Biology subjects

Fischer, M. A.

Publications and source records attributed to Fischer, M. A..

8 recordsLinked to original sources

bioRxiv2026

Epithelial and γδ T cell CD47 have complementary yet distinct roles in regulating γδ intraepithelial lymphocyte migration

Intraepithelial lymphocytes expressing the {gamma}{delta} T cell receptor ({gamma}{delta} IEL) continuously survey the intestinal epithelium to promote mucosal host defense. Although {gamma}{delta} IELs migrate in and out of the lateral intercellular space (LIS) between adjacent enterocytes, the molecular mechanisms governing their migratory behavior are incompletely understood. Based on the known role of CD47, or integrin associated protein (IAP), in mediating neutrophil transepithelial migration, we investigated whether CD47 expression reflects a conserved mechanism regulating {gamma}{delta} IEL surveillance behavior. Here, we report that conditional CD47 deletion on intestinal epithelial cells or {gamma}{delta} T cells had no effect on IEL composition. Using intravital imaging, we identified complementary roles for CD47 on {gamma}{delta} IELs and epithelial cells, with epithelial CD47 restricting {gamma}{delta} IEL motility and {gamma}{delta} T-cell-derived CD47 promoting cell migration. Further investigation revealed that both CD47 and CD18 contribute to {gamma}{delta} IEL surveillance behavior, although CD47 regulates {gamma}{delta} IEL migration in a CD18-independent manner.

immunology↗

bioRxiv2024

Rapid onset fibrotic remodeling and ventricular dysfunction induced by phenylephrine involve targeted reprogramming of myocyte and fibroblast transcriptomes

Catecholamine dysregulation is a common feature of multiple acute and chronic cardiac conditions, including heart failure. To investigate the role of altered -adrenergic stimulation on cardiac function, we developed a short-term exposure model, administering phenylephrine subcutaneously to mice for one week. Compared to vehicle-injected controls, phenylephrine-treated animals exhibited increased ejection fraction, decreased chamber size, diastolic dysfunction and ventricular hypertrophy in the absence of hypertension. Remarkably, these animals developed extensive fibrotic remodeling of the tissue that plateaued at 24 hours and myocyte hypertrophy localized to regions of fibrotic deposition after 3 days of treatment. Transcriptome analyses of purified myocyte and fibroblast populations from these hearts revealed an unexpected role for myocytes in the production of extracellular matrix. Comparison with other models of cardiac stress, including pressure overload hypertrophy and cytokine activation of fibroblasts, identified stimulus-specific transcriptional circuits associated with cardiac pathology. Given the rapid, robust fibrotic response that preceded myocyte hypertrophy, intercellular communication analyses were conducted to investigate fibroblast to myocyte signaling, identifying potential crosstalk between these cells. These studies thoroughly describe and phenotypically characterize a new model of short-term catecholamine stress and provide an atlas of transcriptional remodeling in myocytes and fibroblasts. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=187 SRC="FIGDIR/small/617933v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@1e504faorg.highwire.dtl.DTLVardef@a9d5c1org.highwire.dtl.DTLVardef@10809aorg.highwire.dtl.DTLVardef@16b288d_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Type I interferon induces TCR-dependent and -independent antimicrobial responses in γδ intraepithelial lymphocytes

Intraepithelial lymphocytes (IEL) expressing the {gamma}{delta} T cell receptor (TCR) survey the intestinal epithelium to limit the invasion of microbial pathogens. The production of type I interferon (IFN) is a central component of an antiviral immune response, yet how these pro-inflammatory cytokines contribute to {gamma}{delta} IEL effector function remains unclear. Based on the unique activation status of IELs, and their ability to bridge innate and adaptive immunity, we investigated the extent to which type I IFN signaling modulates {gamma}{delta} IEL function. Using an ex vivo culture model, we find that type I IFN alone is unable to drive IFN{gamma} production, yet low level TCR activation synergizes with type I IFN to induce IFN{gamma} production in murine {gamma}{delta} IELs. Further investigation into the underlying molecular mechanisms of co-stimulation revealed that TCR{gamma}{delta}-mediated activation of NFAT and JNK is required for type I IFN to promote IFN{gamma} expression in a STAT4- dependent manner. Whereas type I IFN rapidly upregulates antiviral gene expression independent of a basal TCR{gamma}{delta} signal, neither tonic TCR triggering nor the presence of a TCR agonist was sufficient to elicit type I IFN-induced IFN{gamma} production in vivo. However, bypassing proximal TCR signaling events synergized with IFNAR/STAT4 activation to induce {gamma}{delta} IEL IFN{gamma} production. These findings indicate that {gamma}{delta} IELs contribute to host defense in response to type I IFN by mounting a rapid antimicrobial response independent of TCR{gamma}{delta} signaling, and under permissive conditions, produce IFN{gamma} in a TCR-dependent manner.

immunology↗

bioRxiv2024

Decreased Left Atrial Cardiomyocyte FGF13 Expression Increases Vulnerability to Postoperative Atrial Fibrillation in Humans

Postoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery and a significant cause of increased morbidity and mortality. The development of novel POAF therapeutics has been limited by an insufficient understanding of molecular mechanisms promoting atrial fibrillation. In this observational cohort study, we enrolled 28 patients without a history of atrial fibrillation that underwent mitral valve surgery for degenerative mitral regurgitation and obtained left atrial tissue samples along the standard atriotomy incision in proximity to the right pulmonary veins. We isolated cardiomyocytes and performed transcriptome analyses demonstrating 13 differentially expressed genes associated with new-onset POAF. Notably, decreased expression of fibroblast growth factor 13 (FGF13), a fibroblast growth factor homologous factor known to modulate voltage-gated sodium channel NaV1.5 inactivation, had the most significant association with POAF. To assess the functional significance of decreased FGF13 expression in atrial myocytes, we performed patch clamp experiments on neonatal rat atrial myocytes after siRNA-mediated FGF13 knockdown, demonstrating action potential prolongation. These critical findings indicate that decreased FGF13 expression promotes vulnerability to POAF.

genomics↗

bioRxiv2023

Novel hydroxamic acid derivative induces apoptosis and constrains autophagy in leukemic cells

IntroductionPosttranslational modification of proteins by reversible acetylation regulates key biological processes. Histone deacetylases (HDACs) catalyze protein deacetylation and are frequently dysregulated in tumors. This has spurred the development of HDAC inhibitors (HDACi). Such epigenetic drugs modulate protein acetylation, eliminate tumor cells, and are approved for the treatment of blood cancers. ObjectivesWe aimed to identify novel, nanomolar HDACi with increased potency over existing agents and selectivity for the cancer-relevant class I HDACs (HDAC1/-2/-3/-8). Moreover, we wanted to define how such drugs control the apoptosis-autophagy interplay. As test systems, we used human leukemic cells and embryonic kidney-derived cells. MethodsWe synthesized novel pyrimidine-hydroxamic acid HDACi (KH9/KH16/KH29) and performed in vitro activity assays and molecular modeling of their direct binding to HDACs. We analyzed how these HDACi affect leukemic cell fate, acetylation, and protein expression with flow cytometry and immunoblot. The publicly available DepMap database of CRISPR-Cas9 screenings was used to determine sensitivity factors across human leukemic cells. ResultsNovel HDACi show nanomolar activity against class I HDACs. These agents are superior to the clinically used hydroxamic acid HDACi vorinostat. Within the KH-series of compounds, KH16 (yanostat) is the most effective inhibitor of HDAC3 (IC50 = 6 nM) and the most potent inducer of apoptosis (IC50 = 110 nM; p<0.0001) in leukemic cells. KH16 though spares embryonic kidney-derived cells. Global data analyses of knockout screenings verify that HDAC3 is a dependency factor in human blood cancer cells of different lineages, independent of mutations in the tumor suppressor p53. KH16 alters pro- and anti-apoptotic protein expression, stalls cell cycle progression, and induces a caspase-dependent processing of the autophagy proteins ULK1 and p62. ConclusionThese data reveal that HDACs are required to stabilize autophagy proteins through a suppression of apoptosis in leukemic cells. HDAC3 appears as a valid anti-cancer target for pharmacological intervention. HighlightsO_LINovel HDACi with nanomolar activity against leukemic cells were synthesized. C_LIO_LIHDACi of the KH-series are superior to a clinical grade HDACi. C_LIO_LIHDACi of the KH-series modulate acetylation and phosphorylation of proteins. C_LIO_LIThe new HDACi KH16 regulates cell cycle arrest, apoptosis, and autophagy. C_LIO_LIApoptosis acts upstream of autophagy in KH16-treated cells. C_LI

pharmacology and toxicology↗

bioRxiv2022

Listeria monocytogenes gene essentiality under laboratory conditions and during macrophage infection

The Gram-positive bacterium Listeria monocytogenes occurs widespread in the environment and infects humans when ingested along with contaminated food. Such infections are particularly dangerous for risk group patients, for whom they represent a life-threatening disease. To invent novel strategies to control contamination and disease, it is important to identify those cellular processes that maintain pathogen growth in- and outside the host. We here have applied transposon insertion sequencing (Tn-Seq) to L. monocytogenes for the identification of such processes on a genome-wide scale. Our approach classified 394 open reading frames as essential for growth under standard laboratory conditions and identified 42 further genes, which become additionally essential during intracellular growth in macrophages. Most essential genes encode components of the translation machinery, act in chromosome-related processes, cell division and biosynthesis of the cellular envelope. Several cofactor biosynthesis pathways and 29 genes with unknown functions were also essential, opening novel options for the development of anti- listerial drugs. Among the genes specifically required during intracellular growth were known virulence factors, genes compensating intracellular auxotrophies and several cell division genes. Our experiments also highlight the importance of PASTA kinase signalling, glycine metabolism and chromosome segregation for efficient intracellular growth of L. monocytogenes.

microbiology↗

bioRxiv2020

MCL1 dependence across MDS subtypes and dual inhibition of MCL1 and BCL2 in MISTRG6 mice

Treatment for myelodysplastic syndromes (MDS) remains insufficient due to clonal heterogeneity and clinical complexity. Dysregulation of apoptosis is observed across MDS subtypes regardless of mutations and represents an attractive therapeutic opportunity. Venetoclax (VEN), a selective inhibitor of anti-apoptotic protein B-cell lymphoma-2 (BCL2), has yielded impressive responses in older patients with acute myeloid leukemia (AML). BCL2 family anti-apoptotic proteins BCL-XL and induced myeloid cell leukemia 1 (MCL1) are implicated in leukemia survival, and upregulation of MCL1 is seen in VEN-resistant AML and MDS. Here, we determined the in vitro sensitivity of MDS patient samples to selective inhibitors of BCL2, BCL-XL and MCL1. While VEN response positively correlated with increasing blast counts, all MDS subtypes responded to the MCL1 inhibitor, S63845. Treatment with combined VEN+S63845 was synergistic in all MDS subtypes and reduced MDS engraftment in MISTRG6 mice supporting the pursuit of clinical trials with combined BCL2+MCL1 inhibition in MDS.

cancer biology↗

bioRxiv2020

Population structure-guided profiling of antibiotic resistance patterns in clinical Listeria monocytogenes isolates from Germany identifies pbpB3 alleles associated with low levels of cephalosporin resistance

AO_SCPLOWBSTRACTC_SCPLOWCase numbers of listeriosis have been increasing in Germany and the European Union during the last decade. In addition reports on the occurrence of antibiotic resistance in Listeria monocytogenes in clinical and environmental isolates are accumulating. The susceptibility towards 14 antibiotics was tested in a selection of clinical L. monocytogenes isolates to get a more precise picture of the development and manifestation of antibiotic resistance in the L. monocytogenes population. Based on the population structure determined by core genome multi locus sequence typing (cgMLST) 544 out of 1,220 sequenced strains collected in Germany between 2009 and 2019 were selected to cover the phylogenetic diversity observed in the clinical L. monocytogenes population. All isolates tested were susceptible towards ampicillin, penicillin and co-trimoxazole - the most relevant antibiotics in the treatment of listeriosis. Resistance to daptomycin and ciprofloxacin was observed in 493 (91%) and in 71 (13%) of 544 isolates, respectively. While all tested strains showed resistance towards ceftriaxone, the minimal inhibitory concentrations (MIC) observed varied widely between 4 mg/L up to >128 mg/L. An allelic variation of the penicillin binding protein gene pbpB3 could be identified as the cause of this difference in ceftriaxone resistance levels. This study is the first population structure-guided analysis of antimicrobial resistance in recent clinical isolates and confirms the importance of penicillin binding protein B3 (PBP B3) for the high level of intrinsic cephalosporin resistance of L. monocytogenes on a population-wide scale.

microbiology↗