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PLCζ causes Ca2+ oscillations in mouse eggs by targeting intracellular and not plasma membrane PI(4,5)P2

Yu, Yuansong, Nomikos, Michail, Theodoridou, Maria, Nounesis, George, Lai, Francis Anthony and Swann, Karl 2012. PLCζ causes Ca2+ oscillations in mouse eggs by targeting intracellular and not plasma membrane PI(4,5)P2. Molecular Biology of the Cell 23 (2) , pp. 371-380. 10.1091/mbc.E11-08-0687

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Abstract

Sperm-specific phospholipase C ζ (PLCζ) activates embryo development by triggering intracellular Ca2+ oscillations in mammalian eggs indistinguishable from those at fertilization. Somatic PLC isozymes generate inositol 1,4,5-trisphophate–mediated Ca2+ release by hydrolyzing phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) in the plasma membrane. Here we examine the subcellular source of PI(4,5)P2 targeted by sperm PLCζ in mouse eggs. By monitoring egg plasma membrane PI(4,5)P2 with a green fluorescent protein–tagged PH domain, we show that PLCζ effects minimal loss of PI(4,5)P2 from the oolemma in contrast to control PLCδ1, despite the much higher potency of PLCζ in eliciting Ca2+ oscillations. Specific depletion of this PI(4,5)P2 pool by plasma membrane targeting of an inositol polyphosphate-5-phosphatase (Inp54p) blocked PLCδ1-mediated Ca2+ oscillations but not those stimulated by PLCζ or sperm. Immunolocalization of PI(4,5)P2, PLCζ, and catalytically inactive PLCζ (ciPLCζ) revealed their colocalization to distinct vesicular structures inside the egg cortex. These vesicles displayed decreased PI(4,5)P2 after PLCζ injection. Targeted depletion of vesicular PI(4,5)P2 by expression of ciPLCζ-fused Inp54p inhibited the Ca2+ oscillations triggered by PLCζ or sperm but failed to affect those mediated by PLCδ1. In contrast to somatic PLCs, our data indicate that sperm PLCζ induces Ca2+ mobilization by hydrolyzing internal PI(4,5)P2 stores, suggesting that the mechanism of mammalian fertilization comprises a novel phosphoinositide signaling pathway.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Subjects: Q Science > QH Natural history > QH426 Genetics
R Medicine > R Medicine (General)
Additional Information: Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/1059-1524/ (accessed 24/02/2014)
Publisher: American Society for Cell Biology
ISSN: 1059-1524
Date of First Compliant Deposit: 30 March 2016
Last Modified: 02 May 2019 11:37
URI: http://orca-mwe.cf.ac.uk/id/eprint/25605

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