ORIGINAL ARTICLE Functional

screening system for yeast-secreted peptides acting on G-protein coupled receptors Tomohiro Shigemori, Kouichi Kuroda and Mitsuyoshi Ueda* We established a novel functional screening system for peptides acting on G-protein coupled receptors (GPCRs). Pep-tides are a promising drug scaffold because of their intermediate molecular size between that of therapeutic small molecules and antibodies. They also offer potential advantages of targeting not only membrane proteins but also intracellular protein–protein interactions. Phage display technology has been used for exploring novel peptides act-ing on GPCRs, but it is unclear whether the identified peptides functionally modulate targets because the technol-ogy selects peptides based on binding ability but not functional activity to targets. In a novel screening system that we established, yeast cells were utilized as a peptide producer while mammalian cells stably producing the receptor for glucagon-like peptide 1 (GLP1R) were used as a biosensor for receptor activation. Three kinds of GLP1R agonists secreted by yeasts were successfully detected for their functional activities without any purification and condensa-tion of those peptides. By applying the functional screening system, we were able to identify GLP1R agonist-secreting yeasts based on GLP1R activation from the cell mixture containing a number of background yeasts that produced non-active control peptides. Further applications of this system would include not only activity evaluation of bioactive peptides without chemical synthesis but also discovery of novel peptides activating druggable GPCRs