Fig. 1. The CG17415 receptor responds to DH₃₁ application but requires the presence of the RCP. Cells were transfected with CG17415 and CRE-luc DNA and assayed for increases in luciferase activity as a result of peptide exposure. Values are means ± S.E.M. from six wells derived from two independent transfections, and expressed as a percentage of vehicle-treated cells. (A) In NIH 3T3 cells, 1 µmol l^–1 DH₃₁ elicited a significant difference in cAMP levels (P<0.007, two-tailed t-test; Excel) compared to vehicle controls, and did not respond to any of 29 other native and heterologous peptides. (B) Dose–response curve of DH₃₁ sensitivity in HEK cells expressing CG17415 and CG4875 (dRCP) DNA. The maximum response was twofold and the estimated EC₅₀ is 0.5 µmol l^–1. (C) Dose–response curve of DH₃₁ sensitivity in HEK cells expressing CG17415 and human RCP. Note the much larger (10-fold) difference in signal intensity, and an estimated EC₅₀ of 116 nmol l^–1.