Biology subjects

Schmeing, M.

Publications and source records attributed to Schmeing, M..

4 recordsLinked to original sources

bioRxiv2025

Pantetheinamides that inhibit the growth of intracellular Salmonella Typhimurium

The metabolic adaptability of intracellular pathogens, such as the Gram-negative Salmonella enterica serovar Typhimurium (STm), enables their survival in nutrient-restricted host environments, while also presenting an opportunity for selective antimicrobial targeting. Herein, we report the synthesis and screening of a small pantetheinamide library aimed at inhibiting the proliferation of STm within macrophages. Two lead compounds exhibited selective activity against intracellular STm and reduced bacterial burden in a murine colitis model. Mechanistic studies suggest their primary mode of action to be the inhibition of coenzyme A (CoA) biosynthesis via the PanD-PanZ regulatory complex, which is absent in host cells. Importantly, resistance pressure to our compound was shown to be significantly stronger in nutrient-limited media compared to nutrient-rich media, supporting the targeting of nutrient stress as a strategy to delay resistance. This work highlights the value of inhibiting pathogen-specific metabolic vulnerabilities in combination with host defence mechanisms to develop novel antimicrobials.

microbiology↗

bioRxiv2024

Mechanisms of PP2A-Ankle2 dependent nuclear reassembly after mitosis

In animals, mitosis involves the breakdown of the nucleus. The reassembly of a nucleus after mitosis requires the reformation of the nuclear envelope around a single mass of chromosomes. This process requires Ankle2 (also known as LEM4 in humans) which interacts with PP2A and promotes the function of Barrier-to-Autointegration Factor (BAF). Upon dephosphorylation, BAF dimers cross-bridge chromosomes and bind lamins and transmembrane proteins of the reassembling nuclear envelope. How Ankle2 functions in mitosis is incompletely understood. Using a combination of approaches in Drosophila, along with structural modeling, we provide several lines of evidence that suggest that Ankle2 is a regulatory subunit of PP2A, explaining how it promotes BAF dephosphorylation. In addition, we discovered that Ankle2 interacts with the endoplasmic reticulum protein Vap33, which is required for Ankle2 localization at the reassembling nuclear envelope during telophase. We identified the interaction sites of PP2A and Vap33 on Ankle2. Through genetic rescue experiments, we show that the Ankle2/PP2A interaction is essential for the function of Ankle2 in nuclear reassembly and that the Ankle2/Vap33 interaction also promotes this process. Our study sheds light on the molecular mechanisms of post-mitotic nuclear reassembly and suggests that the endoplasmic reticulum is not merely a source of membranes in the process, but also provides localized enzymatic activity.

cell biology↗

bioRxiv2023

Repression of mRNA translation initiation by GIGYF1 via blocking the eIF3-eIF4G1 interaction

Viruses commonly interfere with the function of the eukaryotic translation initiation factor 4G1 (eIF4G1), a pivotal factor in the recruitment of the eIF3 complex and ribosome to the mRNA. This results in the inhibition of general host protein synthesis and redirecting ribosomes toward viral mRNAs. Certain viruses also selectively repress the translation of mRNAs involved in the host antiviral response. GIGYF2 and its interacting cap-binding protein 4EHP enable the transcript-specific repression of mRNA translation mediated by microRNAs and RNA-binding proteins (RBPs). RNA viruses, such as SARS-CoV-2, exploit the GIGYF2/4EHP complex to selectively repress the translation of transcripts such as Ifnb1 mRNA, which encodes the antiviral cytokine Interferon {beta} (IFN-{beta}). Herein, we reveal that GIGYF1, a paralogue of GIGYF2, robustly represses cellular mRNA translation through a distinct mechanism independent of 4EHP. Upon recruitment to a target mRNA by RBPs, the C-terminal region of GIGYF1 binds to subunits of eIF3 at the interaction interface of eIF3-eIF4G1. This disrupts binding of eIF3 to eIF4G1, resulting in mRNA-specific translational repression. This mechanism exerts profound influences on the host cells response to viral infection. Depletion of GIGYF1 induces a robust immune response by derepressing Ifnb1 mRNA translation. Overall, our study highlights a unique mechanism of translational regulation by GIGYF1 that involves sequestering eIF3 and abrogating its binding to eIF4G1. This mechanism can be utilized by RBPs that interact with GIGYF1 to specifically repress the translation of their target mRNAs, significantly affecting critical biological processes, including host-pathogen interactions.

cell biology↗

bioRxiv2023

Structure and function of a hexameric cyanophycin synthetase 2

Cyanophycin is a natural polymer composed of a poly-aspartate backbone with arginine attached to each of the aspartate sidechains. Produced by a wide range of bacteria, which mainly use it as a store of fixed nitrogen, it has many promising industrial applications. Cyanophycin can be synthesized from the amino acids Asp and Arg by the widespread cyanophycin synthetase 1 (CphA1), or from the dipeptide {beta}-Asp-Arg by the cyanobacterial enzyme cyanophycin synthetase 2 (CphA2). CphA2 enzymes display a range of oligomeric states, from dimers to dodecamers. Recently, the crystal structure of a CphA2 dimer was solved but could not be obtained in complex with substrate. Here, we report cryo-EM structures of the hexameric CphA2 from Stanieria sp. at ~2.8 [A] resolution, both with and without ATP and cyanophycin. The structures show a trimer-of-dimers hexameric architecture, and substrate-binding interactions that are similar to those of CphA1. Mutagenesis experiments demonstrate the importance of several conserved substrate-binding residues. We also find that a Q416A/R528G double mutation prevents hexamer formation and use this double mutant to show that hexamerization augments the rate of cyanophycin synthesis. Together, these results increase our mechanistic understanding of how an interesting green polymer is biosynthesized.

biochemistry↗