title: Differential response of the human renal proximal tubular epithelial cell line HK-2 to Shiga toxin types 1 and 2.
abstract: Shiga toxins (Stxs) are expressed by the enteric pathogens Shigella dysenteriae serotype 1 and certain serotypes of Escherichia coli. Stx-producing bacteria cause bloody diarrhea with the potential to progress to acute renal failure. Stxs are potent protein synthesis inhibitors and are the primary virulence factors responsible for renal damage that may follow diarrheal disease. We explored the use of the immortalized human proximal tubule epithelial cell line HK-2 as an in vitro model of Stx-induced renal damage. We showed that these cells express abundant membrane Gb(3) and are differentially susceptible to the cytotoxic action of Stxs, being more sensitive to Shiga toxin type 1 (Stx1) than to Stx2. At early time points (24 h), HK-2 cells were significantly more sensitive to Stxs than Vero cells; however, by 72 h, Vero cell monolayers were completely destroyed while some HK-2 cells survived toxin challenge, suggesting that a subpopulation of HK-2 cells are relatively toxin resistant. Fluorescently labeled Stx1 B subunits localized to both lysosomal and endoplasmic reticulum (ER) compartments in HK-2 cells, suggesting that differences in intracellular trafficking may play a role in susceptibility to Stx-mediated cytotoxicity. Although proinflammatory cytokines were not upregulated by toxin challenge, Stx2 selectively induced the expression of two chemokines, macrophage inflammatory protein-1α (MIP-1α) and MIP-1β. Stx1 and Stx2 differentially activated components of the ER stress response in HK-2 cells. Finally, we demonstrated significant poly(ADP-ribose) polymerase (PARP) cleavage after exposure to Stx1 or Stx2. However, procaspase 3 cleavage was undetectable, suggesting that HK-2 cells may undergo apoptosis in response to Stxs in a caspase 3-independent manner.
authors.affiliation: Department of Microbial and Molecular Pathogenesis, College of Medicine, Texas A&M Health Science Center, Bryan, Texas 77807, USA.
authors.forename: Erin K
authors.initials: EK
authors.lastname: Lentz
authors.forename: Dinorah
authors.initials: D
authors.lastname: Leyva-Illades
authors.forename: Moo-Seung
authors.initials: MS
authors.lastname: Lee
authors.forename: Rama P
authors.initials: RP
authors.lastname: Cherla
authors.forename: Vernon L
authors.initials: VL
authors.lastname: Tesh
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000096:biosynthesis; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000096:biosynthesis / Q000187:drug effects; D002460:Cell Line; D054405:Chemokine CCL3 / Q000096:biosynthesis / Q000187:drug effects; D054407:Chemokine CCL4 / Q000096:biosynthesis / Q000187:drug effects; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000187:drug effects; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects*; D008247:Lysosomes / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D022622:Shiga Toxin 1 / Q000494:pharmacology* / Q000633:toxicity; D022641:Shiga Toxin 2 / Q000494:pharmacology* / Q000633:toxicity; D012762:Shigella dysenteriae / Q000166:cytology / Q000378:metabolism; D014709:Vero Cells / Q000187:drug effects
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D054405:Chemokine CCL3; D054407:Chemokine CCL4; C472766:Gb3 antigen; D011500:Protein Synthesis Inhibitors; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3