G-protein-coupled receptors and signaling networks: emerging paradigms

G-protein-coupled receptors (GPCRs) constitute the largest family of cell-s urface molecules involved in signal transmission, These receptors play key physiological roles and their dysfunction results in several diseases. Rece ntly, it has been shown that many of the cellular responses mediated by GPC Rs do not involve the sole stimulation of conventional second-messenger-gen erating systems, but instead result from the functional integration of an i ntricate network of intracellular signaling pathways. Effecters for GPCRs t hat are independent oi G proteins have now also been identified, thus chang ing the conventional view of the GPCR-heterotrimeric-G-protein-associated e ffector. The emerging information is expected to help elucidate the most ba sic mechanism by which these receptors exert their numerous physiological r oles, in addition to determining why the perturbation of their function res ults in many pathological conditions.