Mammalian fertilization: from sperm factor to phospholipase Czeta.
In mammalian eggs, the fertilizing sperm evokes intracellular Ca2+ ([Ca2+]i) oscillations that are essential for initiation of egg activation and embryonic development. Although the exact mechanism leading to initiation of [Ca2+]i oscillations still remains unclear, accumulating studies suggest that a presently unknown substance, termed sperm factor (SF), is delivered from the fertilizing sperm into the ooplasm and triggers [Ca2+]i oscillations. Based on findings showing that production of inositol 1,4,5-trisphosphate (IP3) underlies the generation of [Ca2+]i oscillations, it has been suggested that SF functions either as a phospholipase C (PLC), an enzyme that catalyzes the generation of IP3, or as an activator of a PLC(s) pre-existing in the egg. This review discusses the role of SF as the molecule responsible for the production of IP3 and the initiator of [Ca2+]i oscillations in mammalian fertilization, with particular emphasis on the possible involvement of egg- and sperm-derived PLCs, including PLCzeta, a novel sperm specific PLC.
Kurokawa
Manabu
M
Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01373, USA.
Sato
Ken-ichi
K
Fissore
Rafael A
RA
D000818:Animals; D005260:Female; D005306:Fertilization / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis / Q000378:metabolism; D008297:Male; D010063:Ovum / Q000201:enzymology; D054801:Phosphoinositide Phospholipase C; D013094:Spermatozoa / Q000201:enzymology / Q000378:metabolism*; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism*
D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; C499235:PLCZ1 protein, human; D054801:Phosphoinositide Phospholipase C; C499234:Plcz1 protein, mouse