The C-terminal of the α1b-adreneroceptor is a key determinant for its structure integrity and biological functions

Abstract

The C-terminal of G protein-coupled receptors is now recognized as being important for G protein activation and signaling function. To detect the role of C-terminal tail in receptor activation, we used the α1b-AR, which has a long C-terminal of 164 amino acids. We constructed the intramolecular FRET sensors, in which the C-terminal was truncated to 10 (ΔC-10), 20 (ΔC-20), 30 (ΔC-30), 50 (ΔC-50), 70 (ΔC-70), or 90 (ΔC-90). The truncated mutants of ΔC-10, ΔC-20, or ΔC-30 cannot induce FRET signal changes and downstream ERK1/2 phosphorylation. However, the truncated mutants of ΔC-50, ΔC-70, or ΔC-90 induce significant FRET signal changes and downstream ERK1/2 phosphorylation, especially ΔC-90. This is particularly true in the case of the ΔC-90, ΔC-70, or ΔC-50 which retained the potential phosphorylation sites (Ser401, Ser404, Ser408, or Ser410). The ΔC-90 showed an increase in agonist-induced FRET signal changes and ERK1/2 phosphorylation in PKC- or endocytosis-dependent and EGFR-, src-, or β-arrestin2-independent.