Biology subjects

Klatt, S.

Publications and source records attributed to Klatt, S..

5 recordsLinked to original sources

bioRxiv2024

The transaminase-omega-amidase pathway is a redox switch in glutamine metabolism that generates alpha-ketoglutarate

Oxidative stress is caused by short-lived molecules and metabolic changes belong to the fastest cellular responses. Here we studied how the endothelial cell metabolome reacts to acute oxidative challenges (menadione or H2O2) to identify redox-sensitive metabolic enzymes. H2O2 selectively increased -ketoglutaramate (KGM), a largely uncharacterized metabolite produced by glutamine transamination and a yet unrecognized intermediate of endothelial glutamine catabolism. The enzyme nitrilase-like 2 {omega}-amidase (NIT2) converts KGM to -ketoglutarate (KG). Reversible oxidation of specific cysteine in NIT2 by H2O2 inhibited its catalytic activity. Furthermore, a variant in the NIT2 gene that decreases its expression is associated with high plasma KGM level in humans. Endothelial-specific knockout mice of NIT2 exhibited increased levels of KGM and impaired angiogenesis. Knockout of NIT2 impaired endothelial cell proliferation and sprouting and induced senescence. In conclusion, we show that the glutamine transaminase-{omega}-amidase pathway is a metabolic switch in which NIT2 is the redox-sensitive enzyme. The pathway is modulated in humans and functionally important for endothelial glutamine metabolism.

physiology↗

bioRxiv2024

Metabolic alterations drive inflammatory phenotypes in CHIP-associated heart failure

Mutations in DNA methyltransferase 3 alpha (DNMT3A) are the most frequent driver of clonal hematopoiesis of indeterminate potential (CHIP), and associated with higher risk of cardiovascular disease and pro-inflammatory activation of immune cells. Here, we investigated the mechanisms underlying DNMT3A CHIP-associated inflammatory phenotypes in macrophages. We show that monocytes of DNMT3A CHIP-driver mutation carriers are associated with DNA hypomethylation of succinate dehydrogenase A (SDHA) and an altered tricarboxylic acid cycle metabolite profile. Silencing of DNMT3A in monocytes increased SDHA and elevated mitochondria complex II activity. The secreted complex II product, malate, further increased inflammatory activation in wild type monocytes to further augment inflammation in a paracrine manner. Pharmacological inhibition of SDHA (using dimethyl malonate) in mice harboring DNMT3A mutations in hematopoietic stem cells ameliorated the inflammatory response and improved cardiac function after myocardial infarction. Thus, interfering with the altered metabolic state may provide a new therapeutic option to dampen inflammatory activation in DNMT3A CHIP carrying patients.

molecular biology↗

bioRxiv2024

A marine sponge-associated mycobacterium closely related to Mycobacterium tuberculosis

Reconstructing the evolutionary origins of Mycobacterium tuberculosis, the causative agent of human tuberculosis, has helped identify bacterial factors that have led to the tubercle bacillus becoming such a formidable human pathogen. Here we report the discovery and detailed characterization of an exceedingly slow growing mycobacterium that is closely related to M. tuberculosis for which we have proposed the species name Mycobacterium spongiae sp. nov., (strain ID: FSD4b-SM). The bacterium was isolated from a marine sponge, taken from the waters of the Great Barrier Reef in Queensland, Australia. Comparative genomics revealed that, after the opportunistic human pathogen Mycobacterium decipiens, M. spongiae is the most closely related species to the M. tuberculosis complex reported to date, with 80% shared average nucleotide identity and extensive conservation of key M. tuberculosis virulence factors, including intact ESX secretion systems and associated effectors. Proteomic and lipidomic analyses showed that these conserved systems are functional in FSD4b-SM, but that it also produces cell wall lipids not previously reported in mycobacteria. We investigated the virulence potential of FSD4b-SM in mice and found that, while the bacteria persist in lungs for 56 days after intranasal infection, no overt pathology was detected. The similarities with M. tuberculosis, together with its lack of virulence, motivated us to investigate the potential of FSD4b-SM as a vaccine strain and as a genetic donor of the ESX-1 genetic locus to improve BCG immunogenicity. However, neither of these approaches resulted in superior protection against M. tuberculosis challenge compared to BCG vaccination alone. The discovery of M. spongiae adds to our understanding of the emergence of the M. tuberculosis complex and it will be another useful resource to refine our understanding of the factors that shaped the evolution and pathogenesis of M. tuberculosis.

microbiology↗

bioRxiv2023

Age-dependent RGS5 loss in pericytes induces cardiac dysfunction and fibrosis in the heart

BackgroundPericytes are capillary-associated mural cells involved in the maintenance and stability of the vascular network. Although ageing is one of the main risk factors for cardiovascular disease, the consequences of ageing on cardiac pericytes are unknown. MethodsIn this study, we have combined single-nucleus RNA sequencing and histological analysis to determine the effects of ageing on cardiac pericytes. Furthermore, we have conducted in vivo and in vitro analysis of Regulator of G protein signalling 5 (RGS5) loss of function and finally have performed pericytes-fibroblasts co-culture studies to understand the effect of RGS5 deletion in pericytes on the neighbouring fibroblasts. ResultsAgeing reduced the pericyte area and capillary coverage in the murine heart. Single nucleus RNA sequencing analysis further revealed that the expression of Rgs5 was reduced in cardiac pericytes from aged mice. In vivo and in vitro studies showed that the deletion of RGS5 impaired cardiac function, fibrosis, and induced morphological changes and a pro-fibrotic gene expression signature in pericytes characterized by the expression of different extracellular matrix components and growth factors e.g. TGFB2 and PDGFB. Indeed, culturing fibroblasts with the supernatant of RGS5 deficient pericytes induced their activation as evidenced by the increased expression of smooth muscle actin in a TGF{beta}2-dependent mechanism. ConclusionsOur results have identified RGS5 as a crucial regulator of pericyte function during cardiac ageing. The deletion of RGS5 causes cardiac dysfunction and induces myocardial fibrosis, one of the hallmarks of cardiac ageing.

physiology↗

bioRxiv2023

The WalKR two-component regulator coordinates cell wall homeostasis with DNA replication in Staphylococcus aureus

Among the 16 two-component systems (TCSs) in the opportunistic human pathogen Staphylococcus aureus, only WalKR is essential. Like orthologous systems in other Bacillota, S. aureus WalKR controls autolysins involved in peptidoglycan remodelling and is therefore intimately involved in cell division. However, despite the importance of WalKR in S. aureus, the basis for its essentiality is not understood and the regulon poorly defined. Here, we defined a consensus WalR DNA-binding motif and the direct WalKR regulon by using functional genomics, including ChIP-seq, with a panel of isogenic walKR mutants that had a spectrum of altered activities. Consistent with prior findings, the direct regulon includes multiple autolysin genes. However, this work also revealed that WalR directly regulates at least five essential genes involved in lipoteichoic acid synthesis (ltaS); translation (rplK); DNA compaction (hup); initiation of DNA replication (dnaA, hup); and purine nucleotide metabolism (prs). Thus, WalKR in S. aureus serves as a polyfunctional regulator that contributes to fundamental control over critical cell processes by co-ordinately linking cell wall homeostasis with purine biosynthesis, protein biosynthesis, and DNA replication. Collectively, our findings address the essentiality of this locus and highlight the importance of WalKR as a bona fide target for novel anti-staphylococcal therapeutics.

microbiology↗