title: GABAB receptor promotes its own surface expression by recruiting a Rap1-dependent signaling cascade.
abstract: G-protein-coupled receptors (GPCRs) are key players in cell signaling, and their cell surface expression is tightly regulated. For many GPCRs such as β2-AR (β2-adrenergic receptor), receptor activation leads to downregulation of receptor surface expression, a phenomenon that has been extensively characterized. By contrast, some other GPCRs, such as GABA(B) receptor, remain relatively stable at the cell surface even after prolonged agonist treatment; however, the underlying mechanisms are unclear. Here, we identify the small GTPase Rap1 as a key regulator for promoting GABA(B) receptor surface expression. Agonist stimulation of GABA(B) receptor signals through Gαi/o to inhibit Rap1GAPII (also known as Rap1GAP1b, an isoform of Rap1GAP1), thereby activating Rap1 (which has two isoforms, Rap1a and Rap1b) in cultured cerebellar granule neurons (CGNs). The active form of Rap1 is then recruited to GABA(B) receptor through physical interactions in CGNs. This Rap1-dependent signaling cascade promotes GABA(B) receptor surface expression by stimulating receptor recycling. Our results uncover a new mechanism regulating GPCR surface expression and also provide a potential explanation for the slow, long-lasting inhibitory action of GABA neurotransmitter.
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Zongyong
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China slhuang@mail.hust.edu.cn lisu@mail.hust.edu.cn jfliu@mail.hust.edu.cn.
authors.forename: Siluo
authors.initials: S
authors.lastname: Huang
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Yunyun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Yongjian
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Ninghua
authors.initials: N
authors.lastname: Sun
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Yilei
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Jiang
authors.affiliation: Department of Immunology and Cell Biology, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Nagahiro
authors.initials: N
authors.lastname: Minato
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université Montpellier 1 et 2, Montpellier cedex 5 34094, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pin
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China slhuang@mail.hust.edu.cn lisu@mail.hust.edu.cn jfliu@mail.hust.edu.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Su
authors.affiliation: Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China slhuang@mail.hust.edu.cn lisu@mail.hust.edu.cn jfliu@mail.hust.edu.cn.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D018080:Receptors, GABA-B / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D018080:Receptors, GABA-B; D020827:rap1 GTP-Binding Proteins
keywords: GABAB receptor; Internalization; Protein–protein interaction; Rap1; Recycling