Cell surface receptors belonging to the family of G protein coupled receptors (GPCRs) – also known as seven-transmembrane, heptahelical or serpentine, receptors – are involved in the regulation of diverse signaling processes. Heterotrimeric G proteins, consisting of α, β, and γ-subunits provide the signal coupling mechanisms to this superfamily of receptors. The role of the heptahelical receptors and their G proteins in signaling mechanisms involving sensory transduction as well as cell homeostasis has been known for almost three decades. However, only in the recent days, their critical role in the regulation of cell growth has been identified. The identification of newer heptahelical receptors as well as G protein subunits has contributed towards the greater understanding of the novel mechanisms through which these receptors recruit G proteins and small GTPases in regulating cell growth. The compendium of reviews presented here focuses on the mechanisms by which the different components of the heptahelical receptors signaling unit, namely the receptors, the G protein subunits, and their effectors regulate the critical signaling events involved in cell growth, differentiation, and apoptosis. In the reviews presented here, the authors bring their unique perspective to describe the possible mechanisms by which signaling pathways regulated by G protein coupled receptors and G proteins contribute to signal networking involved in cell growth, differentiation and apoptosis.
Signaling by GPCRs is initiated by a specific ligand β that binds and activates the receptor inducing a conformational change in the receptor. The receptor, thus activated, stimulates a specific G protein by catalyzing the exchange of guanine nucleotides in the α-subunit. The GTP-bound α-subunit and the βα subunits disassociate from the receptor and activate their respective down-stream effector proteins. The first six articles from this compendium analyse the signaling events from the vantage point of the GPCRs. The following two articles describe the variations of the common theme exhibited by two novel families of GPCRs namely, the PAR and the virally encoded GPCRs. Two articles that discuss the intracellular communication networking initiated by GPCRs involving receptor tyrosine kinases, non-receptor tyrosine kinases, and STATs follow this. As the signal from GPCR progresses to the G proteins, the next series of seven reviews discusses the mechanisms by which different G proteins transduce the signals from the receptors to the downstream effector molecules.
This is a preview of subscription content, access via your institution