Role of ubiquitin and ubiquitin-like proteins in the regulation of HLH-30/TFEB-TFE3 pathway-dependent signalling and immune response
Using the Caenorhabditis elegans model, the transcription factor HLH-30/TFEB was identified as a major conserved player in the immune response during Staphylococcus aureus infection. Ubiquitination is an evolutionarily conserved posttranslational modification that is involved in the regulation of many physiological processes, including many physiological processes, including innate immunity. My thesis investigates the role of ubiquitination in the HLH-30/TFEB-dependent host response by identifying and characterising the ubiquitin ligase (E3s) and deubiquitinase (DUBs) enzymes that regulate HLH-30/TFEB upstream signalling and the HLH-30/TFEB-dependent immune response. HLH-30 dependent immune response. In the first part of my thesis, I was able to In the first part of my thesis, I was able to set up a reporter strain of HLH-30 activity that allowed me to identify the E3 enzymes WWP-1 and DUB USP- 5 by RNAi screen. I showed that WWP- 1 and USP-5 all regulate HLH-30 activity. 1 and USP-5 both regulate the HLH-30 dependent transcriptional response and animal survival during infection. I observed that WWP-1 is predominantly expressed in intestinal cells, where it regulates HLH-30 protein levels in a cell-autonomous manner, whereas USP-5 appears to regulate nucleus-cytoplasm trafficking of HLH-30 and its role is not restricted to the intestine. In a second part of my thesis, I was able to identify the E3-F-box subunit FBXL-1 as being induced during infection via HLH-30 and that its expression is required specifically in host defence against S. aureus without being involved in the heat shock induced proteostatic stress response. Taken together, this work revealed the importance of ubiquitination in HLH-30/TFEB pathway-dependent host defence.
Innate immunity; ubiquitination; C. elegans; signalling; HLH-30; TFEB
Dr Robert BALLOTTI
Dr Bénédicte PY
Dr Lionel PINTARD
Dr Jolanta POLANOWSKA