The RNA-binding Protein HuR Stabilizes Cytosolic Phospholipase A2α mRNA under Interleukin-1β Treatment in Non-small Cell Lung Cancer A549 Cells

The activation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha) plays an important role in initiating the inflammatory response. The regulation of cPLA(2)alpha mRNA turnover has been proposed to control cPLA(2)alpha gene expression under cytokine and growth factor stimulation. However, the detailed mechanism is still unknown. In this report, we have demonstrated that the cPLA(2)alpha mRNA stability was increased under IL-1 beta treatment in A549 cells. By using EMSAs, HuR was identified as binding with the cPLA(2)alpha mRNA 3'-UTR, and the binding region was located at nucleotides 2716-2807, a fragment containing AUUUA flanked by U-rich sequences. IL-1 beta treatment enhanced the association of cPLA(2)alpha mRNA with cytosolic HuR. The reduction of HuR expression by RNA interference technology inhibited IL-1 beta-induced cPLA2 alpha mRNA and protein expression. Furthermore, blocking the p38 MAPK signaling pathway with SB203580 abolished the effect of IL-1 beta-induced cPLA(2)alpha gene expression. Phosphorylation at residue Thr-118 of HuR is crucial in regulating the interaction between HuR and its target mRNAs. Mutation of HuR Thr-118 reduced the association between HuR and cPLA(2)alpha mRNA under IL-1 beta treatment. This inhibitory effect was also observed in binding with COX-2 mRNA. This result indicated that p38 MAPK-mediated Thr-118 phosphorylation may play a key role in regulating the interaction of HuR with its target mRNAs in inflammation.