title: Divergent effect of mammalian PLCζ in generating Ca²⁺ oscillations in somatic cells compared with eggs.
abstract: Sperm PLCζ (phospholipase Cζ) is a distinct phosphoinositide-specific PLC isoform that is proposed to be the physiological trigger of egg activation and embryo development at mammalian fertilization. Recombinant PLCζ has the ability to trigger Ca²⁺ oscillations when expressed in eggs, but it is not known how PLCζ activity is regulated in sperm or eggs. In the present study, we have transfected CHO (Chinese-hamster ovary) cells with PLCζ fused with either YFP (yellow fluorescent protein) or luciferase and found that PLCζ-transfected cells did not display cytoplasmic Ca²⁺ oscillations any differently from control cells. PLCζ expression was not associated with changes in CHO cell resting Ca²⁺ levels, nor with a significantly changed Ca²⁺ response to extracellular ATP compared with control cells transfected with either YFP alone, a catalytically inactive PLCζ or luciferase alone. Sperm extracts containing PLCζ also failed to cause Ca²⁺ oscillations in CHO cells. Despite these findings, PLCζ-transfected CHO cell extracts exhibited high recombinant protein expression and PLC activity. Furthermore, either PLCζ-transfected CHO cells or derived cell extracts could specifically cause cytoplasmic Ca²⁺ oscillations when microinjected into mouse eggs. These data suggest that PLCζ-mediated Ca²⁺ oscillations may require specific factors that are only present within the egg cytoplasm or be inhibited by factors present only in somatic cell lines.
authors.affiliation: Department of Obstetrics and Gynaecology, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK.
authors.forename: Sally V
authors.initials: SV
authors.lastname: Phillips
authors.forename: Yuansong
authors.initials: Y
authors.lastname: Yu
authors.forename: Andreas
authors.initials: A
authors.lastname: Rossbach
authors.forename: Michail
authors.initials: M
authors.lastname: Nomikos
authors.forename: Vyronia
authors.initials: V
authors.lastname: Vassilakopoulou
authors.forename: Evangelia
authors.initials: E
authors.lastname: Livaniou
authors.forename: Bevan
authors.initials: B
authors.lastname: Cumbes
authors.forename: F Anthony
authors.initials: FA
authors.lastname: Lai
authors.forename: Christopher H
authors.initials: CH
authors.lastname: George
authors.forename: Karl
authors.initials: K
authors.lastname: Swann
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D006224:Cricetinae; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008322:Mammals / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D054801:Phosphoinositide Phospholipase C / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D001426:Bacterial Proteins; D008164:Luminescent Proteins; D011994:Recombinant Proteins; C054562:yellow fluorescent protein, Bacteria; D000255:Adenosine Triphosphate; D054801:Phosphoinositide Phospholipase C; D002118:Calcium