The glycan core of GPI-anchored proteins modulates aerolysin binding but is not sufficient: the polypeptide moiety is required for the toxin-receptor interaction.
Sensitivity of mammalian cells to the bacterial toxin aerolysin is due to the presence at their surface of glycosylphosphatidyl inositol (GPI)-anchored proteins which act as receptors. Using a panel of mutants that are affected in the GPI biosynthetic pathway and Trypanosoma brucei variant surface glycoproteins, we show that addition of an ethanolamine phosphate residue on the first mannose of the glycan core does not affect binding. In contrast, the addition of a side chain of up to four galactose residues at position 3 of this same mannose leads to an increase in binding. However, protein free GPIs, which accumulate in mutant cells deficient in the transamidase that transfers the protein to the pre-formed GPI-anchor, were unable to bind the toxin indicating a requirement for the polypeptide moiety, the nature and size of which seem of little importance although two exceptions have been identified.
Abrami
Laurence
L
Department of Genetics and Microbiology, University of Geneva, 1 rue Michel Servet, 1211 4, Geneva, Switzerland.
Velluz
Marie Claire
MC
Hong
Yeongjin
Y
Ohishi
Kazuhito
K
Mehlert
Angela
A
Ferguson
Michael
M
Kinoshita
Taroh
T
Gisou van der Goot
F
F
D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D006023:Glycoproteins / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006367:HeLa Cells; D006460:Hemolysin Proteins / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D037102:Lectins; D008358:Mannose / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000378:metabolism
D001427:Bacterial Toxins; D006023:Glycoproteins; D017261:Glycosylphosphatidylinositols; D006460:Hemolysin Proteins; D037102:Lectins; D052899:Pore Forming Cytotoxic Proteins; D011956:Receptors, Cell Surface; D014643:Variant Surface Glycoproteins, Trypanosoma; C032676:aerolysin; D008358:Mannose