1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

345 Poster Chemosensory Molecular Genetics andVNO/PheromonePOTENTIATION AND INHIBITION AMONG ODORANTSACTING ON HUMAN VN1-TYPE RECEPTORSShirokova E. 1 , Krautwurst D. 1 1 German Institute of Human NutritionPotsdam-Rehbruecke, Nuthetal, GermanyThe human nose is exposed to odours that are shaped in many casesrather by mixtures of odorants than by a single odorant. For example,the key aroma compounds from food or human skin emanations arequite diverse, but also include homologous series of aliphatic odorants,that vary over size and functional groups. When tested with individuallyapplied odorants, olfactory receptors (ORs) display specific odorantrecognition profiles. At the receptor level, related odorants canantagonize each other´s effect. The complex actions of odorant mixtureson OR, however, are poorly understood. In 96well Ca 2+ imaging FLIPRexperiments, we identified specific C7-C11 aliphatics as best agonistsfor all five human VN1-type receptors (VN1Rs), when expressed inHeLa/Olf cells. In binary mixtures with agonists, related odorants withthe same functional group, but with a carbon chain length C11acted as antagonists. Related odorants with a different functional groupbut similar length had no effect by themselves, but potentiated the effectof the agonist. For example, VN1R1 responded specifically toaldehydes with decanal as best agonist. Hexanal and undecanalconcentration-dependently inhibited the decanal responses, whiledecanol had no effect by itself, but potentiated the decanal responseabout 2-fold. Similar effects were observed with the other VN1Rs.Antagonism and potentiating effects may thus account for thedominating or masking of odorants in complex mixtures. Ourobservations with binary mixtures anticipate an even higher level ofcomplexity of odorant coding at the level of ORs in nose.346 Poster Chemosensory Molecular Genetics andVNO/PheromoneIDENTIFICATION OF A MOUSE V2R RECEPTOREXPRESSED IN VOMERONASAL SENSORY NEURONSSTIMULATED BY A MALE-SPECIFIC PEPTIDE ESP1Haga S. 1 , Kimoto H. 1 , Yanagawa T. 1 , Sato K. 1 , Touhara K. 1 1 TheUniversity of Tokyo, Chiba, JapanThe vomeronasal organ (VNO) is thought to be responsible formediating pheromone information in mice. We recently identified asex-specific peptide, named ESP1, in tears of male mice. The secretedESP1 appears to be transferred to the female VNO wherein it elicits anelectrical response in vomeronasal sensory neurons (VSNs), andtherefore, ESP1 is a candidate sex-pheromone in mice. The ESP1 genewas a member of a novel multigene family (ESP family) that composedof ~30 homologous genes in mouse genome. Some of orthologousgenes were found in rat genome, albeit the number was smaller thanthat in mice, whereas no apparent ESP gene was found in humangenome, suggesting that the ESP family has rapidly evolved during theevolutional process. ESP1 induced c-Fos expression in V2R-expressingVSNs that were stained with a V2Rp probe potentially hybridizing witheight homologous V2Rs. To identify which V2R in the V2Rpsubfamily is expressed in c-Fos-induced VSNs, we designed a set ofprobes from different regions of V2Rp and performed high-stringencyin situ hybridization. One probe that hybridized with only a V2Rp5gene product recognized 100% of c-Fos-positive VSNs. These resultssuggest that a ligand spectrum of a pheromone receptor is narrowlytuned and specific, not like in main olfactory system wherein eachodorant is recognized by a different set of olfactory receptors. [supported by PROBRAIN, Japan ]347 Poster Chemosensory Molecular Genetics andVNO/PheromoneAN EARLIER ORIGIN FOR THE VOMERONASAL SYSTEM:TRP2 IN SEA LAMPREY (PETROMYZON MARINUS)Grus W.E. 1 , Zhang J.G. 1 1 Ecology & Evolutionary Biology, Universityof Michigan, Ann Arbor, MIThe vomeronasal system (VNS) is one of two nasal chemosensorysystems found in tetrapods. Currently, the VNS is defined by twomorphological components, the vomeronasal organ and the accessoryolfactory bulb. These components are only found in tetrapods(amphibians, reptiles, and mammals). Alternatively, the VNS could bedefined by system-specific genetic components. Compared with apurely morphological view, this view gives a different picture of VNSevolution. In mammals, VNS-specific genetic components have beenwell characterized, and all three mammalian VNS-specific genes(V1Rs, V2Rs, and Trp2) have been identified in teleost fish with tissuespecificexpression, indicating that they are involved in chemosensorydetection. Additionally, studies revealed that these teleost genes are coexpressedand function together. Thus, the VNS-specific signaltransduction pathway predates the morphologically defined VNS. Here,we suggest an even earlier origin of the VNS by describing the partialsequence of Trp2, in a jawless vertebrate, the sea lamprey (Petromyzonmarinus). Expression studies could confirm that this VNS-specific genein lampreys indicates that the VNS was present in the common ancestorof jawless fish and jawed vertebrates at least 550-650 million years ago.WEG is supported by the Rackham Graduate School, the University ofMichigan Dept of Ecology and Evolutionary Biology, and NIH TrainingGrant T32 HG00040.348 Poster Chemosensory Molecular Genetics andVNO/PheromoneTWO FAMILIES OF CANDIDATE TASTE RECEPTORS INFISHESIshimaru Y. 1 , Okada S. 1 , Naito H. 1 , Nagai T. 1 , Yasuoka A. 2 , MatsumotoI. 1 , Abe K. 1 1 Applied Biological Chemistry, The University of Tokyo,Tokyo, Japan; 2 National Institute of Environmental Health Sciences,Research Triangle Park, NCVertebrates receive tastants, such as sugars, amino acids, andnucleotides, via taste bud cells in epithelial tissues. In mammals, twofamilies of G protein-coupled receptors for tastants are expressed intaste bud cells—T1Rs for sweet tastants and umami tastants (L-aminoacids) and T2Rs for bitter tastants. Here, we report two families ofcandidate taste receptors in fish species, fish T1Rs and T2Rs, whichshow significant identity to mammalian T1Rs and T2Rs, respectively.Fish T1Rs consist of three types: fish T1R1 and T1R3 that show thehighest degrees of identity to mammalian T1R1 and T1R3, respectively,and fish T1R2 that shows almost equivalent identity to both mammalianT1R1 and T1R2. Unlike mammalian T1R2, fish T1R2 consists of twoor three members in each species. We also identified two fish T2Rs thatshow low degrees of identity to mammalian T2Rs. In situ hybridizationexperiments revealed that fish T1R and T2R genes were expressedspecifically in taste bud cells, but not in olfactory receptor cells. FishT1R1 and T1R2 genes were expressed in different subsets of taste budcells, and fish T1R3 gene was co-expressed with either fish T1R1 orT1R2 gene as in the case of mammals. There were also a significantnumber of cells expressing fish T1R2 genes only. Fish T2R genes wereexpressed in different cells from those expressing fish T1R genes.These results suggest that vertebrates commonly have two kinds of tastesignaling pathways that are defined by the types of taste receptorsexpressed in taste receptor cells. Ishimaru Y. et al. Mech. Dev. 122:1310-1321 (2005)87