Biology subjects

Spengler, B.

Publications and source records attributed to Spengler, B..

8 recordsLinked to original sources

bioRxiv2024

Sleep pressure accumulates in a voltage-gated lipid peroxidation memory

Voltage-gated potassium (KV) channels contain cytoplasmic {beta}-subunits whose aldo-keto reductase activity is required for the homeostatic regulation of sleep. Here we show that Hyperkinetic, the {beta}-subunit of the KV1 channel Shaker in Drosophila, forms a dynamic lipid peroxidation memory. Information is stored in the oxidation state of Hyperkinetics nicotinamide adenine dinucleotide phosphate (NADPH) cofactor, which changes when lipid-derived carbonyls, such as 4-oxo-2-nonenal or an endogenous analog generated by illuminating a membrane-bound photosensitizer, abstract an electron pair. NADP+ remains locked in the active site of KV{beta} until membrane depolarization permits its release and replacement with NADPH. Sleep-inducing neurons use this voltage-gated oxidoreductase cycle to encode their recent lipid peroxidation history in the collective binary states of their KV{beta}-subunits; this biochemical memory influences--and is erased by--spike discharges driving sleep. The presence of a lipid peroxidation sensor at the core of homeostatic sleep control suggests that sleep protects neuronal membranes against oxidative damage. Indeed, brain phospholipids are depleted of vulnerable polyunsaturated fatty acyl chains after enforced waking, and slowing the removal of their carbonylic breakdown products increases the demand for sleep.

neuroscience↗

bioRxiv2024

Large-Scale Evaluation of Spatial Metabolomics Protocols and Technologies

Spatial metabolomics using imaging mass spectrometry (MS) enables untargeted and label-free metabolite mapping in biological samples. Despite the range of available imaging MS protocols and technologies, our understanding of metabolite detection under specific conditions is limited due to sparse empirical data and predictive theories. Consequently, challenges persist in designing new experiments, and accurately annotating and interpreting data. In this study, we systematically measured the detectability of 172 biologically-relevant metabolites across common imaging MS protocols using custom reference samples. We evaluated 24 MALDI-imaging MS protocols for untargeted metabolomics, and demonstrated the applicability of our findings to complex biological samples through comparison with animal tissue data. We showcased the potential for extending our results to further analytes by predicting metabolite detectability based on molecular properties. Additionally, our interlaboratory comparison of 10 imaging MS technologies, including MALDI, DESI, and IR-MALDESI, showed extensive metabolite coverage and comparable results, underscoring the broad applicability of our findings within the imaging MS community. We share our results and data through a new interactive web application integrated with METASPACE. This resource offers an extensive catalogue of detectable metabolite ions, facilitating protocol selection, supporting data annotation, and benefiting future untargeted spatial metabolomics studies.

systems biology↗

bioRxiv2023

Lipid signatures and inter-cellular heterogeneity of naive and lipopolysaccharide-stimulated human microglia-like cells

Microglia are non-neuronal cells, which are residing in the central nervous system and are known to play an important role in health and disease. We investigated lipidomic phenotypes of human naive and stimulated microglia-like cells by atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI). With lateral resolutions between 5 m and 1.5 m, we were able to chart lipid compositions of individual cells, enabling to differentiate cell lines and stimulation conditions. This allowed us to reveal local lipid heterogeneities in naive and lipopolysaccharide (LPS)-stimulated cells. We were able to identify individual cells with elevated triglyceride (TG) levels and could show that the number of these TG-enriched cells increased with LPS stimulation as a hallmark for a proinflammatory phenotype. Additionally, observed local abundance alterations of specific phosphatidylinositols (PIs) indicate a cell specific regulation of the PI metabolism.

biochemistry↗

bioRxiv2022

A key regulator with a MIF-like domain orchestrates cellular differentiation and virulence in the fungal pathogen Magnaporthe oryzae

MACROPHAGE MIGRATION INHIBITORY FACTOR (MIF) is a pleiotropic protein with chemotactic, pro-inflammatory, and growth-promoting activities first discovered in mammals. In parasites, MIF homologs are involved in immune evasion and pathogenesis. Here, we present the first comprehensive analysis of a MIF protein from the devastating plant pathogen Magnaporthe oryzae (Mo). The fungal genome encodes a single MIF protein (MoMIF1) that, unlike the human homolog, harbors multiple low-complexity regions (LCRs) and is unique to Ascomycota. Following infection, MoMIF1 is expressed in the biotrophic phase of the fungus, and is strongly down-regulated during subsequent necrotrophic growth in leaves and roots. We show that MoMIF1 is secreted during plant infection, affects the production of the mycotoxin tenuazonic acid and inhibits plant cell death. Our results show that MoMIF1 is a novel key regulator of fungal virulence that maintains the balance between biotrophy and necrotrophy during the different phases of fungal infection.

plant biology↗

bioRxiv2022

Spatial metabolomics reveal divergent cardenolide processing in the monarch butterfly (Danaus plexippus) and the common crow (Euploea core)

Although being famous for sequestering milkweed cardenolides, the mechanism of sequestration and where cardenolides are localized in caterpillars of the monarch butterfly (Danaus plexippus) is still unknown. While monarchs tolerate cardenolides by a resistant Na+/K+-ATPase, it is unclear how closely related species such as the non-sequestering common crow (Euploea core) cope with these toxins. Using novel atmospheric-pressure scanning microprobe matrix-assisted laser/desorption ionization mass spectrometry imaging, we compared the distribution of cardenolides in caterpillars of D. plexippus and E. core. Specifically, we tested at which physiological scale quantitative differences between both species are mediated and how cardenolides distribute across body tissues. Whereas D. plexippus sequestered most cardenolides from milkweed (Asclepias curassavica), no cardenolides were found in the tissues of E. core. Remarkably, quantitative differences already manifest in the gut lumen: while monarchs retain and accumulate cardenolides above plant concentrations, the toxins are degraded in the gut lumen of crows. We visualized cardenolide transport over the monarch midgut epithelium and identified integument cells as the final site of storage where defenses might be perceived by predators. Our study provides molecular insight into cardenolide sequestration and highlights the great potential of mass spectrometry imaging for understanding the kinetics of multiple compounds including endogenous metabolites, plant toxins, or insecticides in insects.

ecology↗

bioRxiv2021

Sphingolipid Control of Fibroblast Heterogeneity Revealed by Single-Cell Lipidomics

Human cells produce thousands of lipids that impact a wide range of biological processes in ways we are only starting to characterize. The cellular composition in lipids changes during differentiation events and also varies across individual cells of the same type. Yet, the precise differences in lipid composition that directly affect cell phenotypes remain unknown. Here we have measured the lipidomes and transcriptomes of individual human dermal fibroblasts by coupling high-resolution mass spectrometry imaging to single-cell transcriptomics. We found that the cell-to-cell variation of specific lipid metabolic pathways contributes to the establishment of cell states involved in wound repair and in skin cancer growth. Sphingolipid composition defined fibroblast subpopulations while sphingolipid metabolic rewiring drove cell state transitions. These data uncover a role for cell-to-cell lipid heterogeneity in the determination of cell states and reveal a new regulatory component to the homeostasis and self-organization of multicellular systems.

biochemistry↗

bioRxiv2020

Host-induced gene silencing involves transfer of dsRNA-derived siRNA via extracellular vesicles

Small (s)RNAs and their double-stranded (ds)RNA precursors have been adopted to control diseases in crop plants through expression in transgenic plants and targeted gene silencing (host-induced gene silencing, HIGS). While HIGS strategies proved to be effective, the mechanism of RNA transfer at the plant - pathogen interface is widely unknown. Here we show that extracellular vesicles (EVs) purified from Arabidopsis thaliana plants expressing CYP3RNA, a dsRNA originally designed to target the three CYP51 genes of the fungal pathogen Fusarium graminearum, contain CYP3RNA-derived small interfering (si)RNAs as shown by RNA sequencing (RNA-seq) analysis. These transgene specific siRNAs had a length of 21 and 22 nucleotides with a bias towards 5-uracil (U) and 5-adenine (A). Notably, stringent protease and RNase treated EV fractions contained >70% less CYP3RNA-derived siRNAs, suggesting the presence of co-purified extravesicular nucleoprotein complexes stabilizing siRNAs outside of EVs. In addition, mutants of the ESCRT-III complex showed a loss of HIGS-mediated disease resistance and EVs isolated from these mutants were free of CYP3RNA-derived siRNAs. Together, these findings support the view that endosomal vesicle trafficking is required for HIGS mediating the transfer of transgene-derived siRNAs between donor host cells and recipient fungal cells probably in an EV-independent manner.

plant biology↗

bioRxiv2019

Spatial metabolomics of in situ, host-microbe interactions

Spatial metabolomics describes the location and chemistry of small molecules involved in metabolic phenotypes, defense molecules and chemical interactions in natural communities. Most current techniques are unable to spatially link the genotype and metabolic phenotype of microorganisms in situ at a scale relevant to microbial interactions. Here, we present a spatial metabolomics pipeline (metaFISH) that combines fluorescence in situ hybridization (FISH) microscopy and high-resolution atmospheric pressure mass spectrometry imaging (AP-MALDI-MSI) to image host-microbe symbioses and their metabolic interactions. metaFISH aligns and integrates metabolite and fluorescent images at the micrometer-scale for a spatial assignment of host and symbiont metabolites on the same tissue section. To illustrate the advantages of metaFISH, we mapped the spatial metabolome of a deep-sea mussel and its intracellular symbiotic bacteria at the scale of individual epithelial host cells. Our analytical pipeline revealed metabolic adaptations of the epithelial cells to the intracellular symbionts, a variation in metabolic phenotypes in one symbiont type, and novel symbiosis metabolites. metaFISH provides a culture-independent approach to link metabolic phenotypes to community members in situ - a powerful tool for microbiologists across fields.

microbiology↗