title: Structural basis of dynamic membrane recognition by trans-Golgi network specific FAPP proteins.
abstract: Glycosphingolipid metabolism relies on selective recruitment of the pleckstrin homology (PH) domains of FAPP proteins to the trans-Golgi network. The mechanism involved is unclear but requires recognition of phosphatidylinositol-4-phosphate (PI4P) within the Golgi membrane. We investigated the molecular basis of FAPP1-PH domain interactions with PI4P bilayers in liposome sedimentation and membrane partitioning assays. Our data reveals a mechanism in which FAPP-PH proteins preferentially target PI4P-containing liquid disordered membranes, while liquid ordered membranes were disfavored. Additionally, NMR spectroscopy was used to identify the binding determinants responsible for recognizing trans-Golgi network-like bicelles including phosphoinositide and neighboring lipid molecules. Membrane penetration by the FAPP1-PH domain was mediated by an exposed, conserved hydrophobic wedge next to the PI4P recognition site and ringed by a network of complementary polar residues and basic charges. Our data illuminates how insertion of a structured loop provides selectivity for sensing membrane fluidity and targeting to defined membrane zones and organelles. The determinants of this membrane sensing process are conserved across the CERT, OSBP and FAPP family. Hence, lipid gradients not only result in differential membrane ordering along the secretory pathway but also specifically localize diverse proteins through recognition of ensembles of lipid ligands in dynamic and deformable bilayers in order to promote anterograde trafficking.
authors.affiliation: School of Cancer Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Marc
authors.initials: M
authors.lastname: Lenoir
authors.affiliation: Paul Langerhans Institute Dresden of the Helmholtz Centre Munich at the University Clinic and Medical Faculty Carl Gustav Carus, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany; German Center for Diabetes Research (Deutsches Zentrum für Diabetesforschung e.V.), Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
authors.forename: Michał
authors.initials: M
authors.lastname: Grzybek
authors.affiliation: Laboratory of Cytobiochemistry, Biotechnology Faculty, University of Wrocław, Przybyszewskiego 63-77, 51-148 Wrocław, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Majkowski
authors.affiliation: School of Cancer Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Sandya
authors.initials: S
authors.lastname: Rajesh
authors.affiliation: School of Cancer Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Jaswant
authors.initials: J
authors.lastname: Kaur
authors.affiliation: School of Cancer Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Sara B-M
authors.initials: SB
authors.lastname: Whittaker
authors.affiliation: Paul Langerhans Institute Dresden of the Helmholtz Centre Munich at the University Clinic and Medical Faculty Carl Gustav Carus, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany; German Center for Diabetes Research (Deutsches Zentrum für Diabetesforschung e.V.), Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
authors.forename: Ünal
authors.initials: Ü
authors.lastname: Coskun
authors.affiliation: School of Cancer Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. Electronic address: m.overduin@bham.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Overduin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D062105:Molecular Docking Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D020349:Surface Plasmon Resonance
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D006028:Glycosphingolipids; C487037:PLEKHA3 protein, human; C487038:PLEKHA8 protein, human; D018129:Phosphatidylinositol Phosphates; C037178:phosphatidylinositol 4-phosphate
keywords: lipid microdomains; membrane trafficking; nuclear magnetic resonance spectroscopy; phosphoinositide recognition; pleckstrin homology domain