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Imaging of HIV-1 Envelope-induced Virological Synapse and Signaling on Synthetic Lipid Bilayers
Published on: March 8, 2012
Interaction of human immunodeficiency virus type 1 envelope glycoprotein gp120 with a galactoglycerolipid associated
A Brogi1, R Presentini, D Solazzo
1Istituto Biologia Generale, Università Siena, Italy.
Insights
Human sperm express a glycolipid similar to galactosylceramide, which binds gp120, the HIV envelope protein. This finding suggests sperm glycolipids may act as HIV receptors, potentially impacting transmission.
Area of Science:
- Reproductive Biology
- Virology
- Glycobiology
Background:
- Human spermatozoa express surface molecules involved in fertilization and pathogen interaction.
- Galactosylceramide is a known receptor for certain viruses on non-sperm cells.
- The role of specific sperm surface glycolipids in HIV transmission is not fully understood.
Purpose of the Study:
- To investigate the presence and nature of a galactosylceramide-like molecule on human sperm.
- To determine if this molecule binds gp120, the outer envelope protein of HIV.
- To explore the potential role of this sperm glycolipid as an HIV receptor.
Main Methods:
- Indirect immunofluorescence for localization of the molecule on sperm.
- Immuno-thin-layer chromatography for glycolipid identification.
- Enzyme-linked immunosorbent assay (ELISA) for binding specificity.
- Competition assays to assess binding site identity.
Main Results:
- A molecule recognized by anti-galactosyl ceramide antibodies (MAb O1) is localized on the middle piece of human sperm.
- The molecule is a glycolipid related to, but not identical to, galactosylceramide.
- This sperm glycolipid binds gp120, with evidence suggesting a shared binding site with antibodies.
- Preliminary analysis suggests the glycolipid is a galactosylalkylacylglycerolipid (GalAAG), a form of seminolipid.
Conclusions:
- Human sperm express a glycolipid structurally similar to known HIV receptors.
- This sperm glycolipid can bind gp120, suggesting it may function as an HIV receptor.
- The findings indicate a potential mechanism for HIV transmission via sperm.
Abstract:
The expression of a molecule recognized by anti-galactosyl ceramide antibodies (MAb) O1 on the surface membrane of human spermatozoa was investigated by biochemical and immunochemical methods. Indirect immunofluorescence shows that this molecule is preferentially localized on the middle piece of the sperm tail. Immuno-thin-layer chromatography has identified it as a glycolipid related but not identical to galactosylceramide. Consistent with a structure similar to galactosylceramide, the sperm glycolipid is capable of binding gp120. An improved ELISA has been utilized to demonstrate the specificity of binding of the antibodies and gp120 to the isolated lipid fraction. Identity of the binding site of the two ligands to the glycolipid is suggested by competition assays. On the basis of preliminary biochemical analysis this glycolipid was tentatively classified as a galactosylalkylacylglycerolipid (GalAAG), the nonsulfated form of the seminolipid, a glycolipid known to be present in the testis and germ cells of mammals. These data indicate that human sperm express a glycolipid similar in structure to the receptor for HIV described on the CD4- neural and colonic epithelial cell lines, and moreover suggest that this glycolipid could also function as HIV receptor and possibly be implicated in its transmission.
