Biology subjects

Kucera, L.

Publications and source records attributed to Kucera, L..

3 recordsLinked to original sources

bioRxiv2026

Multimodal Imaging Reveals Spatial Host-Pathogen Microenvironments in Escherichia coli Meningoencephalitis

Experimental bacterial meningitis is often analyzed as microbial burden and inflammation, but the tissue-level organization of host-pathogen interplay remains poorly resolved. Here, we use multimodal imaging to map Escherichia coli meningoencephalitis as a spatially organized process across infected rat brain tissue and cerebrospinal fluid (CSF). A low-dose intracerebral inoculum expands within 24 h into an anatomically structured infection involving ventricular, meningeal, and perivascular interfaces. Scanning electron microscopy reveals biofilm-like multicellular E. coli aggregates embedded in extracellular material, consistent with neutrophil extracellular traps. MALDI mass spectrometry imaging detects aerobactin and salmochelin-derived metabolites, whereas intact enterobactin is not detected despite favorable analytical sensitivity. These bacterial iron-acquisition signals partially overlap with calprotectin proteoforms, defining ventricular and periventricular metal-conflict microenvironments. Spatial peptidomics identifies infection-enriched antimicrobial territories dominated by rat neutrophil peptides RatNP-2, RatNP-3, and RatNP-4. Endogenous proenkephalin-derived neuropeptides are reduced in basal ganglia regions. Finally, cerebrospinal fluid captures both bacterial siderophores and host antimicrobial peptides with lipocalin-2 protein, linking tissue-resolved host-pathogen chemistry to a proximal diagnostic fluid. Together, these data show that experimental E. coli meningoencephalitis is a spatially organized host-pathogen process. Bacterial communities, nutritional immunity, antimicrobial peptides, and neuropeptide networks occupy distinct but connected CNS niches, components of which are recoverable in CSF.

neuroscience↗

bioRxiv2026

TRANSSULFURATION LINKS ASPARTATE-ASPARAGINE METABOLISM AND REDOX HOMEOSTASIS TO DRIVE TUMOR GROWTH

Cytosolic redox balance is tightly coupled to aspartate synthesis through the malate-aspartate shuttle, and limiting the malate-aspartate shuttle has been proposed to constrain tumor growth by restricting aspartate availability. Here we show that tumors derived from cancer cells lacking GOT1 and GOT2, the cytosolic and mitochondrial aspartate aminotransferases essential for as-partate production and malate-aspartate shuttle function, grow despite impaired canonical as-partate synthesis. This is because cytosolic redox state, not aspartate supply, is the primary metabolic bottleneck in GOT1/GOT2 knockout cells. Using single-cell transcriptomics, metabo-lite tracing, and a loss-of-function CRISPR screen, we find that these tumors engage an adaptive bypass in which availability of asparagine, a product of aspartate, enables serine- and methio-nine-dependent transsulfuration to generate -ketobutyrate, whose reduction regenerates cy-tosolic NAD and restores redox homeostasis. Pharmacological inhibition or genetic ablation of transsulfuration abrogates this asparagine-driven rescue. These findings define asparagine as a regulator of cytosolic NAD/NADH balance and reveal a link between amino acid metabolism and redox control that suggests transsulfuration as a targetable vulnerability in tumor redox maintenance. Significance statementAspartate synthesis and cytosolic redox balance are both coupled through the malate-aspartate shuttle. We show that the cytosolic NAD/NADH ratio, not aspartate supply, is a critical output of the malate-aspartate shuttle for tumor growth. Availability of asparagine, a product of aspar-tate, enables serine- and methionine-dependent transsulfuration to restore cytosolic NAD/NADH balance, proliferation and tumor growth independently of canonical aspartate pro-duction by the malate-aspartate shuttle. This defines asparagine as a regulator of cytosolic re-dox and identifies transsulfuration as a targetable vulnerability in tumor redox maintenance.

cancer biology↗

bioRxiv2021

A mixture of innate cryoprotectants is key for cryopreservation of a drosophilid fly larva.

Insects that naturally tolerate internal freezing produce complex mixtures of multiple cryoprotectants (CPs). Better knowledge on composition of these mixtures, and on mechanisms of how the individual CPs interact, could inspire development of laboratory CP formulations optimized for cryopreservation of cells and other biological material. Here we identify and quantify (using high resolution mass spectrometry) a range of putative CPs in larval tissues of a subarctic fly, Chymomyza costata that survives long-term cryopreservation in liquid nitrogen. The CPs (proline, trehalose, glutamine, asparagine, glycine betaine, glycerophosphoethanolamine, glycerophosphocholine, and sarcosine) accumulate in hemolymph in a ratio of 313:108:55:26:6:4:3:0.5 mmol.L-1. Using calorimetry, we show that the artificial mixtures, mimicking the concentrations of major CPs in hemolymph of freeze-tolerant larvae, suppress the melting point of water and significantly reduce the ice fraction. We demonstrate in a bioassay that mixtures of CPs administered through the diet act synergistically rather than additively to enable cryopreservation of otherwise freeze-sensitive larvae. Using MALDI-MSI, we show that during slow extracellular freezing trehalose becomes concentrated in partially dehydrated hemolymph where it stimulates transition to the amorphous glass phase. In contrast, proline moves to the boundary between extracellular ice and dehydrated hemolymph and tissues where it likely forms a layer of dense viscoelastic liquid. We propose that amorphous glass and viscoelastic liquids may protect macromolecules and cells from thermomechanical shocks associated with freezing and transfer into and out of liquid nitrogen. Summary statementThe composition of natural cryoprotectant mixture of the extremely freeze-tolerant insect is revealed. Components of the mixture work in synergy and behave differently during organismal freezing and cryopreservation.

physiology↗