title: A Conserved Structural Motif Mediates Retrograde Trafficking of Shiga Toxin Types 1 and 2.
abstract: Shiga toxin-producing Escherichia coli (STEC) produce two types of Shiga toxin (STx): STx1 and STx2. The toxin A-subunits block protein synthesis, while the B-subunits mediate retrograde trafficking. STEC infections do not have definitive treatments, and there is growing interest in generating toxin transport inhibitors for therapy. However, a comprehensive understanding of the mechanisms of toxin trafficking is essential for drug development. While STx2 is more toxic in vivo, prior studies focused on STx1 B-subunit (STx1B) trafficking. Here, we show that, compared with STx1B, trafficking of the B-subunit of STx2 (STx2B) to the Golgi occurs with slower kinetics. Despite this difference, similar to STx1B, endosome-to-Golgi transport of STx2B does not involve transit through degradative late endosomes and is dependent on dynamin II, epsinR, retromer and syntaxin5. Importantly, additional experiments show that a surface-exposed loop in STx2B (β4-β5 loop) is required for its endosome-to-Golgi trafficking. We previously demonstrated that residues in the corresponding β4-β5 loop of STx1B are required for interaction with GPP130, the STx1B-specific endosomal receptor, and for endosome-to-Golgi transport. Overall, STx1B and STx2B share a common pathway and use a similar structural motif to traffic to the Golgi, suggesting that the underlying mechanisms of endosomal sorting may be evolutionarily conserved.
authors.affiliation: Division of Pharmacology & Toxicology, College of Pharmacy; Institute for Cellular & Molecular Biology, Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Andrey S
authors.initials: AS
authors.lastname: Selyunin
authors.affiliation: Division of Pharmacology & Toxicology, College of Pharmacy; Institute for Cellular & Molecular Biology, Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Somshuvra
authors.initials: S
authors.lastname: Mukhopadhyay
mesh_terms: D020816:Amino Acid Motifs; D016384:Consensus Sequence; D017124:Conserved Sequence; D011992:Endosomes / Q000378:metabolism; D019143:Evolution, Molecular; D005700:Galactosyltransferases / Q000235:genetics; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D021122:Protein Subunits; D021381:Protein Transport; D022622:Shiga Toxin 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D022641:Shiga Toxin 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054323:Shiga-Toxigenic Escherichia coli / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: C107340:GOLIM4 protein, human; D021122:Protein Subunits; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D033921:Vesicular Transport Proteins; C450841:shiga toxin 2 B subunit; D005700:Galactosyltransferases; C045097:UDP-galactose-lactosylceramide alpha 1-4-galactosyltransferase
keywords: Golgi; bacterial toxin; endosome; protein motif; trafficking