Seven transmembrane receptors (7TM) in the view of dimerization and experimental methods to study their dimerization and cross-talk

Seven transmembrane (7TM) receptors constitute the largest and the most diverse superfamily of proteins encoded in the human genome comprising at least 850 putative members. These receptors are widely expressed in the body and play a fundamental role in physiology and pathophysiology. Not only do they regulate many physiological processes, but drugs that target these receptors and either activate or inactivate them, account for the most prosperous drugs sold worldwide. Of approximately 500 currently marketed drugs, more then 30 % are modulators of 7TM receptor function. In the last two decades, impressive progress in the understanding of 7TM receptor function has been achieved, though dimerization or oligomerization of 7TM receptors is still a novel and controversial concept. Although a large quantity of data, obtained by different biophysical, biochemical, structural and functional approaches e.g. coimunoprecipitation, Western blot, bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively) argue for dimerization or oligomerization of these receptors, several publications criticized the applied methods and challenged the concept. In this paper the main and the most important techniques are presented and complemented with our ideas.