Investigating the role of Pellino1, an E3 ubiquitin ligase, in modulating the signalling pathways that control the inflammatory response

Pellino1 was identified as an IRAK binding partner and is involved in Lysine-63 polyubiquitination of IRAK 1/4 and RIP1, which are key mediators of the TLR and IL-1R signalling pathways. As such, these pathways are implicated in responses to bacterial and viral infections and common respiratory viruses, such as rhinovirus, are a major cause of asthma exacerbations. The functional importance of Pellino proteins in regulating immune responses and their role in airway inflammatory diseases is yet to be elucidated. We hypothesised that Pellino1 would play a critical role in regulating the inflammatory response in the lung airway epithelium. Expression and regulation of the Pellino family was investigated at the transcriptional level. Pellino1 was knocked down in the human bronchial airway epithelial cell line BEAS-2B and PBECs using targeted siRNA. Pellino1 is expressed in BEAS-2B and PBECs. Pellino1 knockdown led to reduced IL-8 generation in response to IL-1β and a viral mimic poly(I:C) stimulation in BEAS-2B, however RANTES production was unchanged. In contrast to the BEAS-2B, the PBECs exhibited preserved IL-1 signalling. However, these cells also showed a reduction in IL-8 production in response to both poly(I:C) stimulation and RV1B infection. Pellino1 knockdown had no effect on RANTES production. Knockdown of a putative Pellino1 target, RIP1, in PBECs leads to the significant increase in IL-8 generation in response to poly(I:C), suggesting that it may act as a negative regulator of the TLR3 signalling pathway in these cells. PBECs may utilise the non-canonical NF-κB signalling pathway in response to poly(I:C) stimulation. Pellino1 knockdown leads to reduced IL-8 production in response to a viral mimic poly(I:C) in lung airway epithelial cells and the natural pathogen RV1B in PBECs. These data indicate that Pellino1 regulates proinflammatory responses in airway epithelium and may be a feasible target to downregulate neutrophilic airway inflammation whilst retaining antiviral immunity, which would be highly beneficial in the treatment of chronic airway inflammatory disorders such as asthma and COPD.