Phospholipase Cζ (PLCζ) versus postacrosomal sheath WW domain-binding protein (PAWP): Which molecule will survive as a sperm factor?

Michiko Nakai,Naomi Kashiwazaki,Atsuko Kageyama,Ayumi Suyama,Junya Ito,Yasuko Tobari

doi:10.1111/asj.13345

Abstract

During mammalian fertilization, sperm is fused with the oocyte's membrane, triggering the resumption of meiosis from the metaphase II arrest, the extrusion of the second polar body, and the exocytosis of cortical granules; these events are collectively called 'oocyte activation.' In all species studied to date, the transient rise in the cytosolic level of calcium (in particular, the repeated calcium increases called 'calcium oscillations' in mammals) is required for these events. Researchers have focused on identifying the factor(s) that can induce calcium oscillations during fertilization. Sperm‐specific phospholipase C, i.e., PLC zeta (PLCζ), is a strong candidate of the factor(s), and several research groups using different species obtained evidence that PLCζ is a sperm factor that can induce calcium oscillations during fertilization. However, postacrosomal sheath Tryptophan‐Tryptophan (WW)—domain‐binding protein (PAWP) was recently shown to have a pivotal role in inducing calcium oscillations in some species. In this review, we focus on PLCζ and PAWP as sperm factors, and we discuss this controversy: Which of these two molecules survives as a sperm factor?

Highlights

The point mutation of Asp210 to arginine in the X catalytic domain of phospholipase Cζ (PLCζ) caused the loss of calcium oscillation-inducing activity (Kuroda et al, 2006)
Calcium oscillations did not terminate at the time point of PN formation in mouse oocytes injected with pig PLCζ cRNA (Yoneda & Watanabe, 2015)
The authors showed that the sperm-induced calcium oscillations can be blocked by a co-injection of a competitive PY peptide. It suggests that both sperm-derived postacrosomal sheath Tryptophan-Tryptophan (WW)—domain-binding protein (PAWP) and an oocyte-derived group-I WW domain (WWI domain)-containing protein, such as “Yes-Associated Protein (YAP)”, “neural precursor cell expressed developmentally down-regulated protein (NEDD4)”, and “dystrophin”, are essential for successful fertilization via calcium oscillations

Summary

Introduction

Saunders et al (2002) proposed that phospholipase Cζ (PLCζ) might be the sperm-borne oocyte-activating factor that can induce calcium oscillations. TA B L E 1 Mammalian species studied for induction of oocyte activation by PLCζ or PAWP

Results

Conclusion