Biology subjects

Nachbur, U.

Publications and source records attributed to Nachbur, U..

5 recordsLinked to original sources

bioRxiv2025

ZnF-UBP domains regulate deubiquitinase activity by relieving ubiquitin product inhibition

Most ubiquitin specific protease (USP) deubiquitinases (DUBs) combine non-selective catalytic domains with one or multiple exo-domains that contribute substrate specificity and localisation, but are generally poorly characterised. Zinc-Finger UBP (ZnF-UBP) domains exist in 12 USP DUBs, yet their function is unclear. We here comprehensively analyse human ZnF-UBP domains, and reveal that 8 of 14 bind ubiquitin (Ub), via an unattached Ub C-terminal GlyGly motif. We focus on USP16, a nucleosome DUB with activity for Ub and Ub-like modifiers, and show that whilte its ZnF-UBP domain can bind substrates, it is also a crucial contributor to enzyme kinetics. Slow Ub release from the catalytic domain after cleavage causes product inhibition, which is overcome in cis by ZnF-UBP-mediated product release. Interestingly, supplying a high affinity product-capturing ZnF-UBP domain in trans, activates USP16 and other USP enzymes. Our data shows the importance of product inhibition as a regulatory mechanism in DUBs, and exemplifies the unappreciated role of exo-domains in regulating DUB function beyond substrate binding.

biochemistry↗

bioRxiv2022

MLKL deficiency protects against low-grade, sterile inflammation in aged mice

MLKL and RIPK3 are the core signaling proteins of the inflammatory cell death pathway, necroptosis, which is a known mediator and modifier of human disease. Necroptosis has been implicated in the progression of disease in almost every physiological system and recent reports suggest a role for necroptosis in aging. Here we present the first comprehensive analysis of age-related histopathological and immunological phenotypes in a cohort of Mlkl-/- and Ripk3-/- mice on a congenic C57BL/6J genetic background. We show that genetic deletion of Mlkl, but not Ripk3, in female mice interrupts immune system aging, specifically delaying the age-related reduction of circulating lymphocytes. Mlkl-/- female mice were also protected against age-related, low-grade chronic sterile inflammation, with a reduced number of inflammatory infiltrates present in the connective and muscle tissue at 17 months relative to wild-type littermates. These observations implicate MLKL in age-related sterile inflammation, suggesting a possible application for long-term anti-necroptotic therapy in humans.

immunology↗

bioRxiv2021

Oligomerization-driven MLKL ubiquitylation antagonises necroptosis

Mixed lineage kinase domain-like (MLKL) is the executioner in the caspase-independent form of programmed cell death called necroptosis. Receptor Interacting serine/threonine Protein Kinase 3 (RIPK3) phosphorylates MLKL, triggering MLKL oligomerization, membrane translocation and membrane disruption. MLKL also undergoes ubiquitylation during necroptosis, yet neither the mechanism nor significance of this event have been demonstrated. Here we show that necroptosis-specific, multi-mono-ubiquitylation of MLKL occurs following its activation and oligomerization. Ubiquitylated MLKL accumulates in a digitonin insoluble cell fraction comprising plasma/organellar membranes and protein aggregates. This ubiquitylated form is diminished by a plasma membrane located deubiquitylating enzyme. MLKL is ubiquitylated on at least 4 separate lysine residues once oligomerized, and this correlates with proteasome- and lysosome-dependent turnover. Using a MLKL-DUB fusion strategy, we show that constitutive removal of ubiquitin from MLKL licences MLKL auto-activity independent of necroptosis signalling in mouse and human cells. Therefore, besides its role in the kinetic regulation of MLKL-induced death following an exogenous necroptotic stimulus, ubiquitylation also contributes to the restraint of basal levels of activated MLKL to avoid errant cell death.

molecular biology↗

bioRxiv2020

A regulatory interface on RIPK2 is required for XIAP binding and NOD signaling activity

Signaling via the intracellular pathogen receptors Nucleotide-binding oligomerization domain-containing proteins NOD1 and NOD2 requires Receptor Interacting Kinase 2 (RIPK2), an adaptor kinase that can be targeted for the treatment of various inflammatory diseases. However, the molecular mechanisms of how RIPK2 contributes to NOD signaling are not completely understood. We generated FLAG-tagged RIPK2 knock-in mice using CRISPR/Cas9 technology to study NOD signaling mechanisms at the endogenous level. Using cells from these mice we were able to generate a detailed map of post-translational modifications on RIPK2 during NOD signaling and we identified a new regulatory interface on RIPK2, which dictates the crucial interaction with the E3 ligase XIAP.

cell biology↗

bioRxiv2019

NOD1 mediates non-canonical inflammasome processing of interleukin-18 in epithelial cells to Helicobacter pylori infection.

The interleukin-1 family members, IL-1{beta} and IL-18, are processed into their biologically active forms by multi-protein complexes, known as inflammasomes. Although the inflammasome pathways that mediate IL-1{beta} processing in myeloid cells have been extensively studied, those involved in IL-18 processing, particularly in non-myeloid cells, are still poorly understood. Here, we have identified the cytosolic sensor NOD1 as a key regulator of IL-18 processing in epithelial cells responding to Helicobacter pylori infection. Importantly, NOD1 processing of IL-18 occurs independently of the canonical inflammasome proteins, NLRP3 and ASC. Instead, NOD1 interacts directly with caspase-1 via homotypic binding of caspase-activation recruitment domains. We show that IL-18 is important in maintaining tissue homeostasis and protecting against pre-neoplastic changes due to gastric H. pylori infection. These findings reveal an unanticipated role for NOD1 in a new type of inflammasome that regulates epithelial cell production of bioactive IL-18 with tissue protective functions.

immunology↗