title: The Mitogen-activated protein kinase p38 links Shiga Toxin-dependent signaling and trafficking.
abstract: Shiga toxin (Stx) binds to the cell, and it is transported via endosomes and the Golgi apparatus to the endoplasmic reticulum and cytosol, where it exerts its toxic effect. We have recently shown that Stx activates the tyrosine kinase Syk, which in turn induces clathrin phosphorylation and up-regulates Stx uptake. Here, we show that toxin-induced signaling can also regulate another step in intracellular Stx transport. We demonstrate that transport of Stx to the Golgi apparatus is dependent on the mitogen-activated protein kinase p38. Treatment of cells with chemical inhibitors or small interfering RNA targeting p38 inhibited Stx transport to the Golgi and reduced Stx toxicity. This p38 dependence is specific to Stx, because transport of the related toxin ricin was not affected by p38 inhibition. Stx rapidly activated p38, and recruited it to early endosomes in a Ca(2+)-dependent manner. Furthermore, agonist-induced oscillations in cytosolic Ca(2+) levels were inhibited upon Stx stimulation, possibly reflecting Stx-dependent local alterations in cytosolic Ca(2+) levels. Intracellular transport of Stx is Ca(2+) dependent, and we provide evidence that Stx activates a signaling cascade involving cross talk between Ca(2+) and p38, to regulate its trafficking to the Golgi apparatus.
authors.affiliation: Department of Biochemistry and Centre for Cancer Biomedicine, Institute for Cancer Research, The Norwegian Radium Hospital, University of Oslo, Montebello, N-0310 Oslo, Norway.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Wälchli
authors.forename: Sigrid S
authors.initials: SS
authors.lastname: Skånland
authors.forename: Tone F
authors.initials: TF
authors.lastname: Gregers
authors.forename: Silje U
authors.initials: SU
authors.lastname: Lauvrak
authors.forename: Maria L
authors.initials: ML
authors.lastname: Torgersen
authors.forename: Ming
authors.initials: M
authors.lastname: Ying
authors.forename: Shun'ichi
authors.initials: S
authors.lastname: Kuroda
authors.forename: Andrés
authors.initials: A
authors.lastname: Maturana
authors.forename: Kirsten
authors.initials: K
authors.lastname: Sandvig
mesh_terms: D002118:Calcium / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D022621:Shiga Toxin / Q000378:metabolism / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism
chemical_list: D047428:Protein Kinase Inhibitors; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D022621:Shiga Toxin; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium