Biology subjects

Michalik, D.

Publications and source records attributed to Michalik, D..

2 recordsLinked to original sources

bioRxiv2025

Annexin A2 mediates RIG-I-like receptor responses to viral infection

RIG-I and MDA5 are critical sensors of virus infection and detect many important human pathogens including SARS-CoV-2, influenza A virus (IAV), Zika virus and West Nile virus (WNV). MDA5 is activated by binding to double-stranded RNA generated during infection and induces strong pro-inflammatory and antiviral responses mediated largely via type I interferons. Activation of MDA5 is also implicated in monogenic (e.g. Aicardi-Goutieres syndrome) and complex polygenic (e.g. systemic lupus erythematosus) autoinflammatory diseases, demonstrating the importance of appropriate regulation of this pathway. Yet, how MDA5 is regulated is poorly defined. We employed SILAC-mass spectrometry to discover MDA5 binding partners in virus-infected cells. Our screen revealed Annexin A2 (ANXA2) as an interactor of MDA5 specifically during infection. Direct binding of ANXA2 and MDA5 was recapitulated in vitro and required Ca2+, and ANXA2 promoted MDA5 oligomerisation in cells. Loss of ANXA2 in human cells significantly blunted interferon responses to EMCV, WNV and IAV, demonstrating a role for ANXA2 in activation of both MDA5 and RIG-I. Using human induced pluripotent stem cells, we found that ANXA2 was required for potent neuronal cell responses to WNV infection and macrophage responses to multiple viral pathogens. Thus, we find that ANXA2 is a critical mediator of RIG-I-like receptor pathways.

immunology↗

bioRxiv2021

In vitro reconstitution of divisome activation

Bacterial cell division is coordinated by the Z-ring, a cytoskeletal structure of treadmilling filaments of FtsZ and their membrane anchors, FtsA and ZipA. For divisome maturation and initiation of constriction, the widely conserved actin-homolog FtsA plays a central role, as it links downstream cell division proteins in the membrane to the Z-ring in the cytoplasm. According to the current model, FtsA initiates cell constriction by switching from an inactive polymeric conformation to an active monomeric form, which then stabilizes the Z-ring and recruits downstream proteins such as FtsN. However, direct biochemical evidence for this mechanism is missing so far. Here, we used biochemical reconstitution experiments in combination with quantitative fluorescence microscopy to study the mechanism of divisome activation in vitro. By comparing the properties of wildtype FtsA and FtsA R286W, a gain-of-function mutant thought to mimic its active state, we found that active FtsA outperforms the wildtype protein in replicating FtsZ treadmilling dynamics, filament stabilization and FtsN recruitment. We could attribute these differences to a faster membrane exchange of FtsA R286W as well as its higher packing density below FtsZ filaments. Using FRET microscopy, we also show that binding of FtsN does not compete with, but promotes FtsA self-interaction. Together, our findings shed new light on the assembly and activation of the bacterial cell division machinery and the mechanism of how FtsA initiates cell constriction.

biochemistry↗