Cover Caption

About the cover: Rapid agonist-induced sequestration of a GFP-tagged β2-adrenergic receptor. A fusion protein was constructed that consisted of the S65T mutant of green fluorescent protein (GFP) attached to the carboxyl terminus of the β2-adrenergic receptor. The GFP tag did not interfere with ligand recognition, G protein coupling or internalization. Left, when expressed in HEK 293 cells, receptor is distributed diffusely over the surface membrane. Right, 5 min after exposure to 10 µM isoproterenol, receptors are internalized within endosomal vesicular membranes. The left and right panels are two different cells representative of control and agonist-treated populations. From Barak, L. S., S. S. G. Ferguson, J. Zhang, C. Martenson, T. Meyer, and M. C. Caron. Internal trafficking and surface mobility of a functionally intact β2-adrenergic receptor-green fluorescent protein conjugate. Mol. Pharmacol. 51:177-184 (1997).