globotriaosylceramide and Kidney-Neoplasms

Shiga toxin is a bacterial toxin consisting of A and B subunits. Generally, the essential cytotoxicity of the toxin is thought to be mediated by the A subunit, which possesses RNA cleavage activity and thus induces protein synthesis inhibition. We previously reported, however, that the binding of the Shiga toxin 1-B subunit to globotriaosyl ceramide, a functional receptor for Shiga toxin, induces intracellular signals in a manner that is dependent on glycolipid-enriched membrane domains, or lipid rafts. Although the precise role of this signaling mechanism is not known, here we report that Shiga-toxin-mediated intracellular signals induce cytoskeleton remodeling in ACHN cells derived from renal tubular epithelial carcinoma. Using confocal laser scanning microscopy, we observed that Shiga toxin 1-B treatment induces morphological changes in ACHN cells in a time-dependent manner. In addition, the morphological changes were accompanied by the redistribution of a number of proteins, including actin, ezrin, CD44, vimentin, cytokeratin, paxillin, FAK, and alpha- and gamma-tubulins, all of which are involved in cytoskeletal organization. The transient phosphorylation of ezrin and paxillin was also observed during the course of protein redistribution. Experiments using inhibitors for a variety of kinases suggested the involvement of lipid rafts, Src family protein kinase, PI 3-kinase, and RHO-associated kinase in Shiga toxin 1-B-induced ezrin phosphorylation. Shiga toxin 1-B-induced cytoskeletal remodeling should provide an in vitro model that can be used to increase our understanding of the pathogenesis of Shiga-toxin-mediated cell injury and the role of lipid-raft-mediated cell signaling in cytoskeletal remodeling.

Topics: Actins; Carcinoma; Cell Line; Cell Line, Tumor; Cytoskeletal Proteins; Cytoskeleton; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Humans; Hyaluronan Receptors; Immunoblotting; Immunohistochemistry; Kidney; Kidney Neoplasms; Lipid Metabolism; Microscopy, Confocal; Microscopy, Fluorescence; Models, Biological; Paxillin; Phosphoproteins; Phosphorylation; Protein Binding; Protein-Tyrosine Kinases; RNA; Shiga Toxin; Shiga Toxin 1; Signal Transduction; Time Factors; Trihexosylceramides; Tubulin; Vimentin