Biology subjects

Park, C.

Publications and source records attributed to Park, C..

At least 73 records · Page 4Linked to original sources

bioRxiv2023

Murine Alveolar Macrophages Rapidly Accumulate Intranasally Administered SARS-CoV-2 Spike Protein leading to Neutrophil Recruitment and Damage

The trimeric SARS-CoV-2 Spike protein mediates viral attachment facilitating cell entry. Most COVID-19 vaccines direct mammalian cells to express the Spike protein or deliver it directly via inoculation to engender a protective immune response. The trafficking and cellular tropism of the Spike protein in vivo and its impact on immune cells remains incompletely elucidated. In this study we inoculated mice intranasally, intravenously, and subcutaneously with fluorescently labeled recombinant SARS-CoV-2 Spike protein. Using flow cytometry and imaging techniques we analyzed its localization, immune cell tropism, and acute functional impact. Intranasal administration led to rapid lung alveolar macrophage uptake, pulmonary vascular leakage, and neutrophil recruitment and damage. When injected near the inguinal lymph node medullary, but not subcapsular macrophages, captured the protein, while scrotal injection recruited and fragmented neutrophils. Wide-spread endothelial and liver Kupffer cell uptake followed intravenous administration. Human peripheral blood cells B cells, neutrophils, monocytes, and myeloid dendritic cells all efficiently bound Spike protein. Exposure to the Spike protein enhanced neutrophil NETosis and augmented human macrophage TNF- and IL-6 production. Human and murine immune cells employed C-type lectin receptors and Siglecs to help capture the Spike protein. This study highlights the potential toxicity of the SARS-CoV-2 Spike protein for mammalian cells and illustrates the central role for alveolar macrophage in pathogenic protein uptake.

immunology↗

bioRxiv2023

Commensal Bacteria Maintain a Qa-1b-restricted Unconventional CD8+ T Population in Gut Epithelium

Intestinal intraepithelial lymphocytes (IELs) are characterized by an unusual phenotype and developmental pathway, yet their specific ligands and functions remain largely unknown. Here by analysis of QFL T cells, a population of CD8+ T cells critical for monitoring the MHC I antigen processing pathway, we established that unconventional Qa-1b-restricted CD8+ T cells are abundant in intestinal epithelium. We found that QFL T cells showed a Qa-1b-dependent unconventional phenotype in the spleen and small intestine of naive wild-type mice. The splenic QFL T cells showed innate-like functionality exemplified by rapid response to cytokines or antigen, while the gut population was refractory to stimuli. Microbiota was required for the maintenance, but not the initial gut homing of QFL T cells. Moreover, monocolonization with Pediococcus pentosaceus, which expresses a peptide that cross-activated QFL T cells, was sufficient to maintain QFL T cells in the intestine. Thus, microbiota is critical for shaping the Qa-1b-restricted IEL landscape.

immunology↗

bioRxiv2022

Rapid iPSC inclusionopathy models shed light on formation, consequence and molecular subtype of alpha-synuclein inclusions

Intracellular inclusions accompanying neurodegeneration are histopathologically and ultrastructurally heterogeneous but the significance of this heterogeneity is unclear. iPSC models, while promising for disease modeling, do not form inclusions in a reasonable timeframe and suffer from limited tractability. Here, we developed an iPSC toolbox utilizing piggyBac-based or targeted transgenes to rapidly induce CNS cells with concomitant expression of aggregation-prone proteins. This system is amenable to screening and longitudinal tracking at single-cell and single-inclusion resolution. For proof-of-principle, cortical neuron -synuclein "inclusionopathy" models were engineered to form inclusions through exogenous seeding or -synuclein mutation. These models recapitulated known fibril- and lipid-rich inclusion subtypes, uncovering dynamic interactions between them, and refined the classification of inclusions in postmortem brain. Genetic-modifier and protein-interaction screens pinpointed proteins like RhoA whose sequestration into specific inclusion subtypes is likely to be toxic. This iPSC platform should enhance our understanding of proteinaceous pathologies in neurodegeneration and facilitate therapeutics development.

neuroscience↗

bioRxiv2022

A personal, reference quality, fully annotated genome from a Saudi individual

We have used multiple sequencing approaches to sequence the genome of a volunteer from Saudi Arabia. We use the resulting data to generate a de novo assembly of the genome, and use different computational approaches to refine the assembly. As a consequence, we provide a contiguous assembly of the complete genome of an individual from Saudi Arabia for all chromosomes except chromosome Y, and label this assembly KSA001. We transferred genome annotations from reference genomes and predicted genome features using methods from Artificial Intelligence to fully annotate KSA001, and we make all primary sequencing data, the assembly, and the genome annotations freely available in public databases using the FAIR data principles.

bioinformatics↗

bioRxiv2022

TRPA1 activation in non-sensory supporting cells contributes to regulation of cochlear sensitivity after acoustic trauma

TRPA1 channels are expressed in nociceptive neurons, where they detect noxious stimuli, and in the mammalian cochlea, where their function is unknown. Here we show that TRPA1 activation in the supporting non-sensory Hensens cells causes prolonged Ca2+ responses, which propagate across the organ of Corti and cause long-lasting contractions of pillar and Deiters cells. Caged Ca2+ experiments demonstrated that, similar to Deiters cells, pillar cells also possess Ca2+-dependent contractile machinery. TRPA1 channels are activated by endogenous products of oxidative stress and by extracellular ATP. Since both these stimuli are present in vivo after acoustic trauma, TRPA1 activation after noise may affect cochlear sensitivity through supporting cell contractions. Consistently, TRPA1 deficiency results in larger but less prolonged noise-induced temporary shift of hearing thresholds, accompanied by permanent changes of latency and shape of the auditory brainstem responses. We conclude that TRPA1 contributes to the regulation of cochlear sensitivity after acoustic trauma.

neuroscience↗

bioRxiv2022

Loss of Linker Histone H1 in the Maternal Genome Influences DEMETER-Mediated Demethylation and Affects the Endosperm DNA Methylation Landscape

The Arabidopsis DEMETER (DME) DNA glycosylase demethylates the central cell genome prior to fertilization. This epigenetic reconfiguration of the female gamete companion cell establishes gene imprinting in the endosperm and is essential for seed viability. DME demethylates small and genic-flanking transposons as well as intergenic and heterochromatin sequences, but how DME is recruited to these target loci remains unknown. H1.2 was identified as a DME-interacting protein in a yeast two-hybrid screen, and maternal genome H1 loss affects DNA methylation and expression of selected imprinted genes in the endosperm. Yet, the extent to which how H1 influences DME demethylation and gene imprinting in the Arabidopsis endosperm has not been investigated. Here, we showed that unlike in the vegetative cell, both canonical histone H1 variants are present in the central cell. Our endosperm methylome analysis revealed that without the maternal linker histones, DME-mediated demethylation is facilitated, particularly in the heterochromatin regions, indicating that H1-containing nucleosomes are barriers for DME demethylation. Loss of H1 in the maternal genome has a very limited effect on gene transcription or gene imprinting regulation in the endosperm; however, it variably influences euchromatin TE methylation and causes a slight hypermethylation and a reduced expression in selected imprinted genes. We conclude that loss of maternal H1 indirectly influences DME-mediated demethylation and endosperm DNA methylation landscape but does not appear to affect endosperm gene transcription and overall imprinting regulation.

plant biology↗

bioRxiv2022

A Long-Circulating Vector for Aptamers Based upon Polyphosphodiester-Backboned Molecular Brushes

Aptamers face challenges for use outside the ideal conditions in which they are developed. These difficulties are most palpable in vivo due to nuclease activities, rapid clearance, and off-target binding. Herein, we demonstrate that a polyphosphodiester-backboned molecular brush can suppress enzymatic digestion, reduce non-specific cell uptake, enable long blood circulation, and rescue the bioactivity of a conjugated aptamer in vivo. The backbone along with the aptamer is assembled via solid-phase synthesis, followed by installation of poly(ethylene glycol) (PEG) side chains using a two-step process with near-quantitative efficiency. The synthesis allows for precise control over polymer size and architecture. Consisting entirely of building blocks that are generally recognized as safe for therapeutics, this novel molecular brush is expected to provide a highly translatable route for aptamer-based therapeutics.

pharmacology and toxicology↗

bioRxiv2022

Adaptive duplication and functional diversification of Protein kinase R contribute to the uniqueness of bat-virus interactions

Several bat species act as asymptomatic reservoirs for many viruses that are instead highly pathogenic in other mammals. Here, we have characterized the functional diversification of the Protein kinase R (PKR), a major antiviral innate defense system. Our data indicate that PKR has evolved under positive selection and has undergone repeated genomic duplications in bats, in contrast to all studied mammals that possess a single copy of the gene. Functional testing of the relationship between PKR and poxvirus antagonists revealed how an evolutionary conflict with ancient pathogenic poxviruses has shaped a specific bat host-virus interface. More importantly, we determined that duplicated PKRs of the Myotis species have undergone functional diversification allowing them to collectively escape from and enhance control of DNA and RNA viruses. These findings suggest that viral-driven adaptations in PKR contribute to modern virus-bat interactions and may account for bat specific immunity.

evolutionary biology↗

bioRxiv2022

Peroxiredoxin 5 regulates osteogenic differentiation via interaction with hnRNPK during bone regeneration

Peroxiredoxin 5 (Prdx5) is involved in pathophysiological regulation via the stress-induced cellular response. However, the function of Prdx5 in the bone remains largely unknown. Here, we show that Prdx5 is involved in osteoclast and osteoblast differentiation, resulting in osteoporotic phenotypes in Prdx5 knockout (Prdx5Ko) mice. Through immunoprecipitation and liquid chromatography combined with tandem mass spectrometry analysis, heterogeneous nuclear ribonucleoprotein K (hnRNPK) was identified as a potential binding partner of Prdx5 during osteoblast differentiation in vitro. We found that Prdx5 acts as a negative regulator of hnRNPK-mediated osteocalcin (Ocn) expression. In addition, transcriptomic analysis revealed that in vitro differentiated osteoclasts from the bone marrow-derived macrophages of Prdx5Ko mice showed enhanced expression of several osteoclast-related genes. These findings indicate that Prdx5 might contribute to the maintenance of bone homeostasis by regulating osteoblast differentiation. This study proposes a new function of Prdx5 in bone remodeling that may be used in developing therapeutic strategies for bone diseases.

cell biology↗

bioRxiv2022

G protein-coupled receptor 151 regulates glucose metabolism and hepatic gluconeogenesis

Human genetics has been instrumental in identification of genetic variants linked to type 2 diabetes (T2D). Recently a rare, putative loss-of-function mutation in the orphan G-protein coupled receptor 151 (GPR151) was found to be associated with lower odds ratio for T2D, but the mechanism behind this association has remained elusive. Here for the first time we show that Gpr151 is a fasting- and glucagon-responsive hepatic gene which regulates hepatic gluconeogenesis. Gpr151 ablation in mice leads to suppression of hepatic gluconeogenesis genes and reduced hepatic glucose production in response to pyruvate. Importantly, the restoration of hepatic Gpr151 levels in the Gpr151 knockout mice reverses the reduced hepatic glucose production. Our findings establish a previously unknown role of Gpr151 in the liver and provides an explanation to the lowered T2D risk in individuals with nonsynonymous mutations in GPR151. This study highlights the therapeutic potential of targeting GPR151 for treatment of metabolic disease.

physiology↗

bioRxiv2022

Programmable RNA Sensing for Cell Monitoring and Manipulation

RNAs are the central and universal mediator of genetic information underlying the diversity of cell types and cell states, which together shape tissue organization and organismal function across species and life spans. Despite advances in RNA sequencing and massive accumulation of transcriptome datasets across life sciences, the dearth of technologies that leverage RNAs to observe and manipulate cell types remains a prohibitive bottleneck in biology and medicine. Here, we describe CellREADR (Cell access through RNA sensing by Endogenous ADAR), a programmable RNA sensing technology that leverages RNA editing mediated by ADAR (adenosine deaminase acting on RNA) for coupling the detection of cell-defining RNAs with translation of effector proteins. Viral delivery of CellREADR conferred specific cell type access in mouse and rat brains and in ex vivo human brain tissues. Furthermore, CellREADR enabled recording and control of neuron types in behaving mice. CellREADR thus highlights the potential for RNA-based monitoring and editing of animal cells in ways that are specific, versatile, easy, and generalizable across organ systems and species, with broad applications in biology, biotechnology, and programmable RNA medicine.

molecular biology↗

bioRxiv2022

USP11 promotes endothelial apoptosis-resistance in pulmonary hypertension by deubiquitinating HINT3

IntroductionPulmonary arterial hypertension (PAH) is a progressive, lethal, and incurable disease of the pulmonary vasculature. Evolving evidence indicates that the ubiquitin-specific proteases (USPs), play an important role in the pathogenesis of PAH by deubiquitinating key proteins involved in cell proliferation, migration, and apoptosis. Our genome-wide association study (GWAS) analysis-paired with transcriptomic profiling indicated that deubiquitinase USP11 and histidine triad nucleotide binding protein 3 (HINT3) are positively correlated and that their expression increased in lungs of PAH patients compared to control (fail donor) group, and inversely correlated with survival. However, mechanisms and function of the USP11/HNT3 axis have not been explored in PAH. Therefore, we aimed to investigate that HINT3 stabilized by USP11 activation links to endothelial apoptosis-resistance in PAH. Methods and ResultsExpression of USP11 and HINT3 was increased in the lungs of idiopathic PAH (IPAH) patients and Hypoxia/Sugen-treated mice using qRT-PCR and Western blot analyses. USP11 and HINT3 interacted physically as shown by co-immunoprecipitation (co-IP) assay in human pulmonary artery endothelial cells (HPAECs). HINT3 levels were decreased upon transfection of HA-tagged Ubi plasmid into HPAECs. Pretreatment with the potent proteasome inhibitor MG132 prolonged the half-life of HINT3 protein, indicating that HINT3 is degraded by polyubiquitination. HINT3 was stabilized and destabilized by forced overexpression or siRNA knockdown of USP11 respectively. Similarly, treatment with mitoxantrone, a USP11 antagonist, reduced HPAEC HINT3 expression. HINT3 interacted with the antiapoptotic mediator, BCL2. Overexpression of USP11 increased BCL2 content, congruent to elevated lung tissue levels seen in IPAH patients and Hypoxia/Sugen-treated mice. Conversely, knockdown of HINT3 function led to depletion of BCL2. ConclusionsThe HINT3-USP11 axis contributes to apoptosis-resistance in pulmonary artery endothelial cells, as is potentially a novel and attractive therapeutic target for ubiquitination modulators.

physiology↗

bioRxiv2022

PPARγ/ETV2 Axis Regulates Endothelial-to-Mesenchymal Transition in Pulmonary Hypertension

Endothelial-to-mesenchymal transition (EndoMT) plays an important role in pulmonary hypertension (PH). Also, the molecular mechanisms regulating EndoMT in PH remain to be defined. In this study, we first showed that reduced expression of the transcription factors ETV2 (ETS variant 2) and PPAR{gamma} (Peroxisome Proliferator-Activated Receptor gamma) along with reduced endothelial markers and increased EndoMT markers were consistently observed in lungs and pulmonary artery endothelial cells (PAECs) of idiopathic pulmonary arterial hypertension (IPAH) patients, in hypoxia-exposed mouse lungs, human PAECs, and in induced EndoMT cells. Base on this observation, we aimed to investigate the function of ETV2 and PPAR{gamma} in EndoMT. We have explored the function of ETV2 and PPAR{gamma} and its mechanism in PH using in Etv2+/- mice or PPAR{gamma} KO mice. Etv2+/- mice spontaneously developed PH and right ventricular hypertrophy, associated with increased EndoMT markers and decreased EC markers. PPAR{gamma} transcriptionally activated the ETV2 promoter. Endothelial PPAR{gamma} expression in mice is positively correlated with ETV2 expression, but inversely with EndoMT markers. Overexpression of ETV2 in hypoxia-exposed rat pulmonary artery led to vascular relaxation. We conclude that PPAR{gamma}-ETV2 signaling can function as a novel pathway in PH pathogenesis by attenuating EndoMT.

physiology↗

bioRxiv2022

Describing Chemical Kinetics in the Time Dimension with Mean Reaction Time

The chemical kinetics is such a fundamental topic in chemistry. By analyzing how the experimental conditions and parameters influence the reaction rate, chemists have deciphered the molecular details on how the chemical reactions occur. The quantitative analysis of the reaction rate requires the formulation of the rate equation, which describes the dependence of the reaction rate on the concentrations of the reactants and also the rate constants of the elementary steps. Though the methods to derive the rate equation from the kinetic model have been known for a century, it is still mathematically challenging to derive the rate equation for complex reactions with multiple steps, which requires a solution for simultaneous differential equations. Therefore, chemists frequently resort to the steady-state approximation or the numerical simulation. One way to avoid the mathematical difficulty is to describe the chemical kinetics in the time dimension. Describing the mean reaction time, the average of the time required for the completion of the chemical reaction, using the elementary rate constants of the kinetic model is much simpler mathematically than deriving the rate equation for the kinetic model. Here, we describe the basic rules for the derivation of the formula of the mean reaction time, derive the generalized equation for the mean reaction time, and analyze the components of the formula to determine how the individual steps in the complex reaction contribute to the mean reaction time. Being the ensemble-averaged value, the mean reaction time does not provide the information on the actual distribution of the reaction time of individual chemical entity. However, the formula of the mean reaction time reveals invaluable insights on how the energy levels of the ground state and the transition states affect the kinetics of the complex reaction and offers a way to identify the most time-consuming process of the complex reaction in a straightforward manner. We also apply the mean reaction time to enzyme kinetics and demonstrate that one can derive the expressions of the kinetic parameters (kcat/KM and kcat) in a surprisingly simple way even without resorting to the steady-state application.

biochemistry↗

bioRxiv2022

A novel neuroelectrophysiological age index implicates brain health and sleep disorders

Sleep architecture and microstructures alter with aging and sleep disorder-led accelerated aging. We proposed a sleep electroencephalogram (EEG) based brain age prediction model using convolutional neural networks. We then associated the estimated brain age index (BAI) with brain structural aging features, sleep disorders and various sleep parameters. Our model also showed a higher BAI (predicted brain age minus chronological age) is associated with cortical thinning in various functional areas. We found a higher BAI for sleep disorder groups compared to healthy sleepers, as well as significant differences in the spectral pattern of EEG among different sleep disorders (lower power in slow and{vartheta} waves for sleep apnea vs. higher power in {beta} and{sigma} for insomnia), suggesting sleep disorder-dependent pathomechanisms of aging. Our results demonstrate that the new EEG-BAI can be a biomarker reflecting brain health in normal and various sleep disorder subjects, and may be used to assess treatment efficacy.

neuroscience↗

bioRxiv2021

Visual Interpretation of the Meaning of kcat/KM in Enzyme Kinetics

kcat and kcat/KM are the two fundamental kinetic parameters in enzyme kinetics. kcat is the first-order rate constant that determines the reaction rate when the enzyme is fully occupied at a saturating concentration of the substrate. kcat/KM is the second-order rate constant that determines the reaction rate when the enzyme is mostly free at a very low concentration of the substrate. Both parameters provide critical information on how the enzyme lowers the energy barriers along the reaction pathway for catalysis. However, it is surprising how often kcat/KM is used inappropriately as a composite parameter derived by dividing kcat with KM to assess both catalytic power and affinity to the substrate of the enzyme. The main challenge in explaining the true meaning of kcat/KM is the difficulty to demonstrate how the reaction energetics of enzyme catalysis determines kcat/KM in a simple way. Here, I report a step-by-step demonstration on how to visualize the meaning of kcat/KM on the reaction energy diagram. By using the reciprocal form of the expression of kcat/KM with the elementary rate constants in kinetic models, I show that kcat/KM is a harmonic sum of several kinetic terms that correspond to the heights of the transition states relative to the free enzyme. Then, I demonstrate that the height of the highest transition state has the dominant influence on kcat/KM, i. e. the step with the highest transition state is the limiting step for kcat/KM. The visualization of the meaning of kcat/KM on the reaction energy diagram offers an intuitive way to understand all the known properties of kcat/KM, including the Haldane relationship.

biochemistry↗

bioRxiv2021

Ribonucleotide Reductase Regulatory Subunit M2 as a Driver of Glioblastoma TMZ-Resistance through Modulation of dNTP Production

Glioblastoma (GBM) remains one of the most resistant and fatal forms of cancer. Previous studies have examined primary and recurrent GBM tumors, but it is difficult to study tumor evolution during therapy where resistance develops. To investigate this, we performed an in vivo single-cell RNA sequencing screen in a patient-derived xenograft (PDX) model. Primary GBM was modeled by mice treated with DMSO control, recurrent GBM was modeled by mice treated with temozolomide (TMZ), and during therapy GBM was modeled by mice euthanized after two of five TMZ treatments. Our analysis revealed the cellular population present during therapy to be distinct from primary and recurrent GBM. We found the Ribonucleotide Reductase gene family to exhibit a unique signature in our data due to an observed subunit switch to favor RRM2 during therapy. GBM cells were shown to rely on RRM2 during therapy causing RRM2-knockdown (KD) cells to be TMZ-sensitive. Using targeted metabolomics, we found RRM2-KDs to produce less dGTP and dCTP than control cells in response to TMZ (p<0.0001). Supplementing RRM2-KDs with deoxycytidine and deoxyguanosine rescued TMZ-sensitivity, suggesting an RRM2-driven mechanism of chemoresistance, established by regulating the production of these nucleotides. In vivo, tumor-bearing mice treated with the RRM2-inhibitor, Triapine, in combination with TMZ, survived longer than mice treated with TMZ alone (p<0.01), indicating promising clinical opportunities in targeting RRM2. Our data present a novel understanding of RRM2 activity, and its alteration during therapeutic stress as response to TMZ-induced DNA damage.

cancer biology↗

bioRxiv2021

Polycomb group protein CBX7 represses cardiomyocyte proliferation via modulation of the TARDBP/Rbm38 axis

Cardiomyocyte (CM) proliferation notably decreases during the perinatal period. At present, regulatory mechanisms for this loss of proliferative capacity is poorly understood. CBX7, a polycomb group (PcG) protein, regulates the cell cycle but its role in CM proliferation is unknown. Here, we report that CBX7 inhibits proliferation of perinatal CMs by controlling TARDBP/Rbm38 pathway. Gene expression profiling demonstrated that CBX7 expression in the heart was low during the prenatal period, abruptly increased during the perinatal period, and sustained constantly throughout the adulthood. CBX7, when overexpressed via adenoviral transduction in neonatal CMs, reduced proliferation and promoted multinucleation of the CMs. Mutant mice carrying targeted inhibition of CBX7 in CMs exhibited cardiomegaly with increased proliferation of CMs at postnatal stages. Mechanistically, CBX7 interacted with TAR DNA-binding protein 43 (TARDBP) and positively regulated its downstream target, RNA Binding Motif Protein 38 (RBM38). Rbm38 was upregulated in the postnatal hearts and overexpression of RBM38 reduced proliferation of neonatal CMs. Together, this study provides a novel insight into the role of CBX7 in regulation of CM proliferation during the perinatal period.

developmental biology↗