Submitted on December 4, 2008
Revised on April 7, 2009
Accepted on April 8, 2009
Tristetraprolin regulates IL-8 mRNA stability in cystic fibrosis lung epithelial cells
Nagaraja Sethuraman Balakathiresan1, Sharmistha Bhattacharyya1, Usha Gutti1, Robert P Long1, Catherine Jozwik1, Wei Huang2, Meera Srivastava2, Harvey B. Pollard2, and Roopa Biswas3*
1 USUHS
2 Uniformed Services University of the Health Sciences
3 Uniformed Sevices University of Health Sciences
* To whom correspondence should be addressed. E-mail: rbiswas{at}usuhs.mil.
Cystic fibrosis (CF) is due to mutations in the CFTR gene, and is characterized by hyper-secretion of the proinflammatory chemokine interleukin 8 (IL-8) into the airway lumen. Consequently this induces the highly inflammatory cellular phenotype typical of CF. Our initial studies revealed that IL-8 mRNA is relatively stable in CF cells compared to those that had been repaired with [WT]CFTR. Relevantly, the 3'-UTR of IL-8 mRNA contains AU-rich sequences (AREs) that have been shown to mediate post-transcriptional regulation of pro-inflammatory genes upon binding to ARE binding proteins including Tristetraprolin (TTP). We therefore hypothesized that very low endogenous levels of TTP in CF cells might be responsible for the relative stability of IL-8 mRNA. As predicted, increased expression of TTP in CF cells resulted in reduced stability of IL-8 mRNA. An in vitro analysis of IL-8 mRNA stability in CF cells also revealed a TTP-induced enhancement of deadenylation causing reduction of IL-8 mRNA stability. We conclude that enhanced stability of IL-8 mRNA in TTP deficient CF lung epithelial cells serve to drive the pro-inflammatory cellular phenotype in the CF lung.
