title: Intracellular curvature-generating proteins in cell-to-cell fusion.
abstract: Cell-to-cell fusion plays an important role in normal physiology and in different pathological conditions. Early fusion stages mediated by specialized proteins and yielding fusion pores are followed by a pore expansion stage that is dependent on cell metabolism and yet unidentified machinery. Because of a similarity of membrane bending in the fusion pore rim and in highly curved intracellular membrane compartments, in the present study we explored whether changes in the activity of the proteins that generate these compartments affect cell fusion initiated by protein fusogens of influenza virus and baculovirus. We raised the intracellular concentration of curvature-generating proteins in cells by either expressing or microinjecting the ENTH (epsin N-terminal homology) domain of epsin or by expressing the GRAF1 (GTPase regulator associated with focal adhesion kinase 1) BAR (Bin/amphiphysin/Rvs) domain or the FCHo2 (FCH domain-only protein 2) F-BAR domain. Each of these treatments promoted syncytium formation. Cell fusion extents were also influenced by treatments targeting the function of another curvature-generating protein, dynamin. Cell-membrane-permeant inhibitors of dynamin GTPase blocked expansion of fusion pores and dominant-negative mutants of dynamin influenced the syncytium formation extents. We also report that syncytium formation is inhibited by reagents lowering the content and accessibility of PtdIns(4,5)P(2), an important regulator of intracellular membrane remodelling. Our findings indicate that fusion pore expansion at late stages of cell-to-cell fusion is mediated, directly or indirectly, by intracellular membrane-shaping proteins.
authors: Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA.
authors: Jean-Philippe
authors: JP
authors: Richard
authors: Evgenia
authors: E
authors: Leikina
authors: Ralf
authors: R
authors: Langen
authors: William Mike
authors: WM
authors: Henne
authors: Margarita
authors: M
authors: Popova
authors: Tamas
authors: T
authors: Balla
authors: Harvey T
authors: HT
authors: McMahon
authors: Michael M
authors: MM
authors: Kozlov
authors: Leonid V
authors: LV
authors: Chernomordik
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002459:Cell Fusion; D002462:Cell Membrane / Q000648:ultrastructure*; D034281:Dynamins / Q000378:metabolism; D015726:Giant Cells / Q000502:physiology; D006389:Hemagglutinins, Viral / Q000502:physiology; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D006389:Hemagglutinins, Viral; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; C114154:epsin; C458881:hemagglutinin fusogenic peptide, influenza virus; D034281:Dynamins