title: Structural basis for different phosphoinositide specificities of the PX domains of sorting nexins regulating G-protein signaling.
abstract: Sorting nexins (SNXs) or phox homology (PX) domain containing proteins are central regulators of cell trafficking and signaling. A subfamily of PX domain proteins possesses two unique PX-associated domains, as well as a regulator of G protein-coupled receptor signaling (RGS) domain that attenuates Gαs-coupled G protein-coupled receptor signaling. Here we delineate the structural organization of these RGS-PX proteins, revealing a protein family with a modular architecture that is conserved in all eukaryotes. The one exception to this is mammalian SNX19, which lacks the typical RGS structure but preserves all other domains. The PX domain is a sensor of membrane phosphoinositide lipids and we find that specific sequence alterations in the PX domains of the mammalian RGS-PX proteins, SNX13, SNX14, SNX19, and SNX25, confer differential phosphoinositide binding preferences. Although SNX13 and SNX19 PX domains bind the early endosomal lipid phosphatidylinositol 3-phosphate, SNX14 shows no membrane binding at all. Crystal structures of the SNX19 and SNX14 PX domains reveal key differences, with alterations in SNX14 leading to closure of the binding pocket to prevent phosphoinositide association. Our findings suggest a role for alternative membrane interactions in spatial control of RGS-PX proteins in cell signaling and trafficking.
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Caroline
authors.initials: C
authors.lastname: Mas
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Suzanne J
authors.initials: SJ
authors.lastname: Norwood
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bugarcic
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Genevieve
authors.initials: G
authors.lastname: Kinna
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Natalya
authors.initials: N
authors.lastname: Leneva
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Oleksiy
authors.initials: O
authors.lastname: Kovtun
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ghai
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Lorena E
authors.initials: LE
authors.lastname: Ona Yanez
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Jasmine L
authors.initials: JL
authors.lastname: Davis
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Rohan D
authors.initials: RD
authors.lastname: Teasdale
authors.affiliation: From the Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia b.collins@imb.uq.edu.au.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Collins
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002465:Cell Movement; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018129:Phosphatidylinositol Phosphates / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D058305:Sorting Nexins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; C000594709:SNX14 protein, human; C524095:Snx19 protein, mouse; D058305:Sorting Nexins; C055525:phosphatidylinositol 3-phosphate; D019204:GTP-Binding Proteins
keywords: Cell Signaling; Endosome; G Protein-coupled Receptor (GPCR); Membrane Trafficking; Phosphatidylinositol; Phox Homology Domain; Regulator of G Protein Signaling (RGS); Scaffold protein; Sorting Nexin; X-ray Crystallography