GPCR Interacting Proteins.

The complex transduction of ligand stimulation events at G-protein coupled receptors (GPCRs) by heterotrimetric G proteins has long been appreciated. In addition to this, recent data shows that other protein interactions assist and can fine-tune cellular signals. Scientists have identified other membrane and intracellular proteins that interact, directly or indirectly, with GPCRs. In fact, 50 or more proteins are described in current literature as GPCR interactive proteins. GPCR interacting proteins act as modulators of ligand-evoked signals. Membrane associated or intracellular GPCR interacting proteins have critical roles in mediating: ligand recognition, optimization of signal transduction, trafficking, receptor clustering, and/or compartmentalization. This chapter reviews four aspects of the GPCR interacting protein literature: (a) methods for identifying GPCR interacting proteins; (b) interaction domains on the GPCR; (c) facilitation and fine-tuning of GPCR signaling events by interacting proteins; and (d) particular analysis of proteins that are μ opioid receptor (μOR) interactive. Although GPCR dimerization is viewed by many as a type of protein interaction between the GPCRs, dimer-related protein interactions will not be discussed; an alternate section of this book is devoted to dimerization. [ABSTRACT FROM AUTHOR]