Diacylglycerol effects on phosphatidylinositol‐specific phospholipase C activity and vesicle fusion

Villar, Ana V.; Goñi, Félix M.; Alonso, Alicia

doi:10.1016/s0014-5793(01)02333-x

Cited by 35 publications

(27 citation statements)

References 21 publications

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“…This type of phase transition induces a localized destabilization of the membrane structure, which in turn favors membrane fusion. That DAG can lead to membrane fusion is supported by several reports using synthetic membrane systems treated with PLCs (17,19,20).…”

Section: Mv2 Inducers Envelope Formation Inhibitorsmentioning

confidence: 76%

“…The hydrolysis products of PtdIns catalyzed by the bacterial PI-PLC are diglycerides (normally DAG) and inositol 1-phosphate (from the intermediate D-myo-inositol-1,2-cyclic phosphate) (16). DAG produced enzymatically by phospholipases acting on synthetic membranes has been shown to be membrane destabilizing and induce membrane fusion (17)(18)(19)(20).We show here that under fusion-stimulating conditions, bacterial PI-PLC treatment of sea urchin egg membranes results in large increases of a small subset of diradylglyceride (diacylglycerol, alkylacylglycerol, and alkenylacylglycerol) molecular species, in particular, DAG 18:0/20:4. To test whether fusion of natural membranes induced by PI-PLC in our cell-free system might result from localized production of DAG, we took two complementary approaches.…”

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confidence: 67%

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confidence: 99%

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Diacylglycerol Induces Fusion of Nuclear Envelope Membrane Precursor Vesicles

Barona

Byrne

Pettitt

et al. 2005

Journal of Biological Chemistry

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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.At the end of each mitosis in eukaryotes, the nuclear envelope is typically reconstituted by membrane fusion, forming the nuclear compartment and segregating the chromosomes from the cytoplasm. A similar process encloses sperm chromatin in egg cytoplasm following fertilization. A number of studies emphasizing the role of proteins have addressed the mechanism of nuclear envelope assembly, many utilizing cell-free systems derived from eggs or somatic cells (1-4). However, relatively little attention has been paid to the essential role(s) played by membrane lipids in this process.Male pronuclear or somatic nuclear envelope formation involves binding of nuclear membrane precursors to the chromatin surface followed by fusion to create a double membrane enclosing the chromatin (1, 5-7). We have previously reported that envelope formation in a cell-free system derived from sea urchin eggs requires the fusion of three egg membrane vesicle populations and remnants of the sperm nuclear envelope at the tip and base of the conical nucleus (8 -10).One of the egg vesicle populations (MV1) 3 is particularly unusual. It is a low density fraction highly enriched in the membrane lipid phosphatidylinositol (PtdIns) (9, 11). MV1 binds at the tip and base of the sperm nucleus and is required for nuclear envelope formation, which can be induced by addition of GTP or a bacterial PtdIns-specific phospholipase C (PI-PLC) (9, 12). The endogenous sea urchin PI-PLC activity probably resembles a typical eukaryotic enzyme whose substrate is PtdIns(4,5)P 2 . GTP-initiated envelope formation is inhibited by GTP␥S and by the PI 3-kinase inhibitors, wortmannin and LY294002 (12, 13). Initi...

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Section: Mv2 Inducers Envelope Formation Inhibitorsmentioning

confidence: 76%

mentioning

confidence: 67%

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Diacylglycerol Induces Fusion of Nuclear Envelope Membrane Precursor Vesicles

Barona

Byrne

Pettitt

et al. 2005

Journal of Biological Chemistry

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“…OAG promotes TRPC3 activity, but the mechanism of this action has not been elucidated (2,3,31) perhaps due to inconsistencies between the endogenous and overexpressed channels (32,33). This is further illustrated by our Ca 2ϩ entry measurements in non-transfected PC12 cells (Fig.…”

Section: Resultsmentioning

confidence: 85%

“…We propose that the increased affinity for plasma membrane lipids inhibits the membrane destabilization of TRPC3-containing vesicles by DAG. In support, DAG is a well characterized cone-shaped lipid that destabilizes membranes at synapses, thus increasing vesicle fusion (2,3). DAG increases the negative curvature of membranes (i.e.…”

Section: Discussionmentioning

confidence: 99%

TRP_2, a Lipid/Trafficking Domain That Mediates Diacylglycerol-induced Vesicle Fusion

Rossum

Oberdick

Rbaibi

et al. 2008

Journal of Biological Chemistry

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Protein and lipid signaling in membrane fusion: nuclear envelope assembly

Larijani

Poccia²

2007

Signal Transduction

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Membrane fusion is important in many cell processes including membrane trafficking, mitotic reconstitution of organelles, viral infection and fertilization. Several fusion events occur just prior and subsequent to fertilization in the sea urchin, including the sperm acrosomal reaction, fusion of sperm and egg plasma membranes, exocytosis of cortical granules, reassembly of the sperm nuclear envelope and fusion of the male and female pronuclear envelopes leading to the zygote nucleus of the one‐cell embryo. The study of male pronuclear membrane dynamics with cell‐free extracts of fertilized sea urchin eggs has revealed several novel features, in particular a structural role arising from altering phospholipids prior to nuclear membrane formation. Fusion of chromatin‐bound membrane vesicles in vitro can be triggered by either GTP hydrolysis or exogenous phosphatidyl inositol phospholipase C (PI‐PLC). Recent data strongly implicate a role for diacylglycerol in nuclear envelope formation as a structural destabilizing lipid in membrane fusion. Moreover, the endogenous enzyme, PI‐PLCγ, is >100‐fold enriched in a nuclear envelope precursor vesicle population (MV1) that is required for nuclear envelope assembly. NMR and mass spectrometry analyses show that MV1 contains high levels of phosphoinositides, including the substrate of PLCγ, compared to the other nuclear envelope precursor membranes. MV1 exists in eggs as vesicles in the cortex distinct from the endoplasmic reticulum which contributes most of the nuclear envelope membrane. PLCγ is activated by a tyrosine kinase in response to GTP hydrolysis at an early stage of nuclear envelope formation suggesting a role in initiation of fusion and revealing aspects of a signaling mechanism leading to fusion. The binding of MV1 to two poles of the sperm nucleus offers spatial as well as temporal control of the initiation phase.

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Diacylglycerol effects on phosphatidylinositol‐specific phospholipase C activity and vesicle fusion

Cited by 35 publications

References 21 publications

Diacylglycerol Induces Fusion of Nuclear Envelope Membrane Precursor Vesicles

Diacylglycerol Induces Fusion of Nuclear Envelope Membrane Precursor Vesicles

TRP_2, a Lipid/Trafficking Domain That Mediates Diacylglycerol-induced Vesicle Fusion

Protein and lipid signaling in membrane fusion: nuclear envelope assembly

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