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PAWP, a Sperm-specific WW Domain-binding Protein, Promotes Meiotic Resumption and Pronuclear Development during Fertilization

2007; Elsevier BV; Volume: 282; Issue: 16 Linguagem: Inglês

10.1074/jbc.m609132200

1083-351X

Alexander T.H. Wu, Peter Šutovský, Gaurishankar Manandhar, Wei Xu, Mika Katayama, Billy N. Day, Kwang‐Wook Park, Young‐Joo Yi, Yan Wei Xi, Randall S. Prather, Richard Oko,

Animal Genetics and Reproduction

We report a novel alkaline extractable protein of the sperm head that exclusively resides in the post-acrosomal sheath region of the perinuclear theca (PT) and is expressed and assembled in elongating spermatids. It is a protein that shares sequence homology to the N-terminal half of WW domain-binding protein 2, while the C-terminal half is unique and rich in proline. A functional PPXY consensus binding site for group-I WW domain-containing proteins, and numerous unique repeating motifs, YGXPPXG, are identified in the proline-rich region. Considering these molecular characteristics, we designated this protein PAWP for postacrosomal sheath WW domain-binding protein. Microinjection of recombinant PAWP or alkaline PT extract into metaphase II-arrested porcine, bovine, macaque, and Xenopus oocytes induced a high rate of pronuclear formation, which was prevented by co-injection of a competitive PPXY motif containing peptide derived from PAWP but not by co-injection of the point-mutated peptide. Intracytoplasmic sperm injection (ICSI) of porcine oocytes combined with co-injection of the competitive PPXY peptide or an anti-recombinant PAWP antiserum prevented pronuclear formation and arrested fertilization. Conversely, co-injection of the modified PPXY peptide, when the tyrosine residue of PPXY was either phosphorylated or substituted with phenylalanine, did not prevent ICSI-induced fertilization. This study uncovers a group I WW domain module signal transduction event within the fertilized egg that appears compulsory for meiotic resumption and pronuclear development during egg activation and provides compelling evidence that a PPXY motif of sperm-contributed PAWP can trigger these events.