Figure 1.

A modified C terminus C5a peptide, C5a^pep, is a full agonist for Gα_i coupling. A, schematic representation of C5a binding to C5aR1. There are two sites of interaction, one involving the N terminus of C5aR1 and the other involving the extracellular loops. B, the primary sequence and modification of C5a^pep, which is derived based on the C terminus of C5a. C, C5a^pep behaves as a full-agonist in GloSensor-based cAMP assay. HEK-293 cells expressing C5aR1 were transfected with F22 plasmids. 24 h post-transfection, the cells were stimulated with indicated concentrations of C5a and C5a^pep followed by recording of bioluminescence readout. D, Gα_i coupling induced by C5a and C5a^pep measured in CHO cells using LANCE cAMP assay. CHO cells stably expressing C5aR1 were stimulated with the indicated concentrations of respective ligands. The data presented in C and D represent the means ± S.E. of three to five independent experiments, and the EC₅₀ values of C5a and C5a^pep were analyzed using unpaired t test. ***, p < 0.001.