Figure 5

Visualization of GPCRs by a fluorescent agonist (A; green) or a fluorescent antagonist (A; red). Fluorescent agonists induce receptor internalization to intracellular endosomes as demonstrated by SK-N-MC cells, endogenously expressing the human Y₁ receptor, incubated with CF-labeled neuropeptide Y (B; NPY in green, nuclei in blue, bar represents 10 μm). In contrast, fluorescent antagonists prevent receptor trafficking to intracellular compartments and target receptors at the cell membrane as shown by Schneider et al. using MCF-7 cells, endogenously expressing the Y₁ receptor, incubated with Py-1-labeled Y₁R antagonist derived from BIBP3226 [112].