Elevated furin levels in human cystic fibrosis cells result in hypersusceptibility to exotoxin A–induced cytotoxicity
Wojciech Ornatowski, … , Jennifer L. Taylor-Cousar, Vojo Deretic
Wojciech Ornatowski, … , Jennifer L. Taylor-Cousar, Vojo Deretic
Published October 18, 2007
Citation Information: J Clin Invest. 2007;117(11):3489-3497. https://doi.org/10.1172/JCI31499.
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Research Article Cell biology

Elevated furin levels in human cystic fibrosis cells result in hypersusceptibility to exotoxin A–induced cytotoxicity

Abstract

Progressive pulmonary disease and infections with Pseudomonas aeruginosa remain an intractable problem in cystic fibrosis (CF). At the cellular level, CF is characterized by organellar hyperacidification, which results in altered protein and lipid glycosylation. Altered pH of the trans-Golgi network (TGN) may further disrupt the protein processing and packaging that occurs in this organelle. Here we measured activity of the major TGN endoprotease furin and demonstrated a marked upregulation in human CF cells. Increased furin activity was linked to elevated production in CF of the immunosuppressive and tissue remodeling cytokine TGF-β and its downstream effects, including macrophage deactivation and augmented collagen secretion by epithelial cells. As furin is responsible for the proteolytic processing of a range of endogenous and exogenous substrates including growth factors and bacterial toxins, we determined that elevated furin-dependent activation of exotoxin A caused increased cell death in CF respiratory epithelial cells compared with genetically matched CF transmembrane conductance regulator–corrected cells. Thus elevated furin levels in CF respiratory epithelial cells contributes to bacterial toxin–induced cell death, fibrosis, and local immunosuppression. These data suggest that the use of furin inhibitors may represent a strategy for pharmacotherapy in CF.

Authors

Wojciech Ornatowski, Jens F. Poschet, Elizabeth Perkett, Jennifer L. Taylor-Cousar, Vojo Deretic

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Figure 4

CF cells are more sensitive to P. aeruginosa ExoA.

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CF cells are more sensitive to P. aeruginosa ExoA. CF an...
CF and matched non-CF respiratory epithelial cells were cultured overnight in 96-well plates with media containing 10% serum. Cells were incubated with ExoA for 24 hours. Cell viability was measured by adding WST-1 as described in Methods. (A) AS1 normal human respiratory epithelial cells stably transfected with CFTR antisense construct (inducing CF phenotype) and their matching control S1 (cells stably transfected with the sense construct). (B) pCEP-R (overexpressing the dominant-negative CFTR R domain) and pCEP (mock-transfected). (C) IB3-1 and S9 (CFTR corrected). Human lung epithelial cells were incubated with furin inhibitor CMK (50 μM) for 24 hours at 37°C. (D) Dose-dependent cytotoxicity of ExoA. Lung epithelial cells were treated for 24 hours with increasing concentrations of P. aeruginosa ExoA (0 to 3,000 ng/ml). Data are presented as percentage of live cells, for which 100% corresponds to ExoA untreated cells (n = 3 experiments). Mean ± SEM (*P < 0.05, **P < 0.01, †P ≥ 0.05).