High-precision FRET analysis of the G-protein coupled receptor TGR5 in live cells

Excerpt

TGR5 is a widely expressed and highly conserved G protein coupled receptor. Its activity and functionality is commonly modulated by bile acids, especially by lithocholic acid. As true for all ligand activated G protein coupled receptors a G protein subunit is released from TGR5 after ligand binding and initiates a signaling cascade resulting in a cell type specific response. Current investigations suggest an involvement of TGR5 in bile homeostasis, inflammatory responses and hepatobiliary diseases. Therefore a targeted therapy involving site specific inhibition of TGR5 is of immense interest. However, up to date no solved structure of TGR5 exists and oligomerization properties are largely unknown. To determine structural changes and oligomerization properties of TGR5 we designed a three way strategy including TGR5 plasmids coupled with (I) fluorescent proteins (FPs) at the C-terminus or (II) a N-terminal peptide tag (ACP) for subsequent labeling with a fluorescent dye and (III) unnatural amino acids (UAAs) for site specific extracellular labeling. …