More than 800 G protein-coupled receptors (GPRs) are transcribed in the human genome (1). For many of these receptors, no endogenous ligand has been found, and, therefore, they are currently designated as orphan receptors. One such protein, GPR30, has been proposed to be an estrogen receptor (ER) (2, 3). GPR30 has been localized either to the cell plasma membrane (2) or to the endoplasmic retic...
