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Ling, J.

Publications and source records attributed to Ling, J..

At least 37 records · Page 2Linked to original sources

A gentle palette of plasma membrane dyes

Plasma membrane stains are one of the most important organelle markers for unambiguous assignments of individual cells and monitoring membrane morphology and dynamics. The state-of-the-art PM stains are bright, specific, fluorogenic, and compatible with super-resolution imaging. However, when recording membrane dynamics, particularly under light-intensive microscopes, PM is prone to photodynamic damages due to its phospholipid bilayer nature. Here we developed PK Mem dyes tailored for time-lapse fluorescence imaging. By integrating triplet-state quenchers into the MemBright dyes featuring cyanine chromophores and amphiphilic zwitterion anchors, PK Mem dyes exhibited a three-fold reduction in phototoxicity and a more than four-fold improvement in photostability in imaging experiments. These dyes enable 2D and 3D imaging of live or fixed cancer cell lines and a wide range of primary cells, at the same time pair well with various fluorescent markers. PK Mem dyes can be applied to neuronal imaging in brain slices and in vivo two-photon imaging. The gentle nature of PK Mem palette enables ultralong-term recording of cell migration and cardiomyocyte beating. Notably, PK Mem dyes are optically compatible with STED/SIM imaging, which can handily upgrade the routine of time-lapse neuronal imaging, such as growth cone tracking and mitochondrial transportations, into nanoscopic resolutions.

neuroscience↗

Integrating molecular and clinical variables to predict myocardial recovery

Mechanical unloading and circulatory support with left ventricular assist devices (LVADs) mediate significant myocardial improvement in a subset of advanced heart failure (HF) patients. The clinical and biological phenomena associated with cardiac recovery are under intensive investigation. Left ventricular (LV) apical tissue, alongside clinical data, were collected from HF patients at the time of LVAD implantation (n=208). RNA was isolated and mRNA transcripts were identified through RNA sequencing and confirmed with RT-qPCR. To our knowledge this is the first study to combine transcriptomic and clinical data to derive predictors of myocardial recovery. We used a bioinformatic approach to integrate 59 clinical variables and 22,373 mRNA transcripts at the time of LVAD implantation for the prediction of post-LVAD myocardial recovery defined as LV ejection fraction (LVEF) [≥]40% and LV end-diastolic diameter (LVEDD) [≤]5.9cm, as well as functional and structural LV improvement independently by using LVEF and LVEDD as continuous variables, respectively. To substantiate the predicted variables, we used a multi-model approach with logistic and linear regressions. Combining RNA and clinical data resulted in a gradient boosted model with 80 features achieving an AUC of 0.731{+/-}0.15 for predicting myocardial recovery. Variables associated with myocardial recovery from a clinical standpoint included HF duration, pre-LVAD LVEF, LVEDD, and HF pharmacologic therapy, and LRRN4CL (ligand binding and programmed cell death) from a biological standpoint. Our findings could have diagnostic, prognostic, and therapeutic implications for advanced HF patients, and inform the care of the broader HF population. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=170 HEIGHT=200 SRC="FIGDIR/small/589326v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@17f0503org.highwire.dtl.DTLVardef@2231c1org.highwire.dtl.DTLVardef@f0ac56org.highwire.dtl.DTLVardef@c278f3_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

Salmonella Typhimurium infection inhibits macrophage IFNbeta signaling in a TLR4-dependent manner

Type I Interferons (IFNs) generally have a protective role during viral infections, but their function during bacterial infections is dependent on the bacterial species. Legionella pneumophila, Shigella sonnei and Mycobacterium tuberculosis can inhibit type I IFN signaling. Here we examined the role of type I IFN, specifically IFN{beta}, in the context of Salmonella enterica serovar Typhimurium (STm) macrophage infections and the capacity of STm to inhibit type I IFN signaling. We demonstrate that IFN{beta} has no effect on the intracellular growth of STm in infected bone marrow derived macrophages (BMDMs) derived from C57BL/6 mice. STm infection inhibits IFN{beta} signaling but not IFN{gamma} signaling in a murine macrophage cell line. We show that this inhibition is independent of the type III and type VI secretion systems expressed by STm and is also independent of bacterial phagocytosis. The inhibition is Toll-like receptor 4 (TLR4)-dependent as the TLR4 ligand, lipopolysaccharide (LPS), alone is sufficient to inhibit IFN{beta}-mediated signaling and STm-infected, TLR4-deficient BMDMs do not exhibit inhibited IFN{beta} signaling. In summary, we show that macrophages exposed to STm have reduced IFN{beta} signaling via crosstalk with TLR4 signaling, and that IFN{beta} signaling does not affect cell autonomous host defense against STm.

microbiology↗

Serine mistranslation induces the integrated stress response without accumulation of uncharged tRNAs

Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes that support robust and accurate protein synthesis. A rapidly expanding number of studies show that mutations in aaRSs lead to multiple human diseases, including neurological disorders and cancer. Much remains unknown about how aaRS mutations impact human health. In particular, how aminoacylation errors affect stress responses and fitness in eukaryotic cells remains poorly understood. The integrated stress response (ISR) is an adaptive mechanism in response to multiple stresses. However, chronic activation of the ISR contributes to the development of multiple diseases (e.g., neuropathies). Here we show that Ser misincorporation into Ala and Thr codons, resulting from aaRS editing defects or mutations in tRNAs, constitutively active the ISR. Such activation does not appear to depend on the accumulation of uncharged tRNAs, implicating that Ser mistranslation may lead to ribosome stalling and collision.

genetics↗

Gentle rhodamines for live-cell fluorescence microscopy

Rhodamines have been continuously optimized in brightness, biocompatibility, and colors to fulfill the demands of modern bioimaging. However, the problem of phototoxicity caused by the excited fluorophore under long-term illumination has been largely neglected, hampering their use in time-lapse imaging. Here we introduce cyclooctatetraene (COT) conjugated rhodamines that span the visible spectrum and exhibit significantly reduced phototoxicity. We identified a general strategy for the generation of Gentle Rhodamines, which preserved their outstanding spectroscopic properties and cell permeability while showing an efficient reduction of singlet-oxygen formation and diminished cellular photodamage. Paradoxically, their photobleaching kinetics do not go hand in hand with reduced phototoxicity. By combining COT-conjugated spirocyclization motifs with targeting moieties, these gentle rhodamines compose a toolkit for time-lapse imaging of mitochondria, DNA, and actin and synergize with covalent and exchangeable HaloTag labeling of cellular proteins with less photodamage than their commonly used precursors. Taken together, the Gentle Rhodamines generally offer alleviated phototoxicity and allow advanced video recording applications, including voltage imaging.

cell biology↗

Enhancing mitochondrial pyruvate metabolism ameliorates myocardial ischemic reperfusion injury.

The established clinical therapy for the treatment of acute myocardial infarction is primary percutaneous coronary intervention (PPCI) to restore blood flow to the ischemic myocardium. PPCI is effective at reperfusing the ischemic myocardium, however the rapid re-introduction of oxygenated blood also can cause ischemia-reperfusion (I/R) injury. Reperfusion injury is the culprit for up to half of the final myocardial damage, but there are no clinical interventions to reduce I/R injury. We previously demonstrated that inhibiting the lactate exporter, monocarboxylate transporter 4 (MCT4), and re-directing pyruvate towards oxidation can blunt isoproterenol-induced hypertrophy. Based on this finding, we hypothesized that the same pathway might be important during I/R. Here, we establish that the pyruvate-lactate metabolic axis plays a critical role in determining myocardial salvage following injury. Post-I/R injury, the mitochondrial pyruvate carrier (MPC), required for pyruvate oxidation, is upregulated in the surviving myocardium following I/R injury. MPC loss in cardiomyocytes caused more cell death with less myocardial salvage, which was associated with an upregulation of MCT4 in the myocardium at risk of injury. We deployed a pharmacological strategy of MCT4 inhibition with a highly selective compound (VB124) at the time of reperfusion. This strategy normalized reactive oxygen species (ROS), mitochondrial membrane potential ({Delta}{psi}), and Ca2+, increased pyruvate entry to TCA cycle, and improved myocardial salvage and functional outcomes following I/R injury. Altogether, our data suggest that normalizing the pyruvate-lactate metabolic axis via MCT4 inhibition is a promising pharmacological strategy to mitigate I/R injury. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/577463v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1a7a9b8org.highwire.dtl.DTLVardef@779e0aorg.highwire.dtl.DTLVardef@128d1f3org.highwire.dtl.DTLVardef@efc1bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

Deficiency in ribosome biogenesis causes streptomycin resistance and impairs motility in Salmonella

The ribosome is the central hub for protein synthesis and the target of many antibiotics. Whereas the majority of ribosome-targeting antibiotics inhibit protein synthesis and are bacteriostatic, aminoglycosides promote protein mistranslation and are bactericidal. Understanding the resistance mechanisms of bacteria against aminoglycosides is not only vital for improving the efficacy of this critically important group of antibiotics but also crucial for studying the molecular basis of translational fidelity. In this work, we analyzed Salmonella mutants evolved in the presence of the aminoglycoside streptomycin (Str) and identified a novel gene rimP to be involved in Str resistance. RimP is a ribosome assembly factor critical for the maturation of the 30S small subunit that binds Str. Deficiency in RimP increases resistance against Str and facilitates the development of even higher resistance. Deleting rimP decreases mistranslation and cellular uptake of Str, and further impairs flagellar motility. Our work thus highlights a previously unknown mechanism of aminoglycoside resistance via defective ribosome assembly.

microbiology↗

BBQ methods: Streamlined workflows for Bacterial Burden Quantification in infected cells by confocal microscopy

Accurate quantification of bacterial burden within macrophages, termed Bacterial Burden Quantification (BBQ), is crucial for understanding host-pathogen interactions. Various methods have been employed, each with strengths and weaknesses. This article addresses limitations in existing techniques and introduces two novel automated methods for BBQ within macrophages based on confocal microscopy data analysis. The first method refines total fluorescence quantification by incorporating filtering steps to exclude uninfected cells, while the second method calculates total bacterial volume per cell to mitigate potential biases in fluorescence-based readouts. These workflows utilize PyImageJ and Cellpose software, providing reliable, unbiased, and rapid quantification of bacterial load. The proposed workflows were validated using Salmonella enterica serovar Typhimurium and Mycobacterium tuberculosis models, demonstrating their effectiveness in accurately assessing bacterial burden. These automated workflows offer valuable tools for studying bacterial interactions within host cells and provide insights for various research applications.

cell biology↗

Mapping the Genetic Interaction Network of PARP inhibitor Response

Genetic interactions have long informed our understanding of the coordinated proteins and pathways that respond to DNA damage in mammalian cells, but systematic interrogation of the genetic network underlying that system has yet to be achieved. Towards this goal, we measured 147,153 pairwise interactions among genes implicated in PARP inhibitor (PARPi) response. Evaluating genetic interactions at this scale, with and without exposure to PARPi, revealed hierarchical organization of the pathways and complexes that maintain genome stability during normal growth and defined changes that occur upon accumulation of DNA lesions due to cytotoxic doses of PARPi. We uncovered unexpected relationships among DNA repair genes, including context-specific buffering interactions between the minimally characterized AUNIP and BRCA1-A complex genes. Our work thus establishes a foundation for mapping differential genetic interactions in mammalian cells and provides a comprehensive resource for future studies of DNA repair and PARP inhibitors.

genomics↗

A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and asymptomatic bacteria

Urinary tract infection is among the most common infections worldwide, and is typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial pathogens and asymptomatic bacteria (ASB) in a human urothelial microtissue model including full stratification/differentiation and urine tolerance. Several uropathogens and ASB-like E. coli invaded intracellularly, suggesting invasion is a shared survival strategy, instead of a virulence hallmark. The E. coli adhesin FimH was required for intracellular community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives) and hijacking of exfoliating cells, while biofilm-like aggregates formed mainly with Pseudomonas and Proteus. Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not ASB, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the tissue, cell and molecular level. One-Sentence SummaryA human urothelial model revealed shared colonization strategies between uropathogens and asymptomatic bacteria, and pathogen-specific innate immune responses

microbiology↗

Distinct Local and Global Functions of Aβ Low-Threshold Mechanoreceptors in Mechanical Pain Transmission

The roles of A{beta} low-threshold mechanoreceptors (LTMRs) in transmitting mechanical hyperalgesia and in alleviating chronic pain have been of great interest but remain contentious. Here we utilized intersectional genetic tools, optogenetics, and high-speed imaging to specifically examine functions of SplitCre labeled A{beta}-LTMRs in this regard. Genetic ablation of SplitCre-A{beta}-LTMRs increased mechanical pain but not thermosensation in both acute and chronic inflammatory pain conditions, indicating their modality-specific role in gating mechanical pain transmission. Local optogenetic activation of SplitCre-A{beta}-LTMRs triggered nociception after tissue inflammation, whereas their broad activation at the dorsal column still alleviated mechanical hypersensitivity of chronic inflammation. Taking all data into consideration, we propose a new model, in which A{beta}-LTMRs play distinctive local and global roles in transmitting and alleviating mechanical hyperalgesia of chronic pain, respectively. Our model suggests a new strategy of global activation plus local inhibition of A{beta}-LTMRs for treating mechanical hyperalgesia.

neuroscience↗

MYPT1 is a non-canonical AKAP that tethers PKA to the MLCP signaling node

The activity of myosin light chain phosphatase (MLCP) is fine-tuned by the phosphorylation status of the MLCP target subunit 1 (MYPT1), which is determined by the antagonistic effects of Rho kinase (ROCK) and cAMP/cGMP-dependent protein kinases (PKA and PKG). PKA is composed of two regulatory (PKA-R, of which four variants exist) and two catalytic (PKAcat) subunits. PKA is targeted to the vicinity of its substrates by binding to A kinase anchoring proteins (AKAPs). MYPT1 is part of a complex signaling node that includes kinases and other enzymes involved in signal transduction. We hypothesized that MYPT1 might function as an AKAP to target PKA to the MLCP signaling node. Using a combination of immunoprecipitation, affinity pulldown and in situ proximity ligation assay (PLA) in human platelets and endothelial cells, we show that MYPT1 directly interacts with all four PKA-R variants and mapped the interaction to a 200 residues long central region of MYPT1. The interaction does not involve the docking and dimerization domain of PKA-R typically required for binding to AKAPs. Using peptide array overlay we identified K595, E676 and the PKA/ROCK kinase substrate motif R693/R694/S695/T696 as critical for the interaction. Substitution of S695, T696 or both by aspartic acid or the corresponding phosphorylated residue abolished binding. Our findings reveal that MYPT1 functions as a non-canonical AKAP to anchor PKA to the vicinity of non-phosphorylated S695/T696, where PKA-R would prevent PKAcat, and potentially also ROCK, from interacting with and phosphorylating MYPT1.

cell biology↗

Behavioral measurements of motor readiness in mice.

Motor planning facilitates rapid and precise execution of volitional movements. Although motor planning has been classically studied in humans and monkeys, the mouse has become an increasingly popular model system to study neural mechanisms of motor planning. It remains yet untested whether mice and primates share common behavioral features of motor planning. We combined videography and a delayed response task paradigm in an autonomous behavioral system to measure motor planning in non-body- restrained mice. Motor planning resulted in both reaction time savings and increased movement accuracy, replicating classic effects in primates. We found that motor planning was reflected in task-relevant body features. Both the specific actions prepared and the degree of motor readiness could be read out online during motor planning. The online readout further revealed behavioral evidence of simultaneous preparation for multiple actions under uncertain conditions. These results validate the mouse as a model to study motor planning, demonstrate body feature movements as a powerful real-time readout of motor readiness, and offer behavioral evidence that motor planning can be a parallel process that permits rapid selection of multiple prepared actions.

neuroscience↗

Genome-wide screening reveals metabolic regulation of translational fidelity

Translational quality control is critical for maintaining the accuracy of protein synthesis in all domains of life. Mutations in aminoacyl-tRNA synthetases and the ribosome are known to affect translational fidelity and alter fitness, viability, stress responses, neuron function, and life span. In this study, we used a high-throughput fluorescence-based assay to screen a knock-out library of Escherichia coli and identified 30 nonessential genes that are critical for maintaining the fidelity of stop-codon readthrough. Most of these identified genes have not been shown to affect translational fidelity previously. Intriguingly, we show that several genes controlling metabolism, including cyaA and guaA, unexpectedly enhance stop-codon readthrough. CyaA and GuaA catalyze the synthesis of cyclic adenosine monophosphate (cAMP) and guanosine monophosphate (GMP), respectively. Both CyaA and GuaA increase the expression of ribosomes and tRNAs, allowing aminoacyl-tRNAs to compete with release factors and suppress stop codons. In addition, the effect of guaA deletion on stop-codon readthrough is abolished by deleting prfC, which encodes release factor 3 (RF3). Our results suggest that nucleotide and carbon metabolism is tightly coupled with translational fidelity.

genetics↗

Higher habitual FODMAP intake is associated with lower body mass index, lower insulin resistance and higher short-chain fatty acid-producing microbiota in people with prediabetes

Aims/hypothesisThe quantity and quality of FODMAPs can alter the relative abundance of gut microbiota with metabolic consequences although similar data are lacking in people with prediabetes. We investigated associations between habitual FODMAP contents, gut microbiota and glucose/insulin responses in subjects with prediabetes. MethodsIn this prospective cross-sectional study, ninety-eight subjects with impaired glucose tolerance (IGT) (mean age: 57{+/-}7 years, 43 % men) had assessment of body composition, 6-point oral glucose tolerance tests (OGTT), Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and 3-day dietary intake. We analysed faecal samples in a sub-group of 20 subjects with IGT and 10 subjects with normal glucose tolerance by 16S rRNA microbiome analysis. ResultsObese subjects with IGT had the lowest daily FODMAP intake compared with their non-overweight and non-obese counterparts (5.7 (3.9-7.9) vs 7.1 (5.0-11.3) vs 9.9 (4.1-22.4) g/day, p=0.024) despite having similar total daily energy intake. Total content of FODMAPs was negatively correlated with body fat. After adjustment for age and gender, total FODMAPs were negatively associated with BMI and HOMA-IR. This remained significant after adjustment for macronutrients and physical activity (p=0.032 and p=0.036 respectively). FODMAP contents were strongly associated with short-chain fatty acid (SCFA)-producing bacteria, such as Lactobacillus (p=0.011), Akkermansia muciniphila (p=0.012), and Bifidobacterium longum (p=0.010), the abundance of which were negatively correlated with 2-hr plasma glucose (r = -0.524, p =0.003). ConclusionIn individuals with IGT, higher habitual FODMAP intake was associated with lower body fat and insulin resistance and increased abundance of SCFA-producing bacteria, calling for interventional studies to evaluate the effects of FODMAP intake in prediabetes.

microbiology↗

Cancer-associated SMARCAL1 loss-of-function mutations promote alternative lengthening of telomeres and tumorigenesis in telomerase-negative glioblastoma cells

Telomere maintenance mechanisms are a hallmark of cancer and are required to enable the replicative immortality of malignant cells. While most cancers activate the enzyme telomerase for telomere maintenance, a subset of cancers (~10-15%) use telomerase-independent mechanisms termed alternative lengthening of telomeres (ALT). ALT is characterized by elevated replication stress at telomeres, telomere synthesis via homology directed-repair mechanisms, and is frequently associated with mutations in the ATRX gene. Because ALT is absent in non-malignant proliferating cells, therapeutic strategies targeting ALT-mediated telomere synthesis is an area of significant translational and clinical interest. We previously showed that a subset of adult GBM patients with ATRX-expressing ALT-positive tumors harbored loss-of-function mutations in the SMARCAL1 gene. SMARCAL1 is an annealing helicase involved in replication fork remodeling and the resolution of replication stress. In this study, we used a patient-derived ALT-positive GBM cell line with native SMARCAL1 deficiency to investigate the role of SMARCAL1 in ALT-mediated telomere synthesis and gliomagenesis in vivo. Our results show that inducible rescue of SMARCAL1 expression suppresses ALT indicators and inhibits de novo telomere synthesis in GBM and osteosarcoma cells, suggesting that SMARCAL1 deficiency plays a functional role in ALT induction in cancers that natively lack SMARCAL1 function. Further, SMARCAL1-deficient ALT-positive cells can be serially propagated in vivo in the absence of detectable telomerase activity, suggesting that the SMARCAL1-deficient ALT phenotype maintains telomeres in a manner that promotes tumorigenesis. In summary, we show that SMARCAL1 loss-of-function mutations are permissive to ALT and promote gliomagenesis. We also established isogenic model systems that permit the dynamic modulation of ALT activity, which will be valuable for future studies aimed at understanding the molecular mechanisms of ALT and for identifying novel anti-cancer therapeutics that target the ALT phenotype.

cancer biology↗

Structures of chloramphenicol acetyltransferase III and E. coli β-ketoacylsynthase III co-crystallized with partially hydrolysed acetyl-oxa(dethia)CoA

Acetyl-CoA is a reactive metabolite that non-productively hydrolyzes in a number of enzyme active sites on the crystallization time frame. In order to elucidate enzyme:acetyl-CoA interactions leading to catalysis, acetyl-CoA substrate analogs are needed. One possible analog for use in structural studies is acetyl-oxa(dethia)CoA (AcOCoA), where the thioester sulfur of CoA is replaced by an oxygen. Here we present structures of chloramphenicol acetyltransferase III (CATIII) and E. coli ketoacylsynthase III (FabH) from crystals grown in the presence of partially hydrolyzed AcOCoA and the respective nucleophile. Based on the structures, the behaviour of AcOCoA differs between the enzymes, with FabH reacting with AcOCoA and CATIII being unreactive. The structure of CATIII reveals insight into the catalytic mechanism, with one active site of the trimer having relatively clear electron density for AcOCoA and chloramphenicol, and the other active sites having weaker density for AcOCoA. One FabH structure has a hydrolyzed AcOCoA product oxa(dethia)CoA (OCoA) and the other FabH structure has an acyl-enzyme intermediate with OCoA. Together these structures provide preliminary insight into the use of AcOCoA for enzyme structure-function studies with different nucleophiles. SynopsisStable analogs of acetyl-CoA are needed to support structure-function studies of acetyltransferase enzymes. We report structures of two enzymes in the presence of an acetyl-CoA analog where the thioester is replaced by an ester.

biochemistry↗

Single cell transcriptomics of human skin equivalent organoids

Several methods for generating human skin equivalent (HSE) organoid cultures are regularly used to study skin biology and test pharmaceuticals, however few studies have thoroughly characterized these systems. To fill this gap, we used single cell-RNA sequencing to compare the cellular states of in vitro HSEs generated from distinct culture methods, HSEs xenografted onto mice, and in vivo epidermis. By combining differential gene expression, pseudotime analyses, splicing kinetics, and spatial localization, we reconstructed HSE keratinocyte differentiation trajectories that recapitulated known in vivo epidermal differentiation pathways and show that HSEs contain many of the major in vivo cellular states. However, HSEs also develop several unique keratinocyte states, an expanded basal stem cell program, and disrupted terminal differentiation. In addition, cell-cell communication modeling showed the presence of EMT-associated signaling pathways not normally active in homeostatic skin and we show that EGF supplementation influences the EMT signature. Lastly, xenografted HSEs at early timepoints post-transplantation significantly rescued many of the observed in vitro deficits, while undergoing a hypoxic response that drove an alternative differentiation lineage. This study highlights the strengths and limitations of organoid cultures and identifies areas for potential innovation.

systems biology↗