title: StarD7 behaves as a fusogenic protein in model and cell membrane bilayers.
abstract: StarD7 is a surface active protein, structurally related with the START lipid transport family. So, the present work was aimed at elucidating a potential mechanism of action for StarD7 that could be related to its interaction with a lipid-membrane interface. We applied an assay based on the fluorescence de-quenching of BD-HPC-labeled DMPC-DMPS 4:1 mol/mol SUVs (donor liposomes) induced by the dilution with non-labeled DMPC-DMPS 4:1 mol/mol LUVs (acceptor liposomes). Recombinant StarD7 accelerated the dilution of BD-HPC in a concentration-dependent manner. This result could have been explained by either a bilayer fusion or monomeric transport of the labeled lipid between donor and acceptor liposomes. Further experiments (fluorescence energy transfer between DPH-HPC/BD-HPC, liposome size distribution analysis by dynamic light scattering, and the multinuclear giant cell formation induced by recombinant StarD7) strongly indicated that bilayer fusion was the mechanism responsible for the StarD7-induced lipid dilution. The efficiency of lipid dilution was dependent on StarD7 electrostatic interactions with the lipid-water interface, as shown by the pH- and salt-induced modulation. Moreover, this process was favored by phosphatidylethanolamine which is known to stabilize non-lamellar phases considered as intermediary in the fusion process. Altogether these findings allow postulate StarD7 as a fusogenic protein.
authors: Biofísica-Química, Cátedra de Química Biológica, Físicas y Naturales, Argentina.
authors: Sofía
authors: S
authors: Angeletti
authors: Julieta M
authors: JM
authors: Sanchez
authors: Larry W
authors: LW
authors: Chamley
authors: Susana
authors: S
authors: Genti-Raimondi
authors: María A
authors: MA
authors: Perillo
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D015726:Giant Cells / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D050576:Membrane Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity
chemical_list: D002352:Carrier Proteins; D008051:Lipid Bilayers; D008081:Liposomes; D050576:Membrane Fusion Proteins; D011994:Recombinant Proteins; C483475:STARD7 protein, human