Loss of balance in normal GPCR-mediated cell trafficking.

G protein-coupled receptors (GPCRs) form a most diverse family of integral membrane proteins that mediate homeostatic and pathological processes, most notably by orchestrating cell distribution throughout the body, their infiltration, and time of presence in inflamed tissues. Here we discuss loss-of-orientation-effects in GPCR-mediated cell trafficking and migration and their impact on the phenotype of autoimmune diseases. In this context, we provide a systemic and integrative view of the contribution of abnormal GPCR expression as well as the levels of natural ligands and functional autoantibodies to the phenotype of autoimmune diseases. Currently, several studies propose that functional autoantibodies (including those targeting GPCRs) constitute an exclusively pathogenic or pathognomonic phenomenon. Here we reinforce the need of revising this point of view, and suggest that functional autoantibodies primary play a role in normal human physiology, while dysregulation of their functions causes autoimmune disease. Because patients with autoimmune diseases still suffer from severe morbidity and mortality rates, we consider expanding our knowledge on (patho)physiological roles of GPCR as a prerequisite for the development of novel specific therapeutic modalities.