The monomer/homodimer equilibrium of G protein-coupled receptors: Formation in the secretory pathway and potential functional significance

Abstract

In the last years, it became clear that the majority of the G protein-coupled receptors seem to be expressed not as exclusive monomers or homodimers, but in a monomer/homodimer equilibrium. Strikingly, monomers and homodimers of a specific receptor seem to interconvert dynamically. It is unclear at the moment, however, whether this equilibrium may undergo changes during receptor lifetime, how it is regulated and whether it has any functional significance. It was previously shown that G protein-coupled receptor homodimerization takes place in the endoplasmic reticulum and first data show that this may also hold true for equilibrium formation. This review addresses the limited available data for the monomer/homodimer equilibrium of these receptors. It also summarizes modern imaging methods which are useful to study these transient interactions at the plasma membrane and also in intracellular compartments.