G Protein-Coupled Receptors

The G protein-coupled receptors (GPCRs) constitute the largest superfamily of proteins encoded by the human genome. These receptors are membrane proteins which share a common structure of seven transmembrane helices and are involved in the cellular signal transduction through activation of heterotrimeric protein (G protein) in intracellular environment. This activation signal, mediated by the agonist binding to the extracellular domain of the receptor, is transmitted into the cell and activates many signaling cascades in different physiological events such as neurotransmission, growth, metabolism, differentiation of the cell, secretion and immune defense. As a consequence, these receptors are described as therapeutic targets for more than 50% of drugs sold worldwide. Thus, the study of the molecular mechanism involving GPCRs has become essential to understand the cellular signaling and, consequently, the rational design of new therapeutic agents, e.g. antihypertensive drugs. Therefore, this review reports the structural characteristics, the activation mechanism, the G protein activation and the classification of these membrane proteins of huge physiological and pathophysiological importance.