Dynamics and Structural Features Affecting Arrestin Function

Abstract

Arrestin proteins are key regulators of G-protein mediated signaling. Ligand activated G-Protein Coupled Receptors (GPCRs) are rapidly phosphorylated and subsequently bind to arrestins with high affinity. The role of arrestin in attenuating G-protein signaling is three fold. The binding of arrestin sterically hinders G-protein activation by the GPCRs. æIt recruits 2nd messenger-degrading enzymes and it also mediates receptor internalization. Together these events reduce the capacity for 2nd messenger signaling and have been consistently associated with the onset of drug tolerance after prolonged exposure. In addition, arrestins have also been shown to facilitate G-protein independent signaling. Arrestins act as a scaffold for several MAP kinases and have been linked to both the ERK and JNK signaling pathways. Activation of these signaling pathways can lead to several downstream outcomes including chemotaxis, inflammation, and increased cellular proliferation. æThe structural details that allow arrestin to fulfill these roles have not been elucidated. We have developed biophysical methods that allow us to closely examine the underlying mode of action. Several mutant forms of arrestin have been constructed and isotopically labeled using a specific scheme that simplifies the NMR spectra of this 48kDa protein. æWith this scheme we can probe the structure and dynamics of the protein by NMR spectroscopy in order to better understand its function. This information could lead to the development of ligands that modulate arrestin function and therefore serve as useful tools in pharmacological discoveries and potentially lead to new therapeutic paradigms. ææThis work was supported by NIH/NIDA grants DA3801, DA9152, DA26533