Molecular transduction mechanisms in invertebrate tase receptor.

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1. Fluctuation of the receptor current. which flows through the outer lumen of the labellar chemosenosry hair of the fleshfly, was analyzed. The fluctuation was concluded to reflect the open-shut dynamics of sugar-operated transducer ion-channels. From the difference of dynamics between sucrose and rialtose and very rapid development of the receptor current upon stimulation, the transducer channel was suggested to be complexed with the sugar receptor molecule.2. We applied patch-clamp technique to the isolated labellar taste cells, prepared from the labellum of pupa 2 - 3 days before eclosion with enzymatic treatment. Many taste cells evoked impulses spontaneously. Sucrose activated single channel current was observed from the isolated out-side patch, confirming the above conclusion.3. Taste reception mutants of Drosophila nielanogaster isolated by Dr. Tanimura were analyzed. The Trehalose-site mutant (X-chromosome) was inferred to have low affinity trehalose receptor molecule. A newly isolated pyranose-site mutant (the third chropiosome) was suggested to have less pyranose-site receptor molecules on the receptor membrane.4. A candidate of glutathione receptor molecule, R5, was isolated and purified from Hydra Japonica, making use of monoclonal antibodies and photoaffinity labelling. This molecule had the molecular weight of 200 kDa and was located on the surface of nemotocytes.5. The labellar salt receptor cell of the fleshfly had receptor sites for sugar analogues, 1,6 anhydroglucitols and for dibutylyl-cGMP, showing wide range of recepton modality in this taste cell.