biomolecules Review Receptor-Arrestin Interactions: The GPCR Perspective Mohammad Seyedabadi 1,2 , Mehdi Gharghabi 3, Eugenia V. Gurevich 4 and Vsevolod V. Gurevich 4,* 1 Department of Toxicology & Pharmacology, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari 48471-93698, Iran;
[email protected] 2 Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari 48167-75952, Iran 3 Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA;
[email protected] 4 Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA;
[email protected] * Correspondence:
[email protected]; Tel.: +1-615-322-7070; Fax: +1-615-343-6532 Abstract: Arrestins are a small family of four proteins in most vertebrates that bind hundreds of different G protein-coupled receptors (GPCRs). Arrestin binding to a GPCR has at least three functions: precluding further receptor coupling to G proteins, facilitating receptor internalization, and initiating distinct arrestin-mediated signaling. The molecular mechanism of arrestin–GPCR interactions has been extensively studied and discussed from the “arrestin perspective”, focusing on the roles of arrestin elements in receptor binding. Here, we discuss this phenomenon from the “receptor perspective”, focusing on the receptor elements involved in arrestin binding and empha- sizing existing gaps in our knowledge that need to be filled. It is vitally important to understand the role of receptor elements in arrestin activation and how the interaction of each of these elements with arrestin contributes to the latter’s transition to the high-affinity binding state. A more precise knowledge of the molecular mechanisms of arrestin activation is needed to enable the construction of arrestin mutants with desired functional characteristics.