Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 61186, Republic of Korea.
Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 61186, Republic of Korea.
Biochem Pharmacol. 2020 Aug;178:114049. doi: 10.1016/j.bcp.2020.114049. Epub 2020 May 23.
The fate and activity of β-arrestin2, a key player in the regulation of desensitization and endocytosis of G protein-coupled receptors (GPCRs), are regulated by mouse double minute 2 homolog (Mdm2)-mediated ubiquitination. However, details of the molecular mechanisms of β-arrestin2 ubiquitination remain unclear. Studies on β-arrestin2 and Mdm2 mutants with modified nucleocytoplasmic shuttling properties have revealed that β-arrestin2 ubiquitination occurs in the nucleus in a Gβγ- and clathrin-dependent manner. The nuclear entry of both β-arrestin2 and Mdm2 commonly relies on the presence of importin complex but can occur independently of each other. Gβγ and clathrin regulated the nuclear entry of β-arrestin2 by mediating the interaction between β-arrestin2 and importin β1. In contrast, Akt-mediated phosphorylation of two serine residues of Mdm2 partly regulated the nuclear entry of Mdm2. Ubiquitinated β-arrestin2 along with Mdm2 translocated to the cytoplasm where they play various functional roles including receptor endocytosis and ubiquitination of other cytoplasmic proteins. The nuclear export of Mdm2 required nuclear entry and interaction of β-arrestin2 with Mdm2. Ubiquitination was required for the translocation of β-arrestin2 toward activated receptors on the plasma membrane and for its endocytic activity. The current study revealed the cellular components and processes involved in the ubiquitination of β-arrestin2, and these findings could be quintessential for providing directions and detailed strategies for the manipulation of GPCR functions and development of GPCR-related therapeutics.
β-arrestin2 是调节 G 蛋白偶联受体（GPCR）脱敏和内吞作用的关键因子，其命运和活性受鼠双微体 2 同源物（Mdm2）介导的泛素化调节。然而，β-arrestin2 泛素化的分子机制细节尚不清楚。对具有修饰的核质穿梭特性的β-arrestin2 和 Mdm2 突变体的研究表明，β-arrestin2 的泛素化在细胞核中以 Gβγ 和网格蛋白依赖性的方式发生。β-arrestin2 和 Mdm2 的核输入都通常依赖于输入蛋白复合物的存在，但可以彼此独立发生。Gβγ 和网格蛋白通过调节β-arrestin2 与输入蛋白β1 的相互作用来调节β-arrestin2 的核输入。相比之下，Akt 介导的 Mdm2 两个丝氨酸残基的磷酸化部分调节了 Mdm2 的核输入。泛素化的β-arrestin2 与 Mdm2 一起转移到细胞质中，在那里它们发挥各种功能作用，包括受体内吞和其他细胞质蛋白的泛素化。Mdm2 的核输出需要核内输入和β-arrestin2 与 Mdm2 的相互作用。泛素化对于β-arrestin2 向质膜上激活的受体的易位及其内吞活性是必需的。本研究揭示了β-arrestin2 泛素化涉及的细胞成分和过程，这些发现对于提供操纵 GPCR 功能和开发 GPCR 相关治疗的方向和详细策略可能至关重要。
