title: Pivotal role of extended linker 2 in the activation of Gα by G protein-coupled receptor.
abstract: G protein-coupled receptors (GPCRs) relay extracellular signals mainly to heterotrimeric G-proteins (Gαβγ) and they are the most successful drug targets. The mechanisms of G-protein activation by GPCRs are not well understood. Previous studies have revealed a signal relay route from a GPCR via the C-terminal α5-helix of Gα to the guanine nucleotide-binding pocket. Recent structural and biophysical studies uncover a role for the opening or rotating of the α-helical domain of Gα during the activation of Gα by a GPCR. Here we show that β-adrenergic receptors activate eight Gαs mutant proteins (from a screen of 66 Gαs mutants) that are unable to bind Gβγ subunits in cells. Five of these eight mutants are in the αF/Linker 2/β2 hinge region (extended Linker 2) that connects the Ras-like GTPase domain and the α-helical domain of Gαs. This extended Linker 2 is the target site of a natural product inhibitor of Gq. Our data show that the extended Linker 2 is critical for Gα activation by GPCRs. We propose that a GPCR via its intracellular loop 2 directly interacts with the β2/β3 loop of Gα to communicate to Linker 2, resulting in the opening and closing of the α-helical domain and the release of GDP during G-protein activation.
authors.affiliation: From the Department of Physiology, Cornell University Weill Medical College, New York, New York 10065.
authors.forename: Jianyun
authors.initials: J
authors.lastname: Huang
authors.affiliation: From the Department of Physiology, Cornell University Weill Medical College, New York, New York 10065.
authors.forename: Yutong
authors.initials: Y
authors.lastname: Sun
authors.affiliation: From the Department of Physiology, Cornell University Weill Medical College, New York, New York 10065.
authors.forename: J Jillian
authors.initials: JJ
authors.lastname: Zhang
authors.affiliation: From the Department of Physiology, Cornell University Weill Medical College, New York, New York 10065 xyhuang@med.cornell.edu.
authors.forename: Xin-Yun
authors.initials: XY
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011943:Receptors, Adrenergic, beta / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D011943:Receptors, Adrenergic, beta; D011994:Recombinant Proteins; D019205:GTP-Binding Protein alpha Subunits, Gs
keywords: Cell Biology; Cell Signaling; Second Messenger; Signal Transduction; Signaling