STKE Focus Issue on GPCRs: The Evolution of G Protein-Coupled Receptor Signaling

Abstract

G protein-coupled receptors (GPCRs) are one of the largest families of signaling proteins and are characterized by the presence of seven transmembrane domains and their ability to activate the heterotrimeric guanosine triphosphate (GTP) binding proteins (G proteins). Through the coupling to G proteins, GPCRs can mediate many different cellular effects and regulate processes as different as mitogenesis, cell movement, and cellular excitability. The original dogma about GPCR signaling was a fairly simple straightforward model in which each individual GPCR activated a single class of G protein. Furthermore, the G proteins had a high intrinsic GTPase activity and were initially believed not to utilize auxiliary regulators like those identified for the small GTPases. However, over time, the GPCR signaling field has gained in complexity, with GPCRs interacting with one another and other plasma membrane receptors, individual receptors coupling to more than one type of G protein, and the G proteins being regulated by GTPase activating proteins (GAPs). The STKE has information relevant to many aspects of G protein signaling and includes Reviews, Perspectives, Protocols, Connections Maps, relevant meetings in the Events section of the site, and other Web sites in the ST on the Web section of the site. If you are looking for others interested in G protein signaling, there are many people and labs in the Directory that list GPCRs as a focus of their research. Three new articles this issue highlight some of the changing views in the GPCR field. The ability and consequences of GPCRs coupling to more than one G protein is the subject of the review by Xiao ( ). GPCR multimerization is the topic of the perspective by Thelen and Baggiolini ([http://stke.sciencemag.org/cgi/content/full/sigtrans;2001/104/pe3][1]). The role of regulators of G protein signaling (RGS) in connecting GPCRs to other receptors and membrane proteins is the topic of the review by Druey ( ). Xiao focuses on the coupling of β-adrenergic receptors in the heart and the consequences of the dual coupling of the β2 subtype to both Gi and Gs pathways in terms of signal compartmentalization and cell survival signaling. These effects have important physiological ramifications when considering the underlying pathologies associated with cardiac heart failure and therapeutic approaches for treatment. GPCRs can oligomerize with other GPCR or with other types of receptors, such as ligand-gated ion channels. The direct interaction between GPCRs and ligand-gated ion channels is the topic of a perspective from the STKE archive by Brandon and Moss ( ). In this issue, Thelen and Bagglioni critically evaluate whether chemokine receptors heterodimerize or homodimerize and whether the multimerization is physiologically important. Druey focuses on the G proteins themselves. RGS proteins enhance the rate of GTPase activity of the Gα subunit. RGS proteins have additional protein-protein interaction motifs through which they couple G protein signaling to other membrane proteins, such as N-type calcium channels, receptor tyrosine kinases, and ephrin B proteins. For those interested in understanding the basics of GPCR signaling, the STKE has three Connections Maps by Pathway Authority R. Iyengar and members of his laboratory. These are Canonical Pathways that describe the signaling cascades initiated by Gs ([http://stke.sciencemag.org/cgi/cm/CMP_6634][2]), Gq ([http://stke.sciencemag.org/cgi/cm/CMP_6680][2]), and Gi ([http://stke.sciencemag.org/cgi/cm/CMP_7430][2]). The pathway highlighted in this issue, the Gαi Pathway ([http://stke.sciencemag.org/cgi/cm/CMP_7430][2]), describes the signaling from both the activated α subunits and the βγ subunits. Featured in This Focus Issue on GPCRs Related Resources at STKE [1]: http://stke.sciencemag.org/cgi/content/full/sigtrans;2001/104/pe4 [2]: pending:yes