Lung epithelial injury by B. anthracis lethal toxin is caused by MKK-dependent loss of cytoskeletal integrity.
Bacillus anthracis lethal toxin (LT) is a key virulence factor of anthrax and contributes significantly to the in vivo pathology. The enzymatically active component is a Zn(2+)-dependent metalloprotease that cleaves most isoforms of mitogen-activated protein kinase kinases (MKKs). Using ex vivo differentiated human lung epithelium we report that LT destroys lung epithelial barrier function and wound healing responses by immobilizing the actin and microtubule network. Long-term exposure to the toxin generated a unique cellular phenotype characterized by increased actin filament assembly, microtubule stabilization, and changes in junction complexes and focal adhesions. LT-exposed cells displayed randomly oriented, highly dynamic protrusions, polarization defects and impaired cell migration. Reconstitution of MAPK pathways revealed that this LT-induced phenotype was primarily dependent on the coordinated loss of MKK1 and MKK2 signaling. Thus, MKKs control fundamental aspects of cytoskeletal dynamics and cell motility. Even though LT disabled repair mechanisms, agents such as keratinocyte growth factor or dexamethasone improved epithelial barrier integrity by reducing cell death. These results suggest that co-administration of anti-cytotoxic drugs may be of benefit when treating inhalational anthrax.
Lehmann
Mandy
M
Department of Immunology & Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America.
Noack
Deborah
D
Wood
Malcolm
M
Perego
Marta
M
Knaus
Ulla G
UG
D008841:Actin Cytoskeleton / Q000378:metabolism; D000942:Antigens, Bacterial / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001427:Bacterial Toxins / Q000494:pharmacology*; D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects* / Q000502:physiology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006801:Humans; D016086:Lentivirus; D055370:Lung Injury / Q000201:enzymology* / Q000473:pathology*; D008666:Metalloendopeptidases / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D014945:Wound Healing
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; C030325:anthrax toxin; D020929:Mitogen-Activated Protein Kinase Kinases; D008666:Metalloendopeptidases; D020558:GTP Phosphohydrolases