Regulation of G-protein signaling by RKTG via sequestration of the G betagamma subunit to the Golgi apparatus.
Upon ligand binding, G-protein-coupled receptors (GPCRs) impart the signal to heterotrimeric G proteins composed of alpha, beta, and gamma subunits, leading to dissociation of the G alpha subunit from the G betagamma subunit. While the G alpha subunit is imperative for downstream signaling, the G betagamma subunit, in its own right, mediates a variety of cellular responses such as GPCR desensitization via recruiting GRK to the plasma membrane and AKT stimulation. Here we report a mode of spatial regulation of the G betagamma subunit through alteration in subcellular compartmentation. RKTG (Raf kinase trapping to Golgi apparatus) is a newly characterized membrane protein specifically localized at the Golgi apparatus. The N terminus of RKTG interacts with G beta and tethers G betagamma to the Golgi apparatus. Overexpression of RKTG impedes the interaction of G betagamma with GRK2, abrogates the ligand-induced change of subcellular distribution of GRK2, reduces isoproterenol-stimulated phosphorylation of the beta2-adrenergic receptor (beta 2AR), and alters beta 2AR desensitization. In addition, RKTG inhibits G betagamma- and ligand-mediated AKT phosphorylation that is enhanced in cells with downregulation of RKTG. Silencing of RKTG also alters GRK2 internalization and compromises ligand-induced G beta translocation to the Golgi apparatus. Taken together, our results reveal that RKTG can modulate GPCR signaling through sequestering G betagamma to the Golgi apparatus and thereby attenuating the functions of G betagamma.
Jiang
Yuhui
Y
Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 294 Taiyuan Rd., Shanghai 200031, China.
Xie
Xiaoduo
X
Zhang
Yixuan
Y
Luo
Xiaolin
X
Wang
Xiao
X
Fan
Fengjuan
F
Zheng
Dawei
D
Wang
Zhenzhen
Z
Chen
Yan
Y
D000818:Animals; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D054768:G-Protein-Coupled Receptor Kinases / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D020868:Gene Silencing; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008024:Ligands; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008565:Membrane Proteins; C532354:PAQR3 protein, human; D018343:Receptors, Adrenergic, beta-2; D051057:Proto-Oncogene Proteins c-akt; D054768:G-Protein-Coupled Receptor Kinases