Agonist-induced changes in RalA activities allows the prediction of the endocytosis of G protein-coupled receptors

• Published in: Biochimica et biophysica acta Vol. 1863; no. 1; pp. 77 - 90
• Main Authors: Zheng, Mei, Zhang, Xiaohan, Guo, Shuohan, Zhang, Xiaowei, Min, Chengchun, Cheon, Seung Hoon, Oak, Min-Ho, Kim, Young Ran, Kim, Kyeong-Man
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2016
• Subjects: Angiotensin; Endocytosis - physiology; Epsin; G-Protein-Coupled Receptor Kinase 2 - genetics; G-Protein-Coupled Receptor Kinase 2 - metabolism; HEK293 Cells; Humans; LPA; Protein Transport - physiology; ral GTP-Binding Proteins - genetics; ral GTP-Binding Proteins - metabolism; Receptors, Dopamine D2 - agonists; Receptors, Dopamine D2 - genetics; Receptors, Dopamine D2 - metabolism; Receptors, Lysophosphatidic Acid - agonists; Receptors, Lysophosphatidic Acid - genetics; Receptors, Lysophosphatidic Acid - metabolism; β-Adrenoceptor; β-Arrestin; β-Arrestin; β-Adrenoceptor; LPA; Epsin; Angiotensin
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/j.bbamcr.2015.10.007

GTP binding proteins are classified into two families: heterotrimeric large G proteins which are composed of three subunits, and one subunit of small G proteins. Roles of small G proteins in the intracellular trafficking of G protein-coupled receptors (GPCRs) were studied. Among various small G proteins tested, GTP-bound form (G23V) of RalA inhibited the internalization of dopamine D2 receptor independently of the previously reported downstream effectors of RalA, such as Ral-binding protein 1 and PLD. With high affinity for GRK2, active RalA inhibited the GPCR endocytosis by sequestering the GRK2 from receptors. When it was tested for several GPCRs including an endogenous GPCR, lysophosphatidic acid receptor 1, agonist-induced conversion of GTP-bound to GDP-bound RalA, which presumably releases the sequestered GRK2, was observed selectively with the GPCRs which have tendency to undergo endocytosis. Conversion of RalA from active to inactive state occurred by translocation of RGL, a guanine nucleotide exchange factor, from the plasma membrane to cytosol as a complex with Gβγ. These results suggest that agonist-induced Gβγ-mediated conversion of RalA from the GTP-bound form to the GDP-bound form could be a mechanism to facilitate agonist-induced internalization of GPCRs. [Display omitted] •A novel regulatory mechanism for the GPCR endocytosis is proposed.•The mechanism relies on activity-dependent interaction of GRK2 with active RalA.•Gβγ-mediated signaling pathway is involved in the regulation of RalA activities.•The occurrence of GPCR endocytosis can be predicted based on this mechanism.