Different N-terminal GPR83 deletion mutants were functionally characterized and compared with the wild type GPR83 (A/B) or an empty vector control (pcDps, B/C/D). Shown are Gq/11-activation in A), MAPK-activation in B), G12/13-activation in C) and Gs/Gi-signaling properties in D). Wild type GPR83 serves as a positive control for Gq/11-signaling (A). The TSH-stimulated TSHR serves as a positive control for MAPK- and G12/13-signaling (B/C). Forskolin-stimulation shows Gs-activity of the used cell line by activating adenylyl cyclase. A decreased value of forskolin-stimulation in comparison to the empty vector control would indicate inhibitory Gi-activity. Data were evaluated from a minimum of three independent experiments, each performed at least in triplicate. Data were calculated as fold over the empty vector control, set to 1 (A: 4828.67 ± 1165.71, B: 1334800 ± 326986.69, C: 2095559.89 ± 447919.48 relative light units; D: 2.03 ± 0.15 nM cAMP). Data represent mean + SEM. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 (unpaired t-test, two-tailed).