Sperm-specific post-acrosomal WW-domain binding protein (PAWP) does not cause Ca2+ release in mouse oocytes

Michail Nomikos, Jessica R. Sanders, Maria Theodoridou, Junaid Kashir, Emily Matthews, George Nounesis, F. Anthony Lai, Karl Swann

Research output: Contribution to journalArticlepeer-review

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Maturemammalianoocytes undergoa prolongedseries of cytoplasmic calcium(Ca2+) oscillations at fertilizationthat are thecauseof oocyte activation. The Ca2+ oscillations in mammalian oocytes are driven via inositol 1,4,5-trisphosphate (IP3) generation. Microinjection of the sperm-derived phospholipase C-zeta (PLCζ), which generates IP3, causes the same pattern of Ca2+ oscillations as observed at mammalian fertilization and it is thought to be the physiological agent that triggers oocyte activation. However, another sperm-specific protein, 'post-acrosomal WW-domain binding protein' (PAWP), has also been reported to elicit activation when injected into mammalian oocytes, and to produce a Ca2+ increase in frog oocytes. Here we have investigated whether PAWP can induce fertilization-like Ca2+ oscillations in mouse oocytes. Recombinant mouse PAWP protein was found to be unable to hydrolyse phosphatidylinositol 4,5-bisphosphate in vitro and did not cause any detectable Ca2+ releasewhenmicroinjected intomouse oocytes.Microinjection with cRNA encoding either the untagged PAWP, or yellow fluorescent protein (YFP)-PAWP, or luciferase-PAWP fusion proteins all failed to trigger Ca2+ increases inmouse oocytes.The lack of response inmouse oocytes was despite PAWPbeing robustly expressed at similar or higher concentrations than PLCζ, which successfully initiated Ca2+ oscillations in every parallel control experiment. These data suggest that sperm-derived PAWP is not involved in triggering Ca2+ oscillations at fertilization in mammalian oocytes.

Original languageBritish English
Pages (from-to)938-947
Number of pages10
JournalMolecular Human Reproduction
Issue number10
StatePublished - 1 Oct 2014


  • Fertilization
  • Oocyte activation
  • PAWP
  • PLCζ
  • Sperm factor


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