Biology subjects

Schultz, K.

Publications and source records attributed to Schultz, K..

13 recordsLinked to original sources

bioRxiv2026

Electrical Stunning does not affect Brain Tissue Integrity and Stress Response in Larval Zebrafish

Electrical stunning is a humane euthanasia method for larval zebrafish, and a suitable euthanasia protocol has recently been established. Here, we assess the associated stress response and tissue integrity. When compared to MS-222 overdose and hypothermia, electrical stunning caused no significant Hsp70 increase. Brain tissue was preserved and muscle tissue affected only slightly. Our results support the suitability of electrical stunning for humane euthanasia and artifact-free post-mortem analyses.

systems biology↗

bioRxiv2026

A comprehensive reference database to support untargeted metabolomics in Pseuudomonas putida

Pseudomonas putida strain KT2440 is a crucial model organism for synthetic biology and bioengineering applications, yet there currently exists no comprehensive metabolomics database comparable to those available for other model organisms. This gap hinders the use of untargeted metabolomics for exploratory analyses in this system. We developed the P. putida metabolome reference database (PPMDB v1) to address this limitation by consolidating metabolite information from multiple sources and expanding coverage through computational predictions. The database was constructed by curating metabolites from BioCyc, BiGG, and other literature sources, then computationally expanding this collection using BioTransformer environmental transformation predictions to generate additional predicted metabolites. We enhanced the databases utility for molecular annotation in metabolomics studies by incorporating analytical properties including collision cross-sections, tandem mass spectra, and gas-phase infrared spectra. These analytical properties were gathered from existing measurement data or predicted using computational tools. We further augmented the database through inclusion of reaction information and pathway annotations, facilitating biological interpretation of metabolomics data. This publicly available resource fills a critical gap in P. putida research infrastructure, supporting metabolite annotation and biological interpretation in untargeted metabolomics studies and enabling in-depth exploratory analyses of this important synthetic biology platform at the molecular level. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/713193v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@c8828forg.highwire.dtl.DTLVardef@1f3a5c5org.highwire.dtl.DTLVardef@1084535org.highwire.dtl.DTLVardef@1f7ca4a_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2026

Quercetin and 6-Br_uercetin antioxidant properties and off target screening results advance glycosylated 6BrQ as a development candidate for Alzheimers disease

Quercetin is an abundant dietary flavonol with interesting in vitro properties that include substrate-selective positive allosteric modulation (PAM) of the activity of the receptor type protein tyrosine phosphatase D (PTPRD) and substantial antioxidant actions. Its in vivo activities include reducing incidence of Alzheimers disease (AD) and reducing AD neurofibrillary pathology in mouse models. Structure-activity studies have identified quercetin analogs with improved in vitro and in vivo properties, including the improved PTPRD PAM 6-bromoquercetin (6BrQ). However, there is no comparison of the antioxidant properties of 6BrQ to those of quercetin. There is no systematic screening for activities of quercetin or of 6BrQ using a panel of targets for most currently-used drugs. We now report that both quercetin and 6BrQ provide equivalent results in cyclic voltammetric and biochemical antioxidant assays. We also report that neither 10-7 M quercetin nor 6BrQ provides any significant (>50%) effects on any of the 104 assays in a Eurofins off-target screening panel. At 10-5 M, both quercetin and 6BrQ exert significant effects in assays for glycogen synthase kinase 3 (GSK3{beta}) as well as those for serotonin 5HT2B receptor, adenosine transport, adenosine A2A receptors, cyclooxygenases COX1 and COX2, phosphodiesterases PDE3A and 4D2 and PPAR gamma. These data extend prior characterization of quercetins biochemical effects, provide novel results for 6BrQ and support the likelihood that both quercetin and 6BrQ can a) directly inhibit GSK3, b) reduce GSK3 activities via enhancement of its dephosphorylation by PTPRD and c) display modest numbers of off target activities at high concentrations, several of which could conceivably contribute to anti-AD activities. These results advance bioavailable glycosylated prodrugs that can be metabolized to 6BrQ as developmental candidates for AD.

neuroscience↗

bioRxiv2025

RhizoGrid: Illuminating Spatial Rhizosphere Dynamics

The rhizosphere microbiome directly influences plant health and acclimation to extreme environments, yet plant-microbe interactions in the rhizosphere have proven complex and difficult to study. We present RhizoGrid, a new methodological framework that integrates a 3D-printed pot structure with spatial measurements of root structure, metabollite and taxonomy to detect links between metabolites and microbes along a soil-grown root system. The RhizoGrid identifies microhabitats hidden belowground. Using the food, forage, and bioenergy crop sorghum, we showcase how the RhizoGrid opens new frontiers for exploring the heterogeneity and complexity of interactions between root exudates and microbes in the rhizosphere.

systems biology↗

bioRxiv2025

Cryo-EM Structure of the Cyclase Domain and Evaluation of Substrate Channeling in a Bifunctional Class II Terpene Synthase

Copalyl diphosphate synthase from Penicillium verruculosum (PvCPS) is a bifunctional class II terpene synthase containing a prenyltransferase that produces geranylgeranyl diphosphate (GGPP) and a class II cyclase that utilizes GGPP as a substrate to generate the bicyclic diterpene copalyl diphosphate. The various stereoisomers of copalyl diphosphate establish the greater family of labdane natural products, many of which have environmental and medicinal impact. Understanding structure-function relationships in class II diterpene synthases is crucial for guiding protein engineering campaigns aimed at the generation of diverse bicyclic diterpene scaffolds. However, only a limited number of structures are available for class II cyclases from bacteria, plants, and humans, and no structures are available for a class II cyclase from a fungus. Further, bifunctional class II terpene synthases have not been investigated with regard to substrate channeling between the prenyltransferase and the cyclase. Here, we report the 2.9 [A]-resolution cryo-EM structure of the 63-kD class II cyclase domain from PvCPS. Comparisons with bacterial and plant copalyl diphosphate synthases reveal conserved residues that likely guide the formation of the bicyclic labdane core, but divergent catalytic dyads that mediate the final deprotonation step of catalysis. Substrate competition experiments reveal preferential GGPP transit from the PvCPS prenyltransferase to the cyclase, even when prepared as separate constructs. These results are consistent with a model in which transient prenyltransferase-cyclase association facilitates substrate channeling due to active site proximity.

biochemistry↗

bioRxiv2024

Blood draw site and blood matrix influence mineral assessment

Circulating mineral concentrations are used to assess nutritional status or as markers for clinical conditions, but the quality of these measurements depends on the methods used for blood processing. Since the procedures for measuring mineral levels in blood are not standardized, discrepancies in sampling may influence the analytical results. We previously reported that zinc content in blood samples showed significant variation depending on several pre-analytical variables selected during blood collection and processing. In this study, we extend our analysis to determine how other mineral levels might be affected by different blood draw sites (capillary or venous) or sample matrices (plasma or serum). Sequential capillary and venous blood samples were collected from a diverse cohort of sixty healthy adults and analyzed for multiple minerals using inductively coupled plasma- optical emission spectrometry. Calcium, copper, iron, and magnesium were the only minerals that were detected in all samples and were free from contamination in the blood collection tubes used for the study. When assessing different blood draw sites, the concentrations of calcium, copper, iron, and magnesium were 2-11% higher from capillary compared to the venous plasma. When assessing different blood sample matrices, the concentrations of calcium, copper, and magnesium were 2-5% higher in serum compared to plasma samples, whereas the concentration of iron was 7% higher in plasma compared to serum samples. The differences observed in these four essential minerals from discrepant draw sites and blood matrices demonstrate the importance of controlling key pre-analytic variables when assessing mineral levels in blood.

biochemistry↗

bioRxiv2024

Engineering Substrate Channeling in Assembly-Line Terpene Biosynthesis

Fusicoccadiene synthase from P. amygdala (PaFS) is a bifunctional assembly-line terpene synthase containing a prenyltransferase domain that generates geranylgeranyl diphosphate (GGPP) from dimethylallyl diphosphate (DMAPP) and three equivalents of isopentenyl diphosphate (IPP), and a cyclase domain that converts GGPP into fusicoccadiene, a precursor of the diterpene glycoside Fusicoccin A. The two catalytic domains are linked by a flexible 69-residue polypeptide segment. The prenyltransferase domain mediates oligomerization to form predominantly octamers, and cyclase domains are randomly splayed out around the prenyltransferase core. Previous studies suggest that substrate channeling is operative in catalysis, since most of the GGPP formed by the prenyltransferase remains on the protein for the cyclization reaction. Here, we demonstrate that the flexible linker is not required for substrate channeling, nor must the prenyltransferase and cyclase domains be covalently linked to sustain substrate channeling. Moreover, substrate competition experiments with other diterpene cyclases indicate that the PaFS prenyltransferase and cyclase domains are preferential partners regardless of whether they are covalently linked or not. The cryo-EM structure of engineered "linkerless" construct PaFSLL, in which the 69-residue linker is spliced out and replaced with the tripeptide PTQ, reveals that cyclase pairs associate with all four sides of the prenyltransferase octamer. Taken together, these results suggest that optimal substrate channeling is achieved when a cyclase domain associates with the side of the prenyltransferase octamer, regardless of whether the two domains are covalently linked and regardless of whether this interaction is transient or locked in place.

biochemistry↗

bioRxiv2023

Epigenetic changes and serotype-specific interferon-responses of lung epithelial cells in late post-influenza pneumococcal pneumonia

Pneumococcal infection following influenza A virus (IAV) pneumonia is a synergistic complication with high mortality. IAV modulates host antibacterial responses and invasiveness of pneumococcal serotypes and is an important pathogenic factor 2. Yet, serotype-specifc immediate-early responses of the IAV-perturbed alveolar epithelium have not been adressed. We analyzed gene transcription in alveolar type II epithelial cells (AECII) from mice infected with IAV and/or one of three S. pneumoniae (S.pn.) serotypes of varying invasiveness (4 > 7F > 19F). IAV, 14 days post infection, rendered the lung susceptible to invasive S.pn. infection with serotype 4 and the mildly invasive 7F but not 19F. Only 7F secondary infection induced exacerbated cytokine/chemokine responses. IAV/7F infection induced superior protein expression of type I and II interferons, exceeding that in IAV/serotype 4 infection. Inference of a scale-free-like ARACNE gene co-expression network revealed interferon-response network modules. Network-mapping unfolded S.pn. serotype-specific transcriptional network responses/usage. Secondary S.pn. infection abrogated the IAV-induced pneumocyte proliferative configuration and IAV infection rendered the transcriptional response to 7F comparable to that of serotype 4. This related to network genes correlating with the expression of two master regulators of interferon responses: Irf7 and Stat1. Epigenetic ATAC-seq analysis of AECII in resolved IAV infection identified enhanced expression of ARACNE network genes Hist1h2bf, Igtp, Mki67, Rasl10b, H2-Q6 and H2-Q7 to be associated with increased chromatin accessability at promoter regions. We show that AECII retain a sustained IAV-associated transcriptional configuration with epigenetic involvement that serotype-specifically affects proliferation and intensifies the AECII transcriptional response, mainly to interferons, in S.pn. infection.

immunology↗

bioRxiv2023

Semi-synthetic CoA-alpha-Synuclein Constructs Trap N-terminal Acetyltransferase NatB for Binding Mechanism Studies

N-terminal acetylation is a chemical modification carried out by N-terminal acetyltransferases (NATs). A major member of this enzyme family, NatB, acts on much of the human proteome, including -synuclein (S), a synaptic protein that mediates vesicle trafficking. NatB acetylation of S modulates its lipid vesicle binding properties and amyloid fibril formation, which underlies its role in the pathogenesis of Parkinsons disease. Although the molecular details of the interaction between human NatB (hNatB) and the N-terminus of S have been resolved, whether the remainder of the protein plays a role in interacting with the enzyme is unknown. Here we execute the first synthesis, by native chemical ligation, of a bisubstrate inhibitor of NatB consisting of coenzyme A and full-length human S, additionally incorporating two fluorescent probes for studies of conformational dynamics. We use cryo-electron microscopy (cryo-EM) to characterize the structural features of the hNatB/inhibitor complex and show that, beyond the first few residues, S remains disordered when in complex with hNatB. We further probe changes in the S conformation by single molecule Forster resonance energy transfer (smFRET) to reveal that the C-terminus expands when bound to hNatB. Computational models based on the cryo-EM and smFRET data help to explain the conformational changes and their implications for hNatB substrate recognition and specific inhibition of the interaction with S. Beyond the study of S and NatB, these experiments illustrate valuable strategies for the study of challenging structural biology targets through a combination of protein semi-synthesis, cryo-EM, smFRET, and computational modeling.

biochemistry↗

bioRxiv2023

Non-catalytic regulation of 18S rRNA methyltransferase DIMT1 in acute myeloid leukemia

Several rRNA modifying enzymes install rRNA modifications while participating in ribosome assembly. Here, we show that 18S rRNA methyltransferase DIMT1 is essential for acute myeloid leukemia (AML) proliferation through a non-catalytic function. We reveal that targeting a positively charged cleft of DIMT1, remote from the catalytic site, weakens the binding of DIMT1 to rRNA and mis-localizes DIMT1 to the nucleoplasm, in contrast with the primarily nucleolar localization of wild-type DIMT1. Mechanistically, rRNA binding is required for DIMT1 to undergo liquid-liquid phase separation, which explains why the distinct nucleoplasm localization of the rRNA-binding deficient DIMT1. Re-expression of wild-type or a catalytically inactive mutant E85A, but not the rRNA-binding deficient DIMT1, supports AML cell proliferation. This study provides a new strategy to target DIMT1-regulated AML proliferation via targeting this essential non-catalytic region.

molecular biology↗

bioRxiv2022

Tracking influenza a virus infection in the lung from hematological data with machine learning

The tracking of pathogen burden and host responses with minimal-invasive methods during respiratory infections is central for monitoring disease development and guiding treatment decisions. Utilizing a standardized murine model of respiratory Influenza A virus (IAV) infection, we developed and tested different supervised machine learning models to predict viral burden and immune response markers, i.e. cytokines and leukocytes in the lung, from hematological data. We performed independently in vivo infection experiments to acquire extensive data for training and testing purposes of the models. We show here that lung viral load, neutrophil counts, cytokines like IFN-{gamma} and IL-6, and other lung infection markers can be predicted from hematological data. Furthermore, feature analysis of the models shows that blood granulocytes and platelets play a crucial role in prediction and are highly involved in the immune response against IAV. The proposed in silico tools pave the path towards improved tracking and monitoring of influenza infections and possibly other respiratory infections based on minimal-invasively obtained hematological parameters.

microbiology↗

bioRxiv2021

A gut microbial metabolite of dietary polyphenols reverses obesity-driven hepatic steatosis

The molecular mechanisms by which dietary fruits and vegetables confer cardiometabolic benefits remain poorly understood. Historically, these beneficial properties have been attributed to the antioxidant activity of flavonoids. Here, we reveal that the host metabolic benefits associated with flavonoid consumption actually hinge on gut microbial metabolism. We show that a single gut microbial flavonoid catabolite is sufficient to reduce diet-induced cardiometabolic disease burden in mice. Dietary supplementation with elderberry extract attenuated obesity and continuous delivery of the catabolite 4-hydroxphenylacetic acid was sufficient to reverse hepatic steatosis. Analysis of human gut metagenomes revealed that under one percent contains a flavonol catabolic pathway, underscoring the rarity of this process. Our study will impact the design of dietary and probiotic interventions to complement traditional cardiometabolic treatment strategies. One-Sentence SummarySelect gut microbes can metabolize flavonoids from a fruit and vegetable diet to monophenolic acids, which improve fatty liver disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/460661v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1c4f56borg.highwire.dtl.DTLVardef@1cc4be3org.highwire.dtl.DTLVardef@18a4af5org.highwire.dtl.DTLVardef@3f44a5_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Influenza A virus (H1N1) infection induces microglia activation and temporal dysbalance in glutamatergic synaptic transmission.

3.Influenza A virus (IAV) causes respiratory tract disease and is responsible for seasonal and reoccurring epidemics affecting all age groups. Next to typical disease symptoms such as fever and fatigue, IAV infection has been associated with behavioral alterations presumably contributing to the development of major depression. Previous experiments using IAV/H1N1 infection models have shown impaired hippocampal neuronal morphology and cognitive abilities, but the underlying pathways have not been fully described. In this study, we demonstrate that infection with a low dose non-neurotrophic H1N1 strain of IAV causes ample peripheral immune response followed by a temporary blood-brain-barrier disturbance. Although histological examination did not reveal obvious pathological processes in the brains of IAV-infected mice, detailed multidimensional flow cytometric characterization of immune cells uncovered subtle alterations in the activation status of microglia cells. More specifically, we detected an altered expression pattern of major histocompatibility complex class I and II, CD80, and F4/80 accompanied by elevated mRNA levels of CD36, CD68, C1QA, and C3, suggesting evolved synaptic pruning. To closer evaluate how these profound changes affect synaptic balance, we established a highly sensitive multiplex flow cytometry-based approach called Flow Synaptometry. The introduction of this novel technique enabled us to simultaneously quantify the abundance of pre- and postsynapses from distinct brain regions. Our data reveal a significant reduction of VGLUT1 in excitatory presynaptic terminals in the Cortex and Hippocampus, identifying a subtle dysbalance in glutamatergic synapse transmission upon H1N1 infection in mice. In conclusion, our results highlight the consequences of systemic IAV-triggered inflammation on the central nervous system and the induction and progression of neuronal alterations.

immunology↗