Biomolecules & Therapeutics  https://doi.org/10.4062/biomolther.2023.033
Biased Dopamine D2 Receptors Exhibit Distinct Intracellular Trafficking Properties and ERK Activation in Different Subcellular Domains
Shujie Wang†, Lulu Peng† and Kyeong-Man Kim*
Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
*E-mail: kmkim@jnu.ac.kr
Tel: +82-62-530-2936, Fax: +82-62-530-2949
†The first two authors contributed equally to this work.
Received: February 19, 2023; Revised: June 18, 2023; Accepted: June 27, 2023; Published online: July 19, 2023.
© The Korean Society of Applied Pharmacology. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Biased signaling or functional selectivity refers to the ability of an agonist or receptor to selectively activate a subset of transducers such as G protein and arrestin in the case of G protein-coupled receptors (GPCRs). Although signaling through arrestin has been reported from various GPCRs, only a few studies have examined side-by-side how it differs from signaling via G protein. In this study, two signaling pathways were compared using dopamine D2 receptor (D2R) mutants engineered via the evolutionary tracer method to selectively transduce signals through G protein or arrestin (D2G and D2Arr, respectively). D2G mediated the inhibition of cAMP production and ERK activation in the cytoplasm. D2Arr, in contrast, mediated receptor endocytosis accompanied by arrestin ubiquitination and ERK activation in the nucleus as well as in the cytoplasm. D2Arr-mediated ERK activation occurred in a manner dependent on arrestin3 but not arrestin2, accompanied by the nuclear translocation of arrestin3 via importin1. D2R-mediated ERK activation, which occurred in both the cytosol and nucleus, was limited to the cytosol when cellular arrestin3 was depleted. This finding supports the results obtained with D2Arr and D2G. Taken together, these observations indicate that biased signal transduction pathways activate distinct downstream mechanisms and that the subcellular regions in which they occur could be different when the same effectors are involved. These findings broaden our understanding on the relation between biased receptors and the corresponding downstream signaling, which is critical for elucidating the functional roles of biased pathways.
Keywords: Dopamine D2 receptor, Biased receptor, Endocytosis, Ubiquitination, ERK, importin

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