2009 Abstracts - Association for Chemoreception Sciences

#P163 Poster session IV: Chemosensory transductionand perireceptor eventsPI3K mediated signaling in lobster olfactory signaltransductionElizabeth A Corey 1 , Adeline Pezier 1 , Katharina Klasen 1 ,Barry W Ache 1,21Whitney Lab University of Florida St Augustine, FL, USA,2Center for Smell and Taste, and McKnight Brain Institute Depts.of Zoology and Neuroscience, University of Florida Gainesville,FL, USAOdors are identified by the brain through a distributed processthat begins with the primary olfactory receptor neurons(ORNs). In organisms in which odorant molecules bind toG protein-coupled receptors (GPCRs) on the ORNs to initiatesignal transduction, involvement of phosphoinositide 3-kinase(PI3K) activity in olfactory signal transduction would suggesta potential role for the GPCR-activated class I PI3K b and gisoforms. Using isoform-specific antibodies, we identified aprotein in the olfactory signal transduction compartment oflobster ORNs that is immunoreactive with an antibodydirected against mammalian PI3Kg. The lobster PI3K coimmunoprecipitateswith the a and bg G protein subunits, andan odorant-evoked increase in phosphatidylinositol (3,4,5)-trisphosphate, the product of PI3K activity, can be detected inmembranes prepared from the signal transduction compartmentof the ORNs. The isoform-specific PI3Kg inhibitorAS-252424 reduces the odor-evoked output of lobster ORNsin vivo. Additionally, the catalytic subunits of PI3Kb and g, aswell as odorant-dependent PI3K activity, can be detected in aciliary membrane preparation from rat ORNs. Collectively,these findings support a potential role for PI3K-dependentphospholipid signaling in olfactory transduction and suggestthat PI3K-mediated signaling in olfactory signal transductionmay be conserved across species.#P164 Poster session IV: Chemosensory transductionand perireceptor eventsDifferent response properties between Type II andType III taste bud cells in mouse fungiform papillaeRyusuke Yoshida 1 , Toshiaki Yasuo 1 , Yoshihiro Murata 1 , MasashiJyotaki 1 , Yuchio Yanagawa 2 , Kunihiko Obata 3 , Hiroshi Ueno 4 ,Robert F. Margolskee 5 , Yuzo Ninomiya 11Sect. of Oral Neurosci., Grad. Sch. of Dental Sci., Kyushu Univ.Fukuoka, Japan, 2 Grad Sch. of Med., Gumma Univ. Maebashi,Japan, 3 RIKEN Wako, Japan, 4 Nara Women’s Univ. Nara, Japan,5Mount Sinai Sch. of Med. NY, NY, USATaste bud cells are classified into 4 groups (Type I ~ IV) accordingto their morphological and functional characteristics. Amongthem, Type II cells express sweet, bitter and umami taste receptorsand transduction components, suggesting that Type II cells maybe responsible for these taste qualities. Type III cells possessputative sour taste receptors, suggesting that these cells may besour taste receptor cells. To clarify taste response properties ofType II and III cells, we investigated taste responses of individualmouse fungiform taste bud cells expressing gustducin (Type II) orGAD67 (Type III). We recorded taste responses from gustducin-GFP and GAD67-GFP taste bud cells, or examined theexpression of gustducin and GAD67 by the single cell RT-PCRafter recording of taste responses. Both Type II and III cellsgenerated action potentials in response to taste stimuli, suggestingthat these cells may transmit taste information to gustatory nervefibers. Type II cells responded best to sweet, bitter, or umamistimuli whereas Type III cells responded to sour stimuli andelectrolytes. These results are well consistent with those ofprevious molecular studies and suggest that Type II and Type IIIcells may contribute to detection and perception of different tastequalities. Supported by KAKENHI 18077004, 18109013 (YN)and 19791367 (RY).#P165 Poster session IV: Chemosensory transductionand perireceptor eventsReceptor-dependent PIP 2 resynthesis restores sweet andbitter inhibitions of potassium currentsFang-li Zhao, Scott HernessThe Ohio State University Columbus, OH, USAPhosphatidylinositol 4,5-bisphosphate (PIP 2 ), a lipid signalingagent, is a recognized component of sweet, bitter, and umamitransduction cascades. It is also a well known activator of ionchannels in other cellular systems. We previously established PIP 2resynthesis as important in restoring activity to outward (K V ) andinward (K IR ) potassium currents in rat posterior taste receptorcells (TRCs) after caffeine-inhibition. Here we providecorroborative evidence that suggests PIP 2 resynthesis generalizesin adaption to bitter and sweet stimuli. Kv currents, recordedfrom rat posterior TRCs with standard patch clamp techniques,were inhibited approximately 35% by m-3M3FBS, a broadspectrum PLC activator that acts to globally deplete PIP 2whether applied intracellularly (100 µM, n=32) or extracellularly(5 µM, n=57). o-3M3FMS (100 M, intracellular), an inactiveenantiomer, was without effect. Unexpectedly, depletion of PIP 2strongly influenced response profiles to cycloheximide (100 M;n=61), caffeine (20 mM; n=44), and SC45647 (100 M;n=56). After m-3M3FBS treatment, these tastants, known toinhibit K V , now actually enhanced K V . We hypothesize that thiseffect is due to PIP 2 resynthesis. To test this notion, polylysine, aPIP 2 scavenger, was added to the pipette solution and effectivelyreduced the enhancement caused by bitter (n=22) or sweet (n=19)stimulation. In addition, exogenous PIP 2 itself (10 M, n=33, 50M, n=27) did not enhance K V although 50 M PIP 2 was able toreduce K V inhibition when combined with 5 M m-3M3FBS(n=20). Collectively, these data support the notion that potassiumchannels are subject to dynamic regulation by PIP 2 and that itsresynthesis requires a signal, likely receptor-mediated, for itsinitiation.#P166 Poster session IV: Chemosensory transductionand perireceptor eventsNative TRPM5 currents recorded from posterior rat tastereceptor cellsFangli Zhao, Luc Jaber, Randy Hivley, Scott HernessThe Ohio State University Columbus, OH, USAThe ion channel TRPM5 is expressed in a subset of taste receptorcells (TRCs) and is thought essential for bitter, sweet, and umamitransduction cascades. It is permeable to monovalent cations andgated by intracellular calcium. This channel has mostly beencharacterized in heterologously expressed cells, where it is not78 | AChemS Abstracts 2009