G-protein-mediated signaling and its control in macrophages and mammalian cells.

G-protein coupled receptor (GPCR) in various cell types exert its effects through heterotrimetic GTP-binding proteins (G-proteins). The interaction of specific ligand or agonists with CPCR transuces signal and enhances gene expression, mitogen activated protein kinase (MAP kinase) activation, and thus regulates cell proliferation, differentation, and motility. Abnormal signaling or prolonged activation of G-protein signaling pathways blocks normal functioning of various cells and tissues of our body. New insights into the mechanisms governing the specificity and temporal regulation of G-protein signaling pathways have been provided by the recent discovery of GTPase-activating proteins (GAPs) and RGS proteins (regulators of G-protein signaling). Different molecular biological approaches are now being employed to study the G-protein-mediated signaling and its control in various mammalian cells. Recent developments on the activation of phagocytic cells, especially macrophages, via ligation or cross-linking of GPCR and their postreceptor ligation effect against several intramacrophage pathogens are also discussed.