title: Diacylglycerol induces fusion of nuclear envelope membrane precursor vesicles.
abstract: Purified membrane vesicles isolated from sea urchin eggs form nuclear envelopes around sperm nuclei following GTP hydrolysis in the presence of cytosol. A low density subfraction of these vesicles (MV1), highly enriched in phosphatidylinositol (PtdIns), is required for nuclear envelope formation. Membrane fusion of MV1 with a second fraction that contributes most of the nuclear envelope can be initiated without GTP by an exogenous bacterial PtdIns-specific phospholipase C (PI-PLC) which hydrolyzes PtdIns to form diacylglycerides and inositol 1-phosphate. This PI-PLC hydrolyzes a subset of sea urchin membrane vesicle PtdIns into diglycerides enriched in long chain, polyunsaturated species as revealed by a novel liquid chromatography-mass spectrometry analysis. Large unilammelar vesicles (LUVs) enriched in PtdIns can substitute for MV1 in PI-PLC induced nuclear envelope formation. Moreover, MV1 prehydrolyzed with PI-PLC and washed to remove inositols leads to spontaneous nuclear envelope formation with MV2 without further PI-PLC treatment. LUVs enriched in diacylglycerol mimic prehydrolyzed MV1. These results indicate that production of membrane-destabilizing diglycerides in membranes enriched in PtdIns may facilitate membrane fusion in a natural membrane system and suggest that MV1, which binds only to two places on the sperm nucleus, may initiate fusion locally.
authors.affiliation: Biology Department, Amherst College, Amherst, Massachusetts 01002, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Barona
authors.forename: Richard D
authors.initials: RD
authors.lastname: Byrne
authors.forename: Trevor R
authors.initials: TR
authors.lastname: Pettitt
authors.forename: Michael J O
authors.initials: MJ
authors.lastname: Wakelam
authors.forename: Banafshe
authors.initials: B
authors.lastname: Larijani
authors.forename: Dominic L
authors.initials: DL
authors.lastname: Poccia
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002474:Cell-Free System; D002853:Chromatography, Liquid; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism*; D005306:Fertilization; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D008297:Male; D013058:Mass Spectrometry; D008954:Models, Biological; D009685:Nuclear Envelope / Q000378:metabolism; D010063:Ovum / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011485:Protein Binding; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D004075:Diglycerides; D008055:Lipids; D010716:Phosphatidylinositols; D014867:Water; D007294:Inositol; D006160:Guanosine Triphosphate; D010744:Phosphoric Monoester Hydrolases; D010738:Type C Phospholipases