The Myxobacterial Antibiotic Myxovalargin: Biosynthesis, Structural Revision, Total Synthesis, and Molecular Characterization of Ribosomal Inhibition

Resistance of bacterial pathogens against antibiotics is declared by WHO as a major global health threat. As novel antibacterial agents are urgently needed, we re-assessed the broad-spectrum myxobacterial antibiotic myxovalargin and found it to be extremely potent against Mycobacterium tuberculosis. To ensure compound supply for further development, we studied myxovalargin biosynthesis in detail enabling production via fermentation of a native producer. Feeding experiments as well as functional genomics analysis suggested a structural revision, which was eventually corroborated by the development of a concise total synthesis. The ribosome was identified as the molecular target based on resistant mutant sequencing, and a cryo-EM structure revealed that myxovalargin binds within and completely occludes the exit tunnel, consistent with a mode of action to arrest translation during a late stage of translation initiation. These studies open avenues for structure-based scaffold improvement toward development as an antibacterial agent

Entwicklung neuartiger gewebespezifischer Therapiekonzepte zur Behandlung von Diabetes

Abstract unter Embargo bis Juni 202

Conformational tuning improves the stability of spirocyclic nitroxides with long paramagnetic relaxation times

Abstract Nitroxides are widely used as probes and polarization transfer agents in spectroscopy and imaging. These applications require high stability towards reducing biological environments, as well as beneficial relaxation properties. While the latter is provided by spirocyclic groups on the nitroxide scaffold, such systems are not in themselves robust under reducing conditions. In this work, we introduce a strategy for stability enhancement through conformational tuning, where incorporating additional substituents on the nitroxide ring effects a shift towards highly stable closed spirocyclic conformations, as indicated by X-ray crystallography and density functional theory (DFT) calculations. Closed spirocyclohexyl nitroxides exhibit dramatically improved stability towards reduction by ascorbate, while maintaining long relaxation times in electron paramagnetic resonance (EPR) spectroscopy. These findings have important implications for the future design of new nitroxide-based spin labels and imaging agents

Conformational tuning improves the stability of spirocyclic nitroxides with long paramagnetic relaxation times

Nitroxides are widely used as probes and polarization transfer agents in spectroscopy and imaging. These applications require high stability towards reducing biological environments, as well as beneficial relaxation properties. While the latter is provided by spirocyclic groups on the nitroxide scaffold, such systems are not in themselves robust under reducing conditions. In this work, we introduce a strategy for stability enhancement through conformational tuning, where incorporating additional substituents on the nitroxide ring effects a shift towards highly stable closed spirocyclic conformations, as indicated by X-ray crystallography and DFT calculations. Closed spirocyclohexyl nitroxides exhibit a dramatically improved stability towards reduction by ascorbate, while maintaining long relaxation times in EPR spectroscopy. These findings have important implications for the future design of new nitroxide-based spin labels and imaging agents

Infectious risk stratification in multiple sclerosis patients receiving immunotherapy

The increasing number of potent treatments for multiple sclerosis warrants screening for infections. To investigate the prevalence of infections in two independent German patient cohorts with multiple sclerosis/neuromyelitis optica spectrum disorders (NMOSD), we performed a retrospective chart review study of multiple sclerosis/NMOSD patients who underwent testing for infections between 2014 and 2016. We show that 6 out of 80 tested patients (Dusseldorf cohort) and 2 out of 97 tested patients (Munster cohort) had a latent tuberculosis infection; total 3.95%, 95% CI: 2-8%. Our findings suggest that latent tuberculosis infection is frequent (>1%). Screening should be performed before embarking on immunomodulatory therapies to allow treatment and mitigation of the risk of a reactivation

Replication Data for: Conformational tuning improves the stability of spirocyclic nitroxides with long paramagnetic relaxation times

Nitroxides are widely used as probes and polarization transfer agents in spectroscopy and imaging.These applications require high stability towards reducing biological environments, as well as beneficial relaxation properties. Closed spirocyclohexyl nitroxides exhibit a dramatically improved stability towards reduction by ascorbate, while maintaining long relaxation times in EPR spectroscopy. This dataset contains raw files and analysis reports of 1HNMR, 13CNMR, HRMS, FTIR of all compounds synthesized for and used in work: Conformational tuning improves the stability of spirocyclic nitroxides with long paramagnetic relaxation times. Moreover, for nitroxides raw files of X-band CW-EPR spectra, kinetic runs based on CW-EPR spectra and Q-band EPR relaxation measurements are included. Dataset is completed with X-ray crystallography CIF files and reports

Vps37a regulates hepatic glucose production by controlling glucagon receptor localization to endosomes.

During mammalian energy homeostasis, the glucagon receptor (Gcgr) plays a key role in regulating both glucose and lipid metabolisms. However, the mechanisms by which these distinct signaling arms are differentially regulated remain poorly understood. Using a Cy5-glucagon agonist, we show that the endosomal protein Vps37a uncouples glucose production from lipid usage downstream of Gcgr signaling by altering intracellular receptor localization. Hepatocyte-specific knockdown of Vps37a causes an accumulation of Gcgr in endosomes, resulting in overactivation of the cAMP/PKA/p-Creb signaling pathway to gluconeogenesis without affecting β-oxidation. Shifting the receptor back to the plasma membrane rescues the differential signaling and highlights the importance of the spatiotemporal localization of Gcgr for its metabolic effects. Importantly, since Vps37a knockdown in animals fed with a high-fat diet leads to hyperglycemia, although its overexpression reduces blood glucose levels, these data reveal a contribution of endosomal signaling to metabolic diseases that could be exploited for treatments of type 2 diabetes

The myxobacterial antibiotic myxovalargin: Biosynthesis, structural revision, total synthesis and molecular characterization of ribosomal inhibition

Resistance of bacterial pathogens against antibiotics is declared by WHO as a major global health threat. As novel antibacterial agents are urgently needed, we re-assessed the broad-spectrum myxobacterial antibiotic myxovalargin and found it to be extremely potent against Mycobacterium tuberculosis. To ensure compound supply for further development we studied myxovalargin biosynthesis in detail enabling production via fermentation of a native producer. Feeding experiments as well as functional genomics analysis suggested a structural revision, which was eventually corroborated by development of a concise total synthesis. The ribosome was identified as the molecular target based on resistant mutant sequencing and a cryo-EM structure revealed that myxovalargin binds within and completely occludes the exit tunnel, consistent with a mode of action to arrest translation during a late stage of translation initiation. Pharmacokinetic and initial in vivo efficacy studies indicated that myxovalargin and analogues show potential for development as an antibacterial agent

Sunlight exposure exerts immunomodulatory effects to reduce multiple sclerosis severity

Multiple sclerosis (MS) disease risk is associated with reduced sunexposure. This study assessed the relationship between measures of sun exposure (vitamin D [vitD], latitude) and MS severity in the setting of two multicenter cohort studies (n(NationMS) = 946, n(BIONAT) = 990). Additionally, effect-modification by medication and photosensitivity-associated MC1R variants was assessed. High serum vitD was associated with a reduced MS severity score (MSSS), reduced risk for relapses, and lower disability accumulation over time. Low latitude was associated with higher vitD, lower MSSS, fewer gadolinium-enhancing lesions, and lower disability accumulation. The association of latitude with disability was lacking in IFN-beta-treated patients. In carriers of MC1R:rs1805008(T), who reported increased sensitivity toward sunlight, lower latitude was associated with higher MRI activity, whereas for noncarriers there was less MRI activity at lower latitudes. In a further exploratory approach, the effect of ultraviolet (UV)-phototherapy on the transcriptome of immune cells of MS patients was assessed using samples from an earlier study. Phototherapy induced a vitD and type I IFN signature that was most apparent in monocytes but that could also be detected in B and T cells. In summary, our study suggests benefidal effects of sun exposure on established MS, as demonstrated by a correlative network between the three factors: Latitude, vitD, and disease severity. However, sun exposure might be detrimental for photosensitive patients. Furthermore, a direct induction of type I IFNs through sun exposure could be another mechanism of UV-mediated immune-modulation in MS