Dissecting the Role of the PARylation Stress Response During Tissue Repair and Inflammation in Drosophila

Abstract

In response to injury, tissues (such as the skin) must quickly repair themselves in order to restore barrier integrity. Tissue repair is normally accompanied by a rapid inflammatory response, whereby innate immune cells are recruited to the damaged tissue, where they release toxic mediators (e.g. reactive oxygen species, ROS) to combat invading pathogens and avoid infection. However, these reactive molecules can also significantly damage the host tissue (including subcellular components such as DNA). Therefore, injured tissues upregulate protective pathways to combat this collateral damage. Whilst some of these wound-induced pathways have now been identified, many more stress responses are likely to be involved. Poly(ADP-ribosyl)ation (PARylation) is a well-known stress response to radiation-induced DNA damage that is mediated by Poly(ADP-ribose) polymerase 1 (PARP1). Recent studies on PARP1 hyperactivation have highlighted a negative role for PARylation in the healing process of chronic wounds, however little is known about the role of PARP1 in acute wounds. This study aims to characterise the role of PARylation during wound re-epithelialisation and inflammation using the genetically tractable and translucent Drosophila embryo. We show that PARylation significantly increased following epithelial wounding. Moreover, inhibition of this PARylation response (by RNAi-induced parp knockdown) significantly reduced the rate of wound closure and impaired the formation of the contractile actin cable at the wound edge that normally aids wound contraction. Conversely, knock-down of poly(ADP-ribose) glycohydrolase (PARG), which reverses PARylation, caused a defective wound closure phenotype. Wound-induced inflammation was also impacted by parp knockdown with decreased hemocyte migration to the wound and increased corpse uptake. Taken together, the results of this study highlight a key role for Parp in tissue repair following wounding and suggest that efficient repair requires fine-tuning of the PARylation response. Future work should focus on understanding the underlying molecular mechanism(s), including identification of the targets of PARP1 activity.

Date of Award	3 Oct 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Ian R Collinson (Supervisor) & Helen M A Weavers (Supervisor)