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Lipid raft on gametic cells as a functional domain for sperm–egg interaction coupled with signal transduction
Published online by Cambridge University Press: 16 July 2018
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It has been shown that lipid raft, a microdomain of plasma membrane, is a hot spot of signal transduction in somatic cells, because it contains several transducer proteins as well as various receptor molecules. The lipid raft is characterised by its low-density detergent-insoluble nature and by enrichment of glycosphingolipids (GSLs). We hypothesised that lipid raft was also on the gamete surface, and might function as a sperm–egg adhesion site as well as in signal transduction during fertilisation. To test this hypothesis, we have initiated studies using sea urchin gametes. Recently we have demonstrated the presence of the lipid raft in sperm of three sea urchin species as the first example in gametic cells (Ohta et al., 1999). Here we show several lines of evidence for the functional importance of the lipid raft in sperm–egg interaction as well as in subsequent signal transduction.
In sea urchin sperm, lipid rafts were able to be prepared as a low-density detergent-insoluble membrane (LD-DIM) fraction and were rich in GSLs including gangliosides and sulphatide, containing more than 50% of the total amount of GSL present in sperm. On the other hand, cholesterol and sphingomyelin were not so enriched, which contrasted with the LD-DIM from MDCK cells, where these lipids were reported to be abundant (Brown & Rose, 1992).
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- Copyright © Cambridge University Press 1999
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