Human PLCζ exhibits superior fertilization potency over mouse PLCζ in triggering the Ca(2+) oscillations required for mammalian oocyte activation.
A sperm-specific phospholipase C-zeta (PLCζ) is believed to play an essential role in oocyte activation during mammalian fertilization. Sperm PLCζ has been shown to trigger a prolonged series of repetitive Ca(2+) transients or oscillations in oocytes that precede activation. This remarkable intracellular Ca(2+) signalling phenomenon is a distinctive characteristic observed during in vitro fertilization by sperm. Previous studies have notably observed an apparent differential ability of PLCζ from disparate mammalian species to trigger Ca(2+) oscillations in mouse oocytes. However, the molecular basis and confirmation of the apparent PLCζ species difference in activity remains to be provided. In the present study, we provide direct evidence for the superior effectiveness of human PLCζ relative to mouse PLCζ in generating Ca(2+) oscillations in mouse oocytes. In addition, we have designed and constructed a series of human/mouse PLCζ chimeras to enable study of the potential role of discrete PLCζ domains in conferring the enhanced Ca(2+) signalling potency of human PLCζ. Functional analysis of these human/mouse PLCζ domain chimeras suggests a novel role of the EF-hand domain in the species-specific differences in PLCζ activity. Our empirical observations are compatible with a basic mathematical model for the Ca(2+) dependence of generating cytoplasmic Ca(2+) oscillations in mammalian oocytes by sperm PLCζ.
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK mixosn@yahoo.com lait@cf.ac.uk.
Michail
M
Nomikos
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK National Center for Scientific Research 'Demokritos', Aghia Paraskevi 15310, Greece.
Maria
M
Theodoridou
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
Khalil
K
Elgmati
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
Dimitris
D
Parthimos
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
Brian L
BL
Calver
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
Luke
L
Buntwal
National Center for Scientific Research 'Demokritos', Aghia Paraskevi 15310, Greece.
George
G
Nounesis
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK.
Karl
K
Swann
Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK mixosn@yahoo.com lait@cf.ac.uk.
F Anthony
FA
Lai
D000328:Adult; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005260:Female; D005307:Fertilization in Vitro; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D050506:Mutant Chimeric Proteins / Q000235:genetics / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D054801:Phosphoinositide Phospholipase C / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013045:Species Specificity; D013084:Sperm-Ovum Interactions / Q000235:genetics*; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*
D050506:Mutant Chimeric Proteins; D008156:Luciferases; C499235:PLCZ1 protein, human; D054801:Phosphoinositide Phospholipase C; C499234:Plcz1 protein, mouse; D002118:Calcium
PLCzeta; fertilization; male infertility; oocyte activation; phospholipase C; sperm