Cell surface expression levels of different N-terminal GPR83 deletion mutants compared to wild type GPR83 which was set to 100% (absorption (492/620): 0.31 ± 0.01). The Gpr83 variants were detected using an HA-ELISA system as previously reported . Untagged GPR83 served as the negative control. Data were assessed from a minimum of three independent experiments, each performed at least in triplicate, and are represented as mean + SEM. ***p ≤ 0.001 (unpaired t-test, two-tailed).