocked by
MDL12330A and SQ22536, implicating cyclic nucleotidedependent
signaling in the output. Similar results were obtained
#P169 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Regulation Of Sodium Calcium Exchanger (Ncx) Activity
By Calmodulin Or Omp In The Olfactory Signaling
Transduction Cascade
Manoj Tyagi, Frank L Margolis
Anatomy and Neurobiology, University of Maryland Baltimore
Baltimore, MD, USA
Dynamic changes in the concentrations of Na + and Ca 2+
modulate signaling in the olfactory sensory neuron (OSN).
Na/Ca exchanger (NCX) activity plays an important role in
this process and its activity is modulated by different proteins.
We reported reduced efficiency of Ca2+ extrusion by NCX in
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