Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.13/804302

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Title
Mammalian sperm contain a Ca²⁺-sensitive phospholipase C activity that can generate InsP₃ from PIP₂ associated with intracellular organelles
Author/Creator
Rice, Anne;  Parrington, John;  Jones, Keith T.;  Swann, Karl
Description
We have previously described a phospholipase C (PLC) activity in mammalian sperm cytosolic extracts. Here we have examined the Ca²⁺ dependency of the enzyme, whether there is enough in a single sperm to account for Ca²⁺ release at fertilization, and finally where in the egg is the phosphatidyl 4,5-bisphosphate, the substrate for the enzyme. As for all PLCs examined so far in vitro, we found that the boar sperm PLC activity was Ca²⁺ dependent. Specific activity increased when free Ca²⁺ levels were micromolar. However, even at nanomolar free Ca²⁺ concentration the boar sperm PLC activity was considerable, being two orders of magnitude greater than PLC activities in other tissues. We calculated that PLC activity of a single boar sperm in a mammalian egg is enough to generate 400 nM inositol 1,4,5-trisphosphate (InsP₃) in 1 min, which may be sufficient to account for the observed Ca²⁺ changes in an egg at fertilization. We fractionated sea urchin egg homogenate and examined the ability of boar sperm extract to generate InsP₃ from these fractions. The sperm PLC activity triggered InsP₃ production from a PIP₂-enriched nonmicrosomal egg compartment that contained yolk platelets. We propose that this sperm PLC activity, which is active at nanomolar Ca²⁺ levels and hydrolyzes PIP₂ from intracellular membranes, could be involved in the Ca²⁺ changes observed at fertilization.
Relation
Academic Press Vol. 228, Issue 1, p. 125-135
Publisher Link
http://dx.doi.org/10.1006/dbio.2000.9929
Date
2000
Publisher
Academic Press
Keyword(s)
phospholipase C;  sperm;  egg;  fertilization;  calcium;  phosphatidylinositol 4,5-bisphosphate.;  inositol 1,4,5-trisphosphate;;  sperm factor
Resource Type
journal article
Identifier
http://hdl.handle.net/1959.13/804302
Identifier
ISSN:0012-1606
Language
eng
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"Academic Press"
 
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