Biology subjects

Labzin, L. I.

Publications and source records attributed to Labzin, L. I..

3 recordsLinked to original sources

bioRxiv2023

Cerebral Cavernous Malformation severity is impacted by distinct forms of Hyaluronic acid in the vascular microenvironment

Cerebral Cavernous Malformations (CCMs) are vascular lesions that predominantly form in blood vessels of the central nervous system (CNS) upon loss of the CCM multimeric protein complex. The endothelial cells (ECs) within CCM lesions are characterised by overactive MEKK3 kinase and KLF2/4 transcription factor signalling, leading to pathological changes such as increased EC spreading and reduced junctional integrity. Concomitant to aberrant EC signalling, non-autonomous signals from the extracellular matrix (ECM) have also been implicated in CCM lesion growth and these factors might explain why CCM lesions mainly develop in the CNS. Here, we adapted a three dimensional (3D) microfluidic system to examine CCM1 deficient human micro-vessels in distinctive ECMs. We validate that EC pathological hallmarks are maintained in this 3D model. We further show that key genes responsible for homeostasis of Hyaluronic Acid (HA), a major ECM component of the CNS, are dysregulated in CCM. Supplementing the ECM in our model with forms of HA that are predicted to be reduced, inhibits CCM cellular phenotypes, independent of KLF2/4. This study thereby provides a proof-of-principle that ECM embedded 3D microfluidic models are ideally suited to identify how changes in ECM structure and signalling impact vascular malformations.

cell biology↗

bioRxiv2023

Caspase-4 dimerisation and D289 auto-processing elicits an interleukin-1β converting enzyme

The non-canonical inflammasome is a signalling complex critical for cell defence against cytosolic Gram-negative bacteria. A key step in the human non-canonical inflammasome pathway involves unleashing the proteolytic activity of caspase-4 within this complex. Caspase-4 induces inflammatory responses by cleaving gasdermin-D (GSDMD) to initiate pyroptosis, although the molecular mechanisms that activate caspase-4 and govern its capacity to cleave substrates are poorly defined. Caspase-11, the murine counterpart of caspase-4, acquires protease activity within the non-canonical inflammasome by forming a dimer that self-cleaves at D285 to directly cleave GSDMD. These cleavage events trigger signalling via the NLRP3-ASC-caspase-1 axis, leading to downstream cleavage of the pro-interleukin-1{beta} (pro-IL-1{beta}) cytokine precursor. Here, we show that caspase-4 first dimerises then self-cleaves at two sites - D270 and D289 - in the interdomain linker to acquire full proteolytic activity, cleave GSDMD and induce cell death. Surprisingly, caspase-4 dimerisation and self-cleavage at D289 generates a caspase-4 p34/p9 protease species that directly cleaves pro-IL-1{beta}, resulting in its maturation and secretion independently of the NLRP3 inflammasome in primary human myeloid and epithelial cells. Our study thus elucidates the key molecular events that underpin signalling by the caspase-4 inflammasome, and identifies IL-1{beta} as a natural substrate of caspase-4.

immunology↗

bioRxiv2022

ACE2 is necessary for SARS-CoV-2 infection and sensing by macrophages but not sufficient for productive viral replication

Macrophages are key cellular contributors to COVID-19 pathogenesis. Whether SARS-CoV-2 can enter macrophages, replicate and release new viral progeny remains controversial. Similarly, whether macrophages need to sense replicating virus to drive cytokine release is also unclear. Macrophages are heterogeneous cells poised to respond to their local microenvironment, and accordingly, the SARS-CoV-2 entry receptor ACE2 is only present on a subset of macrophages at sites of human infection. Here, we use in vitro approaches to investigate how SARS-CoV-2 interacts with ACE2-negative and ACE2-positive human macrophages and determine how these macrophage populations sense and respond to SARS-CoV-2. We show that SARS-CoV-2 does not replicate within ACE2-negative human macrophages and does not induce pro-inflammatory cytokine expression. By contrast, ACE2 expression in human macrophages permits SARS-CoV-2 entry, replication, and virion release. ACE2-expressing macrophages sense replicating virus to trigger pro-inflammatory and anti-viral programs that limit virus release. These combined findings resolve several controversies regarding macrophage-SARS-CoV-2 interactions and identify a signaling circuit by which macrophages sense SARS-CoV-2 cell entry and respond by restricting viral replication. One sentence summaryLack of macrophage ACE2 expression precludes SARS-CoV-2 entry and sensing, while ACE2-expressing macrophages sense intramacrophage SARS-CoV-2 replication to induce rapid anti-viral responses that limit new virion release.

immunology↗