Summary
Shiga toxin (Stx)-producing Escherichia coli (STEC) cause an enteric illness that results in a spectrum of outcomes ranging from
asymptomatic carriage to uncomplicated diarrhea, bloody diarrhea, and the postdiarrheal
haemolytic uremic syndrome (HUS), which leads to renal and other organ microvascular
thrombosis. Binding of Stx to the glycosphingolipid (GSL) globotriaosylceramide (Gb3Cer/CD77)
on endothelial cells followed by receptor-mediated endocytosis is the linchpin in
STEC-mediated disease. Only GSLs that associate strongly with lipid rafts appear to
carry Stxs retrogradely from the plasma membrane through the Golgi apparatus to the
endoplasmic reticulum where they are translocated to the cytosol and exert their toxic
function. Thus, the biophysical features of the lipid moiety of GSL receptors may
influence its incorporation into certain membrane domains and thereby affect toxin
destination. Consequently, a detailed structural analysis of Stx-binding GSLs is required
to illuminate the molecular causes that may underlie the different Stx susceptibilities
of endothelial cells derived from various vascular beds. Solid phase overlay binding
assays of thin-layer chromatography (TLC)-separated GSL preparations employing specific
antibodies and/or Stxs in conjunction with anti-Stx-antibodies are commonly used for
the identification of Stx-binding GSLs. Such GSL-profiling combined with matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) represents
a convenient strategy to structurally characterize Stx-receptors from any biological
sources such as primary cells, cell lines, or organs. This approach may be helpful
to gain insights into Stx-induced impairment of target cells that is suggested to
originate at least partly from the structural heterogeneity of the cellular ligands
of Stxs.
Keywords
STEC - Gb3Cer - endothelial cells - TLC overlay assay - MALDITOF-MS