GLYCOSYLPHOSPHATIDYLINOSITOL ANCHORS OF MEMBRANE-GLYCOPROTEINS ARE BINDING DETERMINANTS FOR THE CHANNEL-FORMING TOXIN AEROLYSIN

Cells that are sensitive to the channel-forming toxin aerolysin contai n surface glycoproteins that bind the toxin with high affinity, Here w e show that a common feature of aerolysin receptors is the presence of a glycosylphosphatidylinositol anchor, and we present evidence that t he anchor itself is an essential part of the toxin binding determinant , The glycosylphosphatidylinositol (GPI)-anchored T-lymphocyte protein Thy-1 is an example of a protein that acts as an aerolysin recep tor, This protein retained its ability to bind aerolysin when it was expre ssed in Chinese hamster ovary cells, but could not bind the toxin when expressed in Escherichia coli, where the GPI anchor is absent, An unr elated GPI-anchored protein, the variant surface glycoprotein of trypa nosomes, was shown to bind aerolysin with similar affinity to Thy-1, a nd this binding ability was significantly reduced when the anchor was removed chemically, Cathepsin D, a protein with no affinity for aeroly sin, was converted to an aerolysin binding form when it was expressed as a GPI-anchored hybrid in COS cells, Not all GPI-anchored proteins b ind aerolysin, In some cases this may be due to differences in the str ucture of the anchor itself. Thus the GPI-anchored proteins procyclin of Trypanosoma congolense and gp63 of Leishmania major did not bind ae rolysin, but when gp63 was expressed with a mammalian GPI anchor in Ch inese hamster ovary cells, it bound the toxin.