Molecular Human Reproduction, Vol. 5, No. 11, 1027-1033,
November 1999
© 1999 European Society of Human Reproduction and Embryology
Molecular aspects of fertilization |
PI-PLC releases a 2540 kDa protein cluster from the hamster oolemma and affects the sperm penetration assay
Center for Recombinant Gamete Contraceptive Vaccinogens, University of Virginia, Charlottesville, VA 22908, USA
Abstract
The effects of phosphatidylinositol-specific phospholipase C (PI-PLC) on human spermhamster oocyte interaction were investigated to determine whether PI-PLC cleavable glycosylphosphatidyinositol (GPI)-anchored proteins are involved in spermegg binding and fusion. Two-dimensional electrophoresis was then utilized to visualize proteins released from hamster oocytes following PI-PLC treatment. For the binding and fusion assay, either spermatozoa or eggs were treated with 1 IU/ml PI-PLC for 30 min and washed prior to gamete co-incubation. Treatment of human spermatozoa with PI-PLC significantly (P
0.05) enhanced spermegg binding while having no effect on spermegg fusion. Treatment of zona-free hamster oocytes with PI-PLC blocked spermegg binding and fusion. In order to identify the oolemmal GPI-anchored proteins involved in fertilization, egg surface proteins were labelled with sulpho-NHS biotin and either mock treated or treated with PI-PLC. Egg protein extracts and egg supernatant proteins from each group were then analysed by two-dimensional gel electrophoresis followed by avidin blotting. Comparison of blots demonstrated that a predominant biotinylated 2540 kDa protein cluster (pI 56) apparent in the mock treated egg extract blot was absent in the PI-PLC treated egg extract blot. A protein cluster of identical molecular weight and isoelectric point as the predominant 2540 kDa protein cluster was observed in the PI-PLC supernatant blot while no proteins could be seen in the control supernatant blot. These results demonstrate that treatment of hamster oocytes with PI-PLC inhibits spermegg interaction and releases a 2540 kDa protein cluster (pI 56) from the oolemma. It is likely that this released protein cluster represents an oolemmal GPI-linked surface protein(s) which is involved in human spermhamster egg interaction.
GPI-anchored/spermegg interaction/two-dimensional electrophoresis
Notes