Mice infected with Schistosoma mansoni generate antibodies to LacdiNAc (GalNAc beta 1-->4GlcNAc) determinants

Schistosoma mansoni is a parasitic trematode infecting humans and animals. We reported previously that adult S. mansoni synthesizes complex type biantennary N-glycans bearing the terminal sequence GalNAc beta 1-->4GlcNAc-R (lacdiNAc or LDN). We now report that mice infected with S. mansoni generate antibodies to LDN, as assessed by ELISA using a synthetic neoglycoconjugate containing LDN sequences. Sera of infected mice, but not uninfected mice, contained primarily IgM and low levels of IgG toward LDN. Interestingly, these antibodies also recognize bovine milk glycoproteins, which are known to express LDN sequences. The anti-LDN in sera of infected mice were affinity purified on immobilized bovine milk glycoproteins and shown to specifically bind LDN. An IgM monoclonal antibody (SMLDN1.1) was derived from the spleens of S. mansoni infected mice and shown to specifically bind LDN determinants. Immunoblots with affinity purified anti-LDN and SMLDN1.1 demonstrate that LDN sequences occur primarily on N-glycans of numerous glycoproteins of adult S. mansoni. LDN sequences are also expressed in many glycoproteins from S. japonicum and S. haematobium. The availability of antibody to LDN determinants should aid in defining the roles of these glycans in helminth and vertebrate biology.

Failure to Cleave Sterol Regulatory Element-binding Proteins (SREBPs) Causes Cholesterol Auxotrophy in Chinese Hamster Ovary Cells with Genetic Absence of SREBP Cleavage-activating Protein

We describe a line of mutant Chinese hamster ovary cells, designated SRD-13A, that cannot cleave sterol regulatory element-binding proteins (SREBPs) at site 1, due to mutations in the gene encoding SREBP cleavage-activating protein (SCAP). The SRD-13A cells were obtained by two rounds of gamma-irradiation followed first by selection for a deficiency of low density lipoprotein receptors and second for cholesterol auxotrophy. In the SRD-13A cells, the only detectable SCAP allele encodes a truncated nonfunctional protein. In the absence of SCAP, the site 1 protease fails to cleave SREBPs, and their transcriptionally active NH(2)-terminal fragments cannot enter the nucleus. As a result, the cells manifest a marked reduction in the synthesis of cholesterol and its uptake from low density lipoproteins. The SRD-13A cells grow only when cholesterol is added to the culture medium. SREBP cleavage is restored and the cholesterol requirement is abolished when SRD-13A cells are transfected with expression vectors encoding SCAP. These results provide formal proof that SCAP is essential for the cleavage of SREBPs at site 1.

Schistosoma mansoni: characterization of an alpha 1-3 fucosyltransferase in adult parasites

We report that extracts of Schistosoma mansoni contain a GDPFuc:Gal beta 1-4GlcNAc (Fuc to GlcNAc) alpha 1-3 fucosyltransferase (alpha 1,3 FT) capable of synthesizing the antigenic determinant known as Lewis x (Le(x), Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-R). When the acceptor lacto-N-neotetraose (LNnT, Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc) was incubated with extracts of S. mansoni in the presence of GDPFuc and Mn2+, Fuc was transferred to generate the pentasaccharide lacto-N-fucopentaose III (LNFPIII, Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-3Gal Beta 1-4Glc). The enzyme did not transfer efficiently to the isomeric oligosaccharide lacto-N-tetraose (LNT, Gal beta 1-3GlcNAc beta 1-3Gal beta 1-4Glc). The activity of the schistosome alpha 1,3 FT toward LNnT was dependent upon time, protein and GDPFuc. Interestingly, the schistosome alpha 1,3 FT was also able to transfer Fuc to a sialic acid-containing trisaccharide NeuAc alpha 2-3 Gal beta 1-4 GlcNAc to produce the tetrasaccharide sialyl Lewis x (2,3 sLe(x), NeuAc alpha 2-3 Gal beta 1-4[Fuc 1-3]GlcNAc), although the rate of reaction with the sialylated acceptor was <5% of the rate obtained toward nonsialylated acceptor. The schistosome alpha 1,3 FT was relatively resistant to inhibition by N-ethylmaleimide. The enzymatic properties of the schistosome alpha 1,3 FT resemble those of the human myeloid fucosyltransferase FTIV and not those of other known human fucosyltransferase.