Shiga toxins, glycosphingolipid diversity, and endothelial cell injury

Abstract

SummaryShiga 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.

Shiga toxin glycosphingolipid receptors in microvascular and macrovascular endothelial cells: differential association with membrane lipid raft microdomains

“…They are embedded with the ceramide moiety in the outer leaflet of the plasma membrane of animal cells, where they are clustered in a more ordered state within the generally disordered milieu of the membrane. The localization of GSLs in the exofacial leafl et of the plasma membrane makes them excellent candidates as recognition structures in cell-cell interactions ( 16 ) and as receptors for numerous pathogens, such as viruses ( 17,18 ) and bacteria ( 19,20 ), as well as for bacterial toxins, including Shiga toxins (Stxs) ( 21,22 ). Much effort is currently spent employing (glyco)sphingolipidomics (23)(24)(25)(26) by use of various mass spectrometry technologies ( 15,(27)(28)(29)(30)(31) to better understanding their nature and functional role ( 32 ).…”

Evaluation of an Immuno-Chromatographic Detection System for Shiga Toxins and the E. coli O157 Antigen

“…The toxin subunit B is responsible for binding the toxin to GB3 or GB4 receptors on the eukaryotic cells. Stx1 and Stx2 are immunologically not cross-reactive and show themselves to be 55% different in their amino acid sequences (Muthing et al 2009). A number of genetic variants were identified within the Stx1 and the Stx2 toxin families (Burk et al 2003;Leung et al 2003;Muthing et al 2009).…”

“…Stx1 and Stx2 are immunologically not cross-reactive and show themselves to be 55% different in their amino acid sequences (Muthing et al 2009). A number of genetic variants were identified within the Stx1 and the Stx2 toxin families (Burk et al 2003;Leung et al 2003;Muthing et al 2009). The variants differ in the amino-acid substitutions in their StxA and StxB subunits, which can have an influence on their toxicity and receptor-binding specificity (Muthing et al 2009).…”

“…A number of genetic variants were identified within the Stx1 and the Stx2 toxin families (Burk et al 2003;Leung et al 2003;Muthing et al 2009). The variants differ in the amino-acid substitutions in their StxA and StxB subunits, which can have an influence on their toxicity and receptor-binding specificity (Muthing et al 2009). The Stx1 group has been divided into the subtypes Stx1, Stx1a, Stx1c and Stx1d (Burk et al 2003) (Figure 1).…”

Glycosphingolipids in HIV/AIDS: The Potential Therapeutic Application

“…It is of interest to note that HIV infected patients are more prone to haemolytic uremic syndrome (HUS) (Turner et al, 1997). HUS is characterised by thrombotic microangiopathy of the renal glomeruli mediated by verotoxin/Gb 3 binding (Muthing et al, 2009). It is thus interesting that transgenic mice, in which the HIV genome has been incorporated into the germ line, show renal Gb 3 synthesis is selectively upregulated to induce renal disease (Liu et al, 1999) …”