|
|||||
|
|
Lipophosphoglycan expression and virulence in ricin-resistant variants of Leishmania major |
|
| Authors: | Martin Elhay Michelle Kelleher Antony Bacic Malcolm J. McConville Douglas L. Tolson Terry W. Pearson Emanuela Handman |
| Affiliation: | a The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia b Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville, Victoria, Australia c Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada d Department of Biochemistry, The University of Dundee, Dundee, U.K. |
| Abstract: | Lipophosphoglycan (LPG) of Leishmania is a polymorphic molecule comprising an alkylglycerol anchor, a conserved oligosaccharide core and a species-specific polymer of oligosaccharide repeats joined by phosphodiester bonds. This molecule, together with the membrane polypeptide gp63, has been implicated as a parasite receptor for host macrophages. To examine the role of LPG in parasite infectivity glycosylation variants of Leishmania major were generated by chemical mutagenesis of a virulent cloned line V121 and variants with modified LPG selected using the galactose-specific lectin Ricinus communis II (RCA II). Twenty RCA II-resistant primary clones were generated. Analysis of LPG profile by immunoblotting using LPG-specific monoclonal and polyclonal antibodies revealed that some of the clones were LPG-deficient. Three clones that did not bind any LPG-specific antibodies but expressed normal levels of the Mr 63 000 glycoprotein (gp63), a second parasite receptor for host, were chosen for detailed studies. All three clones expressed, at least to some extent, a surface molecule which could be labeled by mild periodate oxidation and sodium borotritide and behaved like LPG by hydrophobic interaction chromatography. All clones also bound a well-characterized monoclonal antibody L157 directed to the core oligosaccharide of LPG, but did not bind another monoclonal antibody, CA7AE, to an epitope on a repeating unit shared by Leishmania donovani and L. major LPG. A third monoclonal antibody, 5E6, recognizing LPG on the surface of wild-type V121 promastigotes bound only to RCA II-resistant clone 3A2-C3 and was restricted to an internal structure. The LPG molecule that this clone expressed was a form of LPG by its chromatographic behavior and by its monosaccharide and alkylglycerol composition. Clone 3A2-C3 was the only one to infect mice in vivo and survive in macrophages in vitro, albeit at a much reduced rate compared to wild-type V121 promastigotes. The data suggest that some form of LPG may be necessary to ensure parasite infectivity. |
| Keywords: | Lipophosphoglycan Glycolipid Glycosylation variants Ricinus communis agglutinin II Leishmania major |
| 本文献已被 ScienceDirect 等数据库收录！ | |