RESUMO
G protein-coupled receptors (GPCRs) mediate signal transduction via G protein or β-arrestin. Several biased ligands and receptors that preferentially signal through either G protein- or β-arrestin-mediated pathways have been identified. These discoveries have redefined the classical GPCR signaling paradigm. Distinct ligand-receptor binding sites might be one of the main reasons for biased signal transduction. It is posited that multiple active conformations of receptors lead to distinct kinase phosphorylation patterns on C terminus of receptors. Phosphorylation patterns decide which signal pathway will be transduced. The biased signal pathway transduction has been found in more than 40 GPCRs till now. A few of them have been found involved in fine-regulation of physiological processes. However, most others still need further investigation. The biased ligands may be developed as tools for understanding the basic physiology of GPCR, and, potentially and most importantly, as fine-tuned therapeutics that maximize beneficial effects and minimize adverse or unwanted effects. These studies will provide new insights into new drug discovery.