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J Cell Sci. 2017 Jan 15;130(2):444-452. doi: 10.1242/jcs.193771. Epub 2016 Dec 7.

Vesicular PtdIns(3,4,5)P3 and Rab7 are key effectors of sea urchin zygote nuclear membrane fusion.

Author information

1
Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Instituto (UPV/EHU, CSIC), University of the Basque Country, Areatza Hiribidea, 47, 48620 Plentzia, Spain.
2
Biofísika Instituto (UPV/EHU, CSIC) and Departamento de Bioquímica, University of the Basque Country, Barrio Sarriena s/n, Leioa 48940, Spain.
3
Cell Biophysics Laboratory, Research Centre for Experimental Marine Biology and Biotechnology (PiE), Biofisika Instituto (UPV/EHU,CSIC) and, University of the Basque Country, Leioa 48940, Spain.
4
The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London NW7 1AA, UK.
5
Department of Biology, Amherst College, Amherst, MA 01002, USA.
6
Cell Biophysics Laboratory, Research Centre for Experimental Marine Biology and Biotechnology (PiE), Biofisika Instituto (UPV/EHU,CSIC) and, University of the Basque Country, Leioa 48940, Spain banafshe.larijani@ikerbasque.org.

Abstract

Regulation of nuclear envelope dynamics is an important example of the universal phenomena of membrane fusion. The signalling molecules involved in nuclear membrane fusion might also be conserved during the formation of both pronuclear and zygote nuclear envelopes in the fertilised egg. Here, we determine that class-I phosphoinositide 3-kinases (PI3Ks) are needed for in vitro nuclear envelope formation. We show that, in vivo, PtdIns(3,4,5)P3 is transiently located in vesicles around the male pronucleus at the time of nuclear envelope formation, and around male and female pronuclei before membrane fusion. We illustrate that class-I PI3K activity is also necessary for fusion of the female and male pronuclear membranes. We demonstrate, using coincidence amplified Förster resonance energy transfer (FRET) monitored using fluorescence lifetime imaging microscopy (FLIM), a protein-lipid interaction of Rab7 GTPase and PtdIns(3,4,5)P3 that occurs during pronuclear membrane fusion to create the zygote nuclear envelope. We present a working model, which includes several molecular steps in the pathways controlling fusion of nuclear envelope membranes.

KEYWORDS:

FRET–FLIM; Membrane fusion; Nuclear envelope; Phosphoinositide 3-kinase; Phosphoinositides; Rab GTPases; Src kinase; Zygote formation

PMID:
27927752
DOI:
10.1242/jcs.193771
[Indexed for MEDLINE]
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