title: Spatial regulation of membrane fusion controlled by modification of phosphoinositides.
abstract: Membrane fusion plays a central role in many cell processes from vesicular transport to nuclear envelope reconstitution at mitosis but the mechanisms that underlie fusion of natural membranes are not well understood. Studies with synthetic membranes and theoretical considerations indicate that accumulation of lipids characterised by negative curvature such as diacylglycerol (DAG) facilitate fusion. However, the specific role of lipids in membrane fusion of natural membranes is not well established. Nuclear envelope (NE) assembly was used as a model for membrane fusion. A natural membrane population highly enriched in the enzyme and substrate needed to produce DAG has been isolated and is required for fusions leading to nuclear envelope formation, although it contributes only a small amount of the membrane eventually incorporated into the NE. It was postulated to initiate and regulate membrane fusion. Here we use a multidisciplinary approach including subcellular membrane purification, fluorescence spectroscopy and Förster resonance energy transfer (FRET)/two-photon fluorescence lifetime imaging microscopy (FLIM) to demonstrate that initiation of vesicle fusion arises from two unique sites where these vesicles bind to chromatin. Fusion is subsequently propagated to the endoplasmic reticulum-derived membranes that make up the bulk of the NE to ultimately enclose the chromatin. We show how initiation of multiple vesicle fusions can be controlled by localised production of DAG and propagated bidirectionally. Phospholipase C (PLCgamma), GTP hydrolysis and (phosphatidylinsositol-(4,5)-bisphosphate (PtdIns(4,5)P(2)) are required for the latter process. We discuss the general implications of membrane fusion regulation and spatial control utilising such a mechanism.
authors.affiliation: Cell Biophysics Laboratory, Lincoln's Inn Fields Laboratories, Cancer Research UK, London, United Kingdom.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Dumas
authors.forename: Richard D
authors.initials: RD
authors.lastname: Byrne
authors.forename: Ben
authors.initials: B
authors.lastname: Vincent
authors.forename: Tina M C
authors.initials: TM
authors.lastname: Hobday
authors.forename: Dominic L
authors.initials: DL
authors.lastname: Poccia
authors.forename: Banafshé
authors.initials: B
authors.lastname: Larijani
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D047331:Lytechinus / Q000166:cytology; D008297:Male; D008561:Membrane Fusion / Q000187:drug effects; D008856:Microscopy, Fluorescence; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology
chemical_list: D002843:Chromatin; D004075:Diglycerides; D004791:Enzyme Inhibitors; D004963:Estrenes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D006160:Guanosine Triphosphate; D051966:Phospholipase C gamma; D020558:GTP Phosphohydrolases
references.citation: Annu Rev Biophys. 2009;38:107-24
references.pmid: 19416062
references.citation: J Biol Chem. 2005 Dec 16;280(50):41171-7
references.pmid: 16216883
references.citation: Adv Enzyme Regul. 2009;49(1):148-56
references.pmid: 19344633
references.citation: Biochem J. 2009 Mar 1;418(2):233-46
references.pmid: 19196244
references.citation: Biochemistry. 2000 Nov 21;39(46):14012-8
references.pmid: 11087348
references.citation: Phys Rev Lett. 2005 May 13;94(18):181103
references.pmid: 15904354
references.citation: Nat Rev Mol Cell Biol. 2001 Oct;2(10):721-30
references.pmid: 11584299
references.citation: Cell Signal. 2007 May;19(5):913-22
references.pmid: 17184973
references.citation: Exp Cell Res. 1993 Mar;205(1):126-33
references.pmid: 8453987
references.citation: Dev Biol. 1994 Apr;162(2):568-78
references.pmid: 8150215
references.citation: PLoS One. 2009;4(1):e4255
references.pmid: 19165341
references.citation: Nat Struct Mol Biol. 2008 Jul;15(7):675-83
references.pmid: 18596814
references.citation: J Cell Sci. 1996 Jun;109 ( Pt 6):1275-83
references.pmid: 8799817
references.citation: Dev Biol. 1995 May;169(1):123-35
references.pmid: 7750633
references.citation: Eur J Cell Biol. 1996 Sep;71(1):22-32
references.pmid: 8884175
references.citation: Biochem J. 2005 Apr 15;387(Pt 2):393-400
references.pmid: 15554872
references.citation: Methods Mol Biol. 2009;464:207-23
references.pmid: 18951187
references.citation: FEBS Lett. 2004 Oct 8;576(1-2):9-13
references.pmid: 15474001
references.citation: Biochem J. 2001 Jun 1;356(Pt 2):495-501
references.pmid: 11368777
references.citation: Methods Cell Biol. 1998;53:417-52
references.pmid: 9348519
references.citation: J Cell Biol. 1991 Sep;114(5):929-40
references.pmid: 1874789
references.citation: Nat Rev Mol Cell Biol. 2009 Apr;10(4):287-92
references.pmid: 19277045