Functional disparity between human PAWP and PLCζ in the generation of Ca2+ oscillations for oocyte activation

Mol Hum Reprod. 2015 Sep;21(9):702-10. doi: 10.1093/molehr/gav034. Epub 2015 Jun 26.

Abstract

Mammalian oocyte activation is mediated by cytosolic calcium (Ca(2+)) oscillations initiated upon delivery of a putative 'sperm factor' by the fertilizing sperm. Previous studies suggest the identity of this sperm factor as the testis-specific phospholipase C-zeta (PLCζ). Recently, a post-acrosomal sheath WW domain-binding protein (PAWP) has been proposed as an alternative sperm factor candidate, following a report that human PAWP protein and cRNA elicited Ca(2+) oscillations in mouse and human oocytes. Those Ca(2+) oscillations were inhibited by a PAWP-derived peptide corresponding to a functional PPGY binding motif. Herein, using a series of human PAWP expression constructs, we demonstrate that both human PAWP protein and cRNA are, in our experiments, unable to elicit Ca(2+) release following microinjection into mouse oocytes. Parallel experiments performed with human PLCζ elicited the characteristic Ca(2+) oscillations present at mammalian fertilization, which produced oocyte activation and embryo development. Furthermore, sperm-induced Ca(2+) oscillations were not inhibited by the PAWP-derived PPGY peptide following in vitro fertilization or intracytoplasmic sperm injection. Thus, the functional disparity with PLCζ leads us to conclude that human PAWP is neither sufficient nor necessary for the Ca(2+) oscillations that initiate mammalian oocyte activation at fertilization.

Keywords: PAWP; fertilization; oocyte activation; phospholipase C zeta; sperm factor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Signaling* / drug effects
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cells, Cultured
  • Female
  • Fertilization in Vitro
  • Gene Transfer Techniques
  • Humans
  • In Vitro Oocyte Maturation Techniques
  • Male
  • Mice
  • Microinjections
  • Oocytes / drug effects
  • Oocytes / enzymology*
  • Peptide Fragments / pharmacology
  • Phosphoinositide Phospholipase C / genetics
  • Phosphoinositide Phospholipase C / metabolism*
  • Seminal Plasma Proteins / genetics
  • Seminal Plasma Proteins / metabolism*
  • Sperm Injections, Intracytoplasmic
  • Sperm-Ovum Interactions
  • Spermatozoa / metabolism
  • Time Factors

Substances

  • Carrier Proteins
  • Peptide Fragments
  • Seminal Plasma Proteins
  • WBP2NL protein, human
  • PLCZ1 protein, human
  • Phosphoinositide Phospholipase C