Biology subjects

Gallagher, P.

Publications and source records attributed to Gallagher, P..

4 recordsLinked to original sources

bioRxiv2026

Colistin resistance-mediated lipopolysaccharide modification in Klebsiella pneumoniae modulates host inflammatory response

Resistance to the polymyxin antimicrobial colistin in Gram-negative bacteria is associated with a modification of the immunogenic lipid A moiety of the lipopolysaccharide (LPS). Chromosomal and plasmid-borne colistin resistance results in the addition of L-Ara4N and pEtN groups to lipopolysaccharide (LPS), respectively. Here, using THP-1 cells, we studied the impact of different LPS modifications of Klebsiella pneumoniae in stimulating host immune response. K. pneumoniae clinical isolates were screened for colistin resistance using broth microdilution (BMD) and the MALDIxin test. LPS was extracted from colistin-resistant isolates and used to stimulate differentiated THP-1 cells. Luminex cytokine assay measured the immune induction via a panel of proinflammatory cytokines. Out of a collection of 72 clinical K. pneumoniae, eight (11.1%) exhibited phenotypic colistin resistance with a minimum inhibitory concentration (MIC) of 8 to 64 mg/L. In total, five isolates possessed genes associated with polymyxin resistance; three isolates had a mutation in the pmrB gene, and two were mcr-8.1 positive. MALDIxin demonstrated that all eight phenotypic colistin-resistant isolates elaborated peaks at m/z 1,955 and m/z 2,193, indicating an L-Ara4N group of LPS modification. For two mcr-8.1 positive isolates, LPS had a pEtN group. The LPS modification positively correlated with colistin MIC (correlation coefficient, r= 0.6 and R2= 0.4). Compared to the native structure, LPS modification was associated with greater production of IL-1{beta}, IL-6, and CXCL-8 (p<0.001). The pEtN-conjugated LPS triggered a significantly greater production of TNF-, IL-6, and CXCL-8 compared to L-Ara4N (p<0.05). This study reveals that the colistin MIC value can significantly predict lipid A modification in clinical K. pneumoniae, and differences in resistance-mediated lipid A modification result in variation in the immunological response. This study highlights the potential of dynamic host-pathogen interaction in the context of colistin resistance.

microbiology↗

bioRxiv2024

A novel isoform of Tensin1 promotes actin filament assembly for efficient erythroblast enucleation

Mammalian red blood cells are generated via a terminal erythroid differentiation pathway culminating in cell polarization and enucleation. Actin filament polymerization is critical for enucleation, but the molecular regulatory mechanisms remain poorly understood. We utilized publicly available RNA-seq and proteomics datasets to mine for actin-binding proteins and actin- nucleation factors differentially expressed during human erythroid differentiation and discovered that a focal adhesion protein--Tensin-1--dramatically increases in expression late in differentiation. Remarkably, we found that differentiating human CD34+ cells express a novel truncated form of Tensin-1 (eTNS1; Mr [~]125 kDa) missing the N-terminal half of the protein, due to an internal mRNA translation start site resulting in a unique exon 1. eTNS1 localized to the cytoplasm during terminal erythroid differentiation, with no apparent membrane association or focal adhesion formation. Knocking out eTNS1 had no effect on assembly of the spectrin membrane skeleton but led to impaired enucleation and absent or mis-localized actin filament foci in enucleating erythroblasts. We conclude that eTNS1 is a novel regulator of actin filament assembly during human erythroid terminal differentiation required for efficient enucleation.

cell biology↗

bioRxiv2024

A Ketogenic Diet Sensitizes Pancreatic Cancer to Inhibition of Glutamine Metabolism

Pancreatic cancer is the third leading cause of cancer death in the United States, and while conventional chemotherapy remains the standard treatment, responses are poor. Safe and alternative therapeutic strategies are urgently needed1. A ketogenic diet has been shown to have anti-tumor effects across diverse cancer types but will unlikely have a significant effect alone. However, the diet shifts metabolism in tumors to create new vulnerabilities that can be targeted (1). Modulators of glutamine metabolism have shown promise in pre-clinical models but have failed to have a marked impact against cancer in the clinic. We show that a ketogenic diet increases TCA and glutamine-associated metabolites in murine pancreatic cancer models and under metabolic conditions that simulate a ketogenic diet in vitro. The metabolic shift leads to increased reliance on glutamine-mediated anaplerosis to compensate for low glucose abundance associated with a ketogenic diet. As a result, glutamine metabolism inhibitors, such as DON and CB839 in combination with a ketogenic diet had robust anti-cancer effects. These findings provide rationale to study the use of a ketogenic diet with glutamine targeted therapies in a clinical context. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/604377v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1ebeefforg.highwire.dtl.DTLVardef@97e2ceorg.highwire.dtl.DTLVardef@1ab45c3org.highwire.dtl.DTLVardef@1713540_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical Abstract Description: Mechanistic rationale for combining a ketogenic diet and glutamine metabolism inhibitors. The combination of low glucose from a ketogenic diet and pharmacologic glutamine inhibition impairs nutrient input to mitochondria, reducing cancer growth.

cancer biology↗

bioRxiv2018

Dynamic functional connectivity changes in dementia with Lewy bodies and Alzheimer’s disease

We studied the dynamic functional connectivity profile of dementia with Lewy bodies (DLB) and Alzheimers disease (AD) and the relationship between dynamic connectivity and the temporally transient symptoms of cognitive fluctuations and visual hallucinations in DLB.\n\nResting state fMRI data from 31 DLB, 29 AD, and 31 healthy control participants were analysed using dual regression to determine between-network functional connectivity. We used a sliding window approach followed by k-means clustering and dynamic network analyses to study dynamic functional connectivity changes associated with AD and DLB. Network measures that showed significant group differences were tested for correlations with clinical symptom severity.\n\nAD and DLB patients spent more time than controls in sparse connectivity configurations with absence of strong positive and negative connections and a relative isolation of motor networks from other networks. Additionally, DLB patients spent less time in a more strongly connected state and the variability of global brain network efficiency was reduced in DLB compared to controls. However, there were no significant correlations between dynamic connectivity measures and clinical scores.\n\nThe loss of global efficiency variability in DLB might indicate the presence of an abnormally rigid brain network and the lack of economical dynamics, factors which could contribute to an inability to respond appropriately to situational demands. However, the absence of significant clinical correlations indicates that the severity of transient cognitive symptoms such as cognitive fluctuations and visual hallucinations might not be directly related to these dynamic connectivity changes observed during a short resting state scan.

neuroscience↗