Biology subjects

Meinander, A.

Publications and source records attributed to Meinander, A..

7 recordsLinked to original sources

bioRxiv2026

Dredd-mediated cleavage of Kenny uncouples the IKK complex from selective autophagy to enable innate immunity

Selective autophagy restrains innate immune signalling to maintain tissue homeostasis, yet how this repression is rapidly relieved during infection remains unclear. Here, we show that under basal conditions the inhibitor of {kappa}B kinase {gamma} (IKK{gamma}) Kenny is sequestered at autophagosomes through Atg8 and the selective autophagy receptor Ref(2)P, thereby silencing Imd pathway activity. Bacterial infection disrupts this interaction, releasing the IKK complex to enable immune signalling. Mechanistically, we identify the initiator caspase Dredd as a direct interactor of the IKK{gamma} Kenny and show that Dredd binds and cleaves Kenny in a ubiquitination-dependent manner during infection. This cleavage removes an N-terminal LC3-interacting region, uncoupling the IKK complex from autophagosomal degradation. Dredd-mediated processing of Kenny stabilises the IKK complex and is required for activation of the NF-{kappa}B transcription factor Relish, robust antibacterial responses, and host survival following infection. Together, these findings uncover a mechanism by which caspase-mediated cleavage intersects with selective autophagy to dynamically control NF-{kappa}B signalling during bacterial infection. Short summaryBacterial infection activates NF-{kappa}B signalling by triggering caspase-dependent cleavage of the IKK subunit Kenny, releasing the IKK complex from autophagosomal repression to enable effective innate immune responses.

molecular biology↗

bioRxiv2025

A Mass Spectrometry-Based Interactome Study on Anisomelic Acid and Its Effects on HPV16 E7

Human papillomavirus (HPV)-driven epithelial cancers rely on actions of viral oncoproteins, notably E7, which disrupts cell cycle control through inactivation of the tumor suppressor pRb. While prophylactic vaccines prevent infection, effective therapeutics for existing HPV-associated malignancies remain lacking. Here, we investigate the natural diterpenoid anisomelic acid (AA) and its mechanism of promoting HPV16 E7 degradation. Using cellular thermal shift assay (CETSA), we demonstrate that AA binds to E7, increasing its thermal stability and suggesting a direct molecular interaction. Mass spectrometry-based interactome analysis revealed that AA treatment reshapes the E7 interactome, enriching for E3 ubiquitin ligases (UBR4, TRIP12, TRIM28), the scaffold protein SQSTM1, and HSP40/HSP70 chaperone complexes involved in protein quality control and misfolded protein signaling. These data support a model in which AA binding induces conformational changes in E7 that enhance its recognition by ubiquitin-proteasome and chaperone-mediated degradation pathways. Our findings provide mechanistic insight into AAs antiviral mode of action and highlight its potential as a lead compound for targeted degradation of HPV oncoproteins.

cancer biology↗

bioRxiv2024

M1-linked Ubiquitination by LUBAC Regulates AMPK Activity and the Response to Energetic Stress

Methionine-1 (M1)-linked ubiquitin chains, assembled by the ubiquitin ligase LUBAC and cleaved by the deubiquitinase OTULIN, are critical regulators of inflammation and immune homeostasis. Genetic loss of either LUBAC or OTULIN causes autoinflammatory syndromes, which are associated with defects in glycogen and lipid metabolism. However, how LUBAC and OTULIN regulate metabolic signalling remains unknown. Here, we demonstrate that LUBAC promotes, while OTULIN restricts, activation of the key metabolic regulator AMP-activated protein kinase (AMPK) in cells, mice, and human samples. LUBAC and OTULIN interact with AMPK, control its M1-ubiquitination, and regulate its activation in response to glucose starvation and allosteric activation. During starvation, LUBAC deficiency impairs autophagy induction and hinders the shift from oxidative phosphorylation to glycolysis. Strikingly, LUBAC-deficient Drosophila have a strongly reduced survival rate after starvation. Our work identifies LUBAC and OTULIN as physiological regulators of AMPK, providing the first mechanism by which M1-linked ubiquitin chains regulate metabolic signalling.

cell biology↗

bioRxiv2022

Lamin A/C phosphorylation at serine 22 is a conserved heat shock response to regulate nuclear adaptation during stress

The heat shock (HS) response is crucial for cell survival in harmful environments. Nuclear lamin A/C, encoded by LMNA gene, has been shown to contribute towards altered gene expression during heat shock, but the underlying mechanisms are poorly understood. Here we show that reversible lamin A/C phosphorylation at Ser22 upon HS is an evolutionary conserved stress response that is triggered in concert with HSF1 activation in human and mouse cells and can also be observed in D. melanogaster in vivo. Consequently, the phosphorylation increase facilitated nucleoplasmic localization of lamin A/C and nuclear rounding in response to HS. The importance of lamin phosphorylation equilibria in HS was confirmed by lamin A/C knock-out (KO) cells that showed deformed nuclei after HS and were rescued by ectopic expression of wild-type, but not by a phosphomimetic (S22D) lamin A mutant. Furthermore, HS triggered release of lamina-associated protein 2 (Lap2) from its association with lamin A/C and concurrently its downregulation, a response that was perturbed in lamin A/C KO cells and in LMNA mutant patient fibroblasts. The abrogated Lap2 response resulted in impaired cell cycle arrest under HS and compromised survival at the recovery. Taken together, our results suggest that the altered phosphorylation stoichiometry of lamin A/C provides an evolutionary conserved mechanism to regulate lamin structure and serve nuclear adaptation and cell survival during HS.

molecular biology↗

bioRxiv2021

M1-linked ubiquitination facilitates NF-κB activation during sterile inflammation

Methionine 1 (M1)-linked ubiquitination plays a key role in the regulation of inflammatory nuclear factor-{kappa}B (NF-{kappa}B) signalling and is important for clearance of pathogen infection in Drosophila melanogaster. M1-linked ubiquitin (M1-Ub) chains are assembled by the linear ubiquitin E3 ligase (LUBEL) in flies. Here, we have studied the role of LUBEL in sterile inflammation induced by different types of cellular stresses. We have found that LUBEL catalyses formation of M1-Ub chains in response to hypoxic, oxidative and mechanical stress conditions. LUBEL is shown to be important for flies to survive low oxygen conditions and paraquat-induced oxidative stress. This protective action seems to be driven by stress-induced activation of the NF-{kappa}B transcription factor Relish via the Immune deficiency (Imd) pathway. In addition to LUBEL, the intracellular mediators of Relish activation, including the Drosophila inhibitor of apoptosis (IAP) Diap2, the I{kappa}B kinase {gamma} (IKK{gamma}) Kenny and the initiator caspase Death-related ced-3/Nedd2-like protein (Dredd), but not the membrane receptor peptidoglycan recognition protein (PGRP)-LC, are shown to be required for sterile inflammatory response and survival. Finally, we showed that the stress-induced upregulation of M1-Ub chains in response to hypoxia, oxidative and mechanical stress is also induced in mammalian cells. Taken together, our results suggest that M1-Ub chains are important for NF-{kappa}B signalling in inflammation induced by stress conditions often observed in chronic inflammatory diseases and cancer.

cell biology↗

bioRxiv2020

drICE restrains DIAP2-mediated inflammatory signalling and intestinal inflammation

The Drosophila IAP protein, DIAP2, is a key mediator of NF-κB signalling and is required for immune activation, both locally in the intestinal epithelia and during systemic, fat body-induced responses. We have found that transgenic expression of DIAP2 induces inflammation in the intestine, but not in the fat body, indicating a need for regulating DIAP2 in microbiotic environments. We describe the Drosophila caspase drICE, a known interaction partner of DIAP2, as a regulator of DIAP2 and NF-κB signalling in the intestinal epithelium. drICE acts by cleaving, and interfering with DIAP2’s ability to ubiquitinate and, thereby, activate mediators of the NF-κB pathway. The drICE-cleaved form of DIAP2 is, moreover, unable to induce inflammation during basal conditions in the intestine. Interestingly, cleavage of DIAP2 does not interfere with pathogen-induced signalling, suggesting that drICE protects from immune responses induced by resident microbes. Accordingly, the negative regulatory effect of drICE is lost when rearing flies axenic. Hence, we show that drICE halts unwanted inflammatory signalling in the intestine by forming an inhibitory complex with DIAP2, interfering with the ability of DIAP2 to induce downstream signalling and NF-κB target gene activation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

cell biology↗

bioRxiv2019

Control of MYC-dependent apoptotic threshold by a co-amplified ubiquitin E3 ligase UBR5

MYC protein expression has to be tightly controlled to allow for maximal cell proliferation without inducing apoptosis. Here we discover UBR5 as a novel MYC ubiquitin ligase and demonstrate how it functions as a molecular rheostat to prevent excess accumulation of MYC protein. UBR5 effects on MYC protein stability are independent on N-terminal FBW7 degron of MYC. Endogenous UBR5 inhibition induces MYC protein expression and activates MYC target genes. Moreover, UBR5 governs MYC-dependent phenotypes in vivo in Drosophila. In cancer cells, UBR5-mediated MYC protein suppression diminishes cell killing activity of cancer therapeutics. Further, we demonstrate that UBR5 dominates MYC protein expression at the single-cell level in human basal-type breast cancer tissue. Myc and Ubr5 are co-amplified in MYC-driven human cancer types, and UBR5 controls MYC-mediated apoptotic threshold in co-amplified basal type breast cancer cells. In summary, UBR5 is a novel MYC ubiquitin ligase and an endogenous rheostat for MYC protein expression in vivo. Clinically, expression of UBR5 may be important for protection of breast cancer cells from drug-induced, and MYC-dependent, apoptosis.

cancer biology↗