M1-linked ubiquitination by LUBEL is required for inflammatory responses to oral infection in Drosophila

Abstract

Post-translational modifications such as ubiquitination play a key role in regulation of inflammatory nuclear factor-κB (NF-κB) signalling. The Drosophila IκB kinase γ (IKKγ) Kenny is a central regulator of the Drosophila Imd pathway responsible for activation of the NF-κB Relish. We found the Drosophila E3 ligase and HOIL-1L interacting protein (HOIP) orthologue linear ubiquitin E3 ligase (LUBEL) to catalyse formation of M1-linked linear ubiquitin (M1-Ub) chains in flies in a signal-dependent manner upon bacterial infection. Upon activation of the Imd pathway, LUBEL modifies Kenny with M1-Ub chains. Interestingly, the LUBEL-mediated M1-Ub chains seem to be targeted both directly to Kenny and to K63-linked ubiquitin chains conjugated to Kenny by DIAP2. This suggests that DIAP2 and LUBEL work together to promote Kenny-mediated activation of Relish. We found LUBEL-mediated M1-Ub chain formation to be required for flies to survive oral infection with Gram-negative bacteria, for activation of Relish-mediated expression of antimicrobial peptide genes and for pathogen clearance during oral infection. Interestingly, LUBEL is not required for mounting an immune response against systemic infection, as Relish-mediated antimicrobial peptide genes can be expressed in the absence of LUBEL during septic injury. Finally, transgenic induction of LUBEL-mediated M1-Ub drives expression of antimicrobial peptide genes and hyperplasia in the midgut in the absence of infection. This suggests that M1-Ub chains are important for Imd signalling and immune responses in the intestinal epithelia, and that enhanced M1-Ub chain formation is able to drive chronic intestinal inflammation in flies.

p47 licenses activation of the immune deficiency pathway in the tick Ixodes scapularis

“…Additional regulation may explain the residual signaling within the I. scapularis IMD network. For example, the Drosophila HOIL-1L interacting protein (HOIP) ortholog linear ubiquitin E3 ligase (LUBEL) works in concert with dIAP2 to activate Relish through methionine 1dependent ubiquitylation of Kenny (66). This is expected, as the transduction of NF-κB is tightly modulated through redundancy to prevent aberrant inflammation and limit fitness costs (7,58).…”

Tanshinone IIA attenuates cardiac microvascular ischemia-reperfusion injury via regulating the SIRT1-PGC1α-mitochondrial apoptosis pathway

“…In addition, the microvascular damage caused by endothelial cell apoptosis and capillary obstruction significantly reduces the effectiveness of reperfusion therapy and may compromise the clinical benefits in patients with AMI (Chrifi et al 2019). Therefore, microvascular damage is upstream of cardiomyocyte damage (Aalto et al 2019). At last, given the direct contact between the Jiankai Zhong and Haichun Ouyang contributed equally to this work.…”

drICE restrains DIAP2-mediated inflammatory signalling and intestinal inflammation

“…To investigate how drICE-mediated cleavage of DIAP2 regulates IMD signalling, we examined the ability of DIAP2 to ubiquitinate its substrates in the presence or absence of active drICE. DIAP2-mediated K63linked ubiquitination of the IMD pathway components IMD and DREDD has been shown to be required for IMD signalling, and the Drosophila NEMO, IKKγ or Kenny, has recently been identified as a target of K63-linked ubiquitination mediated by DIAP2 (Paquette et al, 2010, Meinander et al, 2012, Aalto et al, 2019. While drICE activity was induced by overexpressing drICE in S2 cells, drICE was inhibited by overexpression of the catalytically inactive drICEC211A or by treatment with synthetic caspase-3 inhibitor Z-DEVD-FMK.…”

“…Activation of PGRP-LCx leads to the recruitment of the adaptor proteins IMD and dFADD, and the initiator caspase DREDD (Choe et al, 2005). DREDD-mediated cleavage of IMD exposes a conserved IAP-binding motif that recruits DIAP2 to the complex, stimulating DIAP2-mediated K63-ubiquitination of IMD, DREDD and the IKK Kenny (Paquette et al, 2010, Meinander et al, 2012, Aalto et al, 2019. Ubiquitination of DREDD is needed for cleavage and nuclear localization of the NF-κB protein Relish (Stoven et al, 2003, Meinander et al, 2012, whereas ubiquitination of IMD has been suggested to recruit the Drosophila mitogen-activated protein kinase kinase kinase dTAK1 and the Relish kinase complex IRD5/Kenny to the IMD signalling complex (Ferrandon et al, 2007).…”