Biology subjects

Gelhaus, S. L.

Publications and source records attributed to Gelhaus, S. L..

10 recordsLinked to original sources

bioRxiv2025

Proteomic Analysis in Alzheimer's Disease with Psychosis Reveals Separate Molecular Signatures for Core AD Proteinopathy and Postsynaptic Density Disruption

Background and Hypothesis: Alzheimers disease with psychosis (AD+P) is a subgroup of AD patients with more rapid cognitive deterioration. While our previous study showed that AD+P is associated with loss of prefrontal cortex postsynaptic density (PSD) proteins, identifying proteins in the broader cellular environment that influence PSD loss addresses a critical knowledge gap about synaptic dysfunction mechanisms in early disease stages. Study Design: We conducted a proteomic analysis comparing prefrontal grey matter cortex tissue homogenates from elderly normal controls (n=18), individuals with AD+P (n=61), and individuals with AD-P (n=48), all with Braak stages 3-5. Study Results: AD+P showed the most pronounced alterations relative to controls (178 proteins with q<0.05), although alterations in AD-P and AD+P relative to controls were highly similar (R{superscript 2}=0.965, p<0.001). Weighted-gene correlation network analysis (WGCNA) identified four modules significantly associated with disease status comparing AD subjects to controls, but none differed significantly between AD+P and AD-P. We identified 15 proteins significantly correlated with PSD yield across all samples, including ENPP6, linked to AD+P by GWAS. Additionally, PSD yield-associated proteins showed minimal overlap with altered AD proteins (1 of 137). WGCNA revealed one module significantly correlated with PSD yield across all samples, enriched for inflammatory terms. Conclusions: Our findings suggest a model in which AD+P arises from the combination of quantitative alterations within a shared AD proteome profile and a superimposed set of protein alterations correlated with PSD yield that are largely independent of the shared AD proteome, conferring distinct mechanisms of synaptic vulnerability and psychosis risk.

neuroscience↗

bioRxiv2025

Intracellular glutamine fluctuates with nitrogen availability and regulates Mycobacterium smegmatis biofilm formation

Biofilm formation allows pathogenic nontuberculous mycobacteria (NTM) to adhere to household plumbing systems and has been observed in vivo during human infection. Glucose drives NTM aggregation in vitro, and ammonium inhibits it, but the regulatory systems controlling this early step in biofilm formation are not understood. Here, we show that a variety of carbon and nitrogen sources have similar impacts on aggregation in the model NTM Mycobacterium smegmatis as glucose and ammonium, suggesting that the response to these nutrients is general and likely sensed through downstream, integrated signals. Next, we performed a transposon screen in M. smegmatis to uncover these putative regulatory nodes. Our screen revealed that mutating specific genes in the purine and pyrimidine biosynthesis pathways caused an aggregation defect, but supplementing with adenosine and guanosine had no impact on aggregation either in a purF mutant or WT. Realizing that the only genes we hit in purine or pyrimidine biosynthesis were those that utilized glutamine as a nitrogen donor, we pivoted to the hypothesis that intracellular glutamine could be a nitrogen-responsive node affecting aggregation. We tested this hypothesis in defined M63 medium using targeted mass spectrometry. Indeed, intracellular glutamine increased with nitrogen availability and correlated with planktonic growth. Furthermore, a garA mutant, which has an artificially expanded glutamine pool in growth phase, grew solely as planktonic cells even without nitrogen supplementation. Altogether these results establish that intracellular glutamine controls M. smegmatis aggregation, and they introduce flux-dependent sensors as key components of the NTM biofilm regulatory system. ImportanceA subset of nontuberculous mycobacteria (NTM), including Mycobacterium abscessus, are opportunistic pathogens that can cause severe pulmonary infections. M. abscessus is present in showerhead biofilms, one of the reservoirs from which it can infect susceptible individuals. Moreover, M. abscessus can exist as biofilms during pulmonary infections, and biofilm formation in vitro renders M. abscessus more tolerant to antibiotics. The ability to inhibit NTM biofilm formation could therefore help us better prevent and treat NTM infections. However, the regulatory systems controlling NTM biofilm formation, which could include targets for anti-biofilm therapeutics, are poorly understood. The significance of this work is that it reveals intracellular glutamine as an important node controlling initiation of biofilm formation in the model NTM Mycobacterium smegmatis. Building on this foundation, future studies will investigate how NTM biofilms can be dispersed by altering glutamine levels and will describe how NTM translates intracellular glutamine to alteration of surface adhesins.

microbiology↗

bioRxiv2025

Adropin protects against cardiac metabolic remodeling and dysfunction in HFpEF

Cardiometabolic heart failure with preserved ejection fraction (HFpEF) is a heterogenous metabolic disease, which in the heart presents as left ventricle diastolic dysfunction, ventricular stiffness, and myocardial structural remodeling. Deleterious changes in cardiac metabolism are central to HFpEF pathophysiology, and proposed treatments for the disease have focused on repairing these defects. In this study, we used a preclinical mouse model that recapitulates cardiometabolic HFpEF to elucidate the molecular mechanisms driving cardiac dysfunction, and tested whether recombinant Adropin (a liver- and brain-derived endogenous peptide hormone) could reverse observed defects. We show that long-term treatment with Adropin reversed multiple markers of HFpEF-related cardiac dysfunction (including fibrosis, diastolic dysfunction, and cardiomyocyte hypertrophy). Using untargeted metabolomics, we found that Adropin treatment reduced hexosamine biosynthesis pathway activity, leading to a reduction in the O-GlcNAcylation of the cardiac fatty acid oxidation enzyme long chain acyl-CoA dehydrogenase (LCAD). Reducing LCAD O-GlcNAcylation increased LCAD activity in vitro, and reduced the accumulation of long-chain acylcarnitines in HFpEF mouse hearts in vivo. Our results suggest that Adropin may restore cardiac metabolic function in HFpEF, and that targeting this pathway may be a novel therapeutic avenue for this disease. CLINICAL PERSPECTIVE- Adropin is a circulating liver- and brain-derived peptide that regulates energy metabolism in the heart and other high metabolic-demand tissues. The plasma abundance of Adropin is decreased in diabetic, hypertensive, and aged individuals; all comorbid risk factors for the development of heart failure with preserved ejection (HFpEF). We therefore examined the potential role of Adropin in HFpEF pathophysiology. - Patients with HFpEF display significant reductions in circulating Adropin levels, matching those seen in comorbid diseases. In a mouse model of HFpEF, treatment with recombinant Adropin reduced diastolic dysfunction, cardiac fibrosis, and cardiomyocyte hypertrophy. - These data suggest that targeting the Adropin pathway may represent a new therapeutic approach in HFpEF.

physiology↗

bioRxiv2025

Soma to neuron communication links stress adaptation to stress avoidance behavior

In multicellular organisms, signaling from the nervous system to the peripheral tissues can activate physiological responses to stress. Here, we show that inter-tissue stress communication can also function in reverse, i.e. from the peripheral tissue to the nervous system. osm-8 mutants, which activate the physiological osmotic stress response in the C. elegans skin, also exhibit defective osmotic avoidance (Osm) behavior, via a direct and specific effect on ASH osmosensory neuron excitability. Both osm-8 and the Patched-related gene ptr-23, mutations in which suppress all osm-8 phenotypes, function in the hypodermal lysosomes to regulate both physiology and behavior. Unbiased lipidomics shows that osm-8 leads to a ptr-23-dependent elevation of the lysosome specific lipid bis(monoacylglycero)phosphate (BMP) and expansion of the pool of hypodermal lysosomes. Just as genetic activation of the osmotic stress response by loss of osm-8 in the hypodermis causes an Osm phenotype, acute physiological exposure to osmotic stress also confers a reversible Osm phenotype. Behavioral and genetic plasticity requires biosynthesis of the compatible solute glycerol, a key physiological output of the organismal osmotic stress response. However, ptr-23 is only required for osm-8 induced behavioral plasticity and not physiological plasticity. Instead, both genetic and physiologically induced Osm phenotypes require the unusual non-neuronal lysosomal V-ATPase subunit vha-5, which is also critical for organismal osmotic stress survival. Together, these data reveal that genetic or physiological activation of stress signaling from the skin elicits lysosome-associated signals that modulate organismal neurophysiology to attenuate a sensory neuron circuit. Such body-brain interoceptive communication may allow organisms to better match neuronal decision-making with organismal physiological state.

physiology↗

bioRxiv2025

Cardiac-specific deletion of GCN5L1 promotes fatty liver disease in HFpEF

The prevalence of cardiometabolic heart failure with preserved ejection fraction (HFpEF) continues to grow, representing over half of heart failure cases in the United States. As no specific medication for HFpEF exists, treatment guidelines focus on the management of comorbidities related to metabolic syndrome (e.g. obesity, diabetes, hypertension) that promote the disease1. These same comorbidities also drive pathology in non-cardiac tissues, and the links between cardiometabolic disease presentations in different organs are increasingly being recognized. Preclinical studies on the potential crosstalk between HFpEF and metabolic disease in the liver (e.g. metabolic dysfunction-associated liver disease; MASLD) have focused on how liver dysfunction may affect the heart, particularly through the release of secreted liver proteins. This may reflect the situation in the clinic, where incident MASLD is a risk factor for future HFpEF development. Here, in contrast to this developing paradigm of liver-initiated cardiac disease, we report for the first time a defect in cardiac metabolism related to the mitochondrial metabolic protein GCN5L1 that drives hepatic steatosis and MASLD in HFpEF.

physiology↗

bioRxiv2024

AMPK agonism optimizes the in vivo persistence and anti-leukemia efficacy of chimeric antigen receptor T cells

BACKGROUNDChimeric antigen receptor T cell (CART) therapy has seen great clinical success. However, up to 50% of leukemia patients relapse and long-term survivor data indicate that CART cell persistence is key to enforcing relapse-free survival. Unfortunately, ex vivo expansion protocols often drive metabolic and functional exhaustion, reducing in vivo efficacy. Preclinical models have demonstrated that redirecting metabolism ex vivo can improve in vivo T cell function and we hypothesized that exposure to an agonist targeting the metabolic regulator AMP-activated protein kinase (AMPK), would create CARTs capable of both efficient leukemia clearance and increased in vivo persistence. METHODSCART cells were generated from healthy human via lentiviral transduction. Following activation, cells were exposed to either Compound 991 or DMSO for 96 hours, followed by a 48-hour washout. During and after agonist treatment, T cells were harvested for metabolic and functional assessments. To test in vivo efficacy, immunodeficient mice were injected with luciferase+ NALM6 leukemia cells, followed one week later by either 991- or DMSO-expanded CARTs. Leukemia burden and anti-leukemia efficacy was assessed via radiance imaging and overall survival. RESULTSHuman T cells expanded in Compound 991 activated AMPK without limiting cellular expansion and gained both mitochondrial density and improved handling of reactive oxygen species (ROS). Importantly, receipt of 991-exposed CARTs significantly improved in vivo leukemia clearance, prolonged recipient survival, and increased CD4+ T cell yields at early times post-injection. Ex vivo, 991 agonist treatment mimicked nutrient starvation, increased autophagic flux, and promoted generation of mitochondrially-protective metabolites. DISCUSSIONEx vivo expansion processes are necessary to generate sufficient cell numbers, but often promote sustained activation and differentiation, negatively impacting in vivo persistence and function. Here, we demonstrate that promoting AMPK activity during CART expansion metabolically reprograms cells without limiting T cell yield, enhances in vivo anti-leukemia efficacy, and improves CD4+ in vivo persistence. Importantly, AMPK agonism achieves these results without further modifying the expansion media, changing the CART construct, or genetically altering the cells. Altogether, these data highlight AMPK agonism as a potent and readily translatable approach to improve the metabolic profile and overall efficacy of cancer-targeting T cells.

immunology↗

bioRxiv2024

Myoglobin Inhibits Breast Cancer Cell Fatty Acid Oxidation and Migration via Heme-Dependent Oxidant Production and Not Fatty Acid Binding

The monomeric heme protein myoglobin (Mb), traditionally thought to be expressed exclusively in cardiac and skeletal muscle, is now known to be expressed in approximately 40% of breast tumors. While Mb expression is associated with better patient prognosis, the molecular mechanisms by which Mb limits cancer progression are unclear. In muscle, Mbs predominant function is oxygen storage and delivery, which is dependent on the proteins heme moiety. However, prior studies demonstrate that the low levels of Mb expressed in cancer cells preclude this function. Recent studies propose a novel fatty acid binding function for Mb via a lysine residue (K46) in the heme pocket. Given that cancer cells can upregulate fatty acid oxidation (FAO) to maintain energy production for cytoskeletal remodeling during cell migration, we tested whether Mb-mediated fatty acid binding modulates FAO to decrease breast cancer cell migration. We demonstrate that the stable expression of human Mb in MDA-MB-231 breast cancer cells decreases cell migration and FAO. Site-directed mutagenesis of Mb to disrupt Mb fatty acid binding did not reverse Mb-mediated attenuation of FAO or cell migration in these cells. In contrast, cells expressing Apo-Mb, in which heme incorporation was disrupted, showed a reversal of Mb-mediated attenuation of FAO and cell migration, suggesting that Mb attenuates FAO and migration via a heme-dependent mechanism rather than through fatty acid binding. To this end, we show that Mbs heme-dependent oxidant generation propagates dysregulated gene expression of migratory genes, and this is reversed by catalase treatment. Collectively, these data demonstrate that Mb decreases breast cancer cell migration, and this effect is due to heme-mediated oxidant production rather than fatty acid binding. The implication of these results will be discussed in the context of therapeutic strategies to modulate oxidant production and Mb in tumors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=137 HEIGHT=200 SRC="FIGDIR/small/591659v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@84f5f9org.highwire.dtl.DTLVardef@130b7eeorg.highwire.dtl.DTLVardef@17b96faorg.highwire.dtl.DTLVardef@f517a5_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical Abstract:C_FLOATNO Mb-dependent oxidant generation (but not fatty acid binding) dysregulates mitochondrial respiration and migratory gene expression, leading to decreased cell migration. Created with BioRender. C_FIG HighlightsO_LIMyoglobin (Mb) expression in MDA-MB-231 breast cancer cells slows migration. C_LIO_LIMb expression decreases mitochondrial respiration and fatty acid oxidation. C_LIO_LIMb-dependent fatty acid binding does not regulate cell migration or respiration. C_LIO_LIMb-dependent oxidant generation decreases mitochondrial metabolism and migration. C_LIO_LIMb-derived oxidants dysregulate migratory gene expression. C_LI

cancer biology↗

bioRxiv2024

Lipoxin A4 yields an electrophilic 15-oxo metabolite that mediates FPR2 receptor-independent anti-inflammatory signaling

The enzymatic oxidation of arachidonic acid is proposed to yield trihydroxytetraene species (termed lipoxins) that resolve inflammation via ligand activation of the formyl peptide receptor, FPR2. While cell and murine models activate signaling responses to synthetic lipoxins, primarily 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid (lipoxin A4, LXA4), there are expanding concerns about the biological formation, detection and signaling mechanisms ascribed to LXA4 and related di- and tri-hydroxy {omega}-6 and {omega}-3 fatty acids. Herein, the generation and actions of LXA4 and its primary 15-oxo metabolite were assessed in control, LPS-activated and arachidonic acid supplemented RAW 264.7 macrophages. Despite protein expression of all enzymes required for LXA4 synthesis, both LXA4 and its 15-oxo-LXA4 metabolite were undetectable. Moreover, synthetic LXA4 and the membrane permeable 15-oxo-LXA4 methyl ester that is rapidly de-esterified to 15-oxo-LXA4, displayed no ligand activity for the putative LXA4 receptor FPR2, as opposed to the FPR2 ligand WKYMVm. Alternatively, 15-oxo-LXA4, an electrophilic ,{beta}-unsaturated ketone, alkylates nucleophilic amino acids such as cysteine to modulate redox-sensitive transcriptional regulatory protein and enzyme function. 15-oxo-LXA4 activated nuclear factor (erythroid related factor 2)-like 2 (Nrf2)-regulated gene expression of anti-inflammatory and repair genes and inhibited nuclear factor (NF)-{kappa}B-regulated pro-inflammatory mediator expression. LXA4 did not impact these macrophage anti-inflammatory and repair responses. In summary, these data show an absence of macrophage LXA4 formation and receptor-mediated signaling actions. Rather, if LXA4 were present in sufficient concentrations, this, and other more abundant mono- and poly-hydroxylated unsaturated fatty acids can be readily oxidized to electrophilic ,{beta}-unsaturated ketone products that modulate the redox-sensitive cysteine proteome via G-protein coupled receptor-independent mechanisms.

biochemistry↗

bioRxiv2023

ATR promotes mTORC1 activation via de novo cholesterol synthesis in p16-low cancer cells

DNA damage and cellular metabolism exhibit a complex interplay characterized by bidirectional feedback mechanisms. Key mediators of the DNA damage response and cellular metabolic regulation include Ataxia Telangiectasia and Rad3-related protein (ATR) and the mechanistic Target of Rapamycin Complex 1 (mTORC1), respectively. Previous studies have established ATR as a regulatory upstream factor of mTORC1 during replication stress; however, the precise mechanisms by which mTORC1 is activated in this context remain poorly defined. Additionally, the activity of this signaling axis in unperturbed cells has not been extensively investigated. Here, we demonstrate that ATR promotes mTORC1 activity across various cellular models under basal conditions. This effect is particularly enhanced in cells following the loss of p16, which we have previously associated with hyperactivation of mTORC1 signaling and here found have increased ATR activity. Mechanistically, we found that ATR promotes de novo cholesterol synthesis and mTORC1 activation through the upregulation of lanosterol synthase (LSS), independently of both CHK1 and the TSC complex. Furthermore, the attenuation of mTORC1 activity resulting from ATR inhibition was rescued by supplementation with lanosterol or cholesterol in multiple cellular contexts. This restoration corresponded with enhanced localization of mTOR to the lysosome. Collectively, our findings demonstrate a novel connection linking ATR and mTORC1 signaling through the modulation of cholesterol metabolism.

cancer biology↗

bioRxiv2023

Alternate splice variants of the mitochondrial fission protein DNM1L/Drp1 regulate mitochondrial dynamics and cell fate in ovarian cancer.

Aberrant mitochondrial fission/fusion dynamics have been reported in cancer cells. While post translational modifications are known regulators of the mitochondrial fission/fusion machinery, we show that alternative splice variants of the fission protein Drp1 (DNM1L) have specific and unique roles in cancer, adding to the complexity of mitochondrial fission/fusion regulation in tumor cells. Ovarian cancer specimens express an alternative splice transcript variant of Drp1 lacking exon 16 of the variable domain, and high expression of this splice variant relative to other transcripts is associated with poor patient outcome. Unlike the full-length variant, expression of Drp1 lacking exon 16 leads to decreased association of Drp1 to mitochondrial fission sites, more fused mitochondrial networks, enhanced respiration, and TCA cycle metabolites, and is associated with a more metastatic phenotype in vitro and in vivo. These pro-tumorigenic effects can also be inhibited by specific siRNA-mediated inhibition of the endogenously expressed transcript lacking exon 16. Moreover, lack of exon 16 abrogates mitochondrial fission in response to pro-apoptotic stimuli and leads to decreased sensitivity to chemotherapeutics. These data emphasize the significance of the pathophysiological consequences of Drp1 alternative splicing and divergent functions of Drp1 splice variants, and strongly warrant consideration of Drp1 splicing in future studies.

cancer biology↗