title: Shiga toxin increases formation of clathrin-coated pits through Syk kinase.
abstract: Clathrin-dependent endocytosis is a main entry mechanism for the glycolipid-binding Shiga toxin (Stx), although clathrin-independent pathways are also involved. Binding of Stx to its receptor Gb3 not only is essential for Stx retrograde transport to the endoplasmic reticulum and toxicity but also activates signaling through the tyrosine kinase Syk. We previously described that Syk activity is important for Stx entry, but it remained unclear how this kinase modulates endocytosis of Stx. Here we characterized the effects of Stx and Syk on clathrin-coated pit formation. We found that acute treatment with Stx results in an increase in the number of clathrin-coated profiles as determined by electron microscopy and on the number of structures containing the endocytic AP-2 adaptor at the plasma membrane determined by live-cell spinning disk confocal imaging. These responses to Stx require functional Syk activity. We propose that a signaling pathway mediated by Syk and modulated by Stx leads to an increased number of endocytic clathrin-coated structures, thus providing a possible mechanism by which Stx enhances its own endocytosis.
authors.affiliation: Centre for Cancer Biomedicine, Faculty Division the Norwegian Radium Hospital, University of Oslo, Oslo, Norway.
authors.forename: Audrun
authors.initials: A
authors.lastname: Utskarpen
authors.forename: Ramiro
authors.initials: R
authors.lastname: Massol
authors.forename: Bo
authors.initials: B
authors.lastname: van Deurs
authors.forename: Silje Ugland
authors.initials: SU
authors.lastname: Lauvrak
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Sandvig
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D045744:Cell Line, Tumor; D002966:Clathrin / Q000378:metabolism*; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism* / Q000648:ultrastructure*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D022621:Shiga Toxin / Q000494:pharmacology*; D000072377:Syk Kinase
chemical_list: D033962:Adaptor Protein Complex 2; D002966:Clathrin; D047908:Intracellular Signaling Peptides and Proteins; D022621:Shiga Toxin; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase