Biology subjects

Park, M. A.

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

7 recordsLinked to original sources

bioRxiv2024

Genomic Reconstruction and Dietary Response Assessment of Three Acutalibacteraceae Bacteria Isolated from Fecal Samples of Singapore Subjects.

1.Clostridium leptum, a key player in gut butyrate production, has a profound impact on various facets of intestinal health. A recent clinical trial highlighted a significant increase in the relative abundance of this species in response to dietary interventions using beneficial oils. We isolated microbial strains corresponding to "Clostridium leptum" (at the 16S rRNA gene similarity level) and sequenced their genomes. All three genomes were successfully reconstructed, maintaining the chromosome as a single contig. Subsequent genome-wide analysis unveiled the phylogenetic diversity of the isolates, including the discovery of a new species - Gallacutalibacter singaporense. Based on the reconstructed metabolic model, we predicted the growth condition patterns of this new species and confirmed the predictions in vitro. Leveraging the assembled genomes, we dissected the components of the strong dietary intervention response signal previously ascribed to "C. leptum" and revealed distinct individual dynamics of all three bacteria in the clinical trial context. The transitional behavior of the novel species, in particular, revealed intriguing patterns, blazing the path to uncovering previously unrecognized interactions along the diet - gut microbiome - human health axis.

microbiology↗

bioRxiv2022

The translational role of SOS1 in colorectal cancer

BackgroundIt has been challenging to develop agents directly targeting KRAS driver mutations in colorectal cancer (CRC). Recent efforts have focused on developing inhibitors targeting SOS1 as an attractive approach for KRAS-mutant cancers. Here, we aimed to study the translational role of SOS1 in CRC using patient-derived organoids (PDOs). MethodIn this study, we used CRC PDOs as preclinical models to evaluate their sensitivity to SOS1 inhibitor BI3406 and its cellular effects. We utilized large CRC datasets including GENIE cohort, TCGA PanCancer Atlas, and CPTAC-2 cohort to study the significance of molecular alterations of SOS1 in CRC. To identify potential predictive markers, we performed immunohistochemistry (IHC) on CRC tissue for SOS1/2 protein expression and RNA sequencing to identify discriminative gene sets for sensitivity to SOS1 inhibition. The findings were validated by DepMap data for SOS1 dependency. ResultCRC PDOs instead of cell lines had differential sensitivities to BI3406. There was a significant correlation between SOS1 and SOS2 mRNA expressions (Spearmans {rho} 0.56, p<0.001). SOS1/2 protein expression by IHC were universal with heterogeneous patterns in cancer cells but only minimal to none in surrounding non-malignant cells. SOS1 protein expression was associated with worse overall survival in patients with RAS/RAF mutant CRC (p=0.04). We also found that SOS1/SOS2 protein expression ratio > 1 by IHC (p=0.03) instead of KRAS mutation (p=1) was a better predictive marker to BI3406 sensitivity of CRC PDOs. This was concordant with the significant correlation between SOS1/SOS2 protein expression ratio by mass spectrometry and SOS1 dependency score. RNA-seq and gene set enrichment analysis revealed differentially expressed genes and 7 enriched gene sets involving cholesterol homeostasis, epithelial mesenchymal transition, and TNF/NF{kappa}B signaling in BI3406-resistant CRC PDOs. We further discovered that GTP-bound RAS level underwent rebound at 48 hours upon treatment with BI3406 even in BI3406-sensitive PDOs with no change of KRAS effector genes downstream. Cellular adaptation mechanisms to SOS1 inhibition may involve upregulation of SOS1/2 mRNA and SOS1 protein expressions, which may be overcome by SOS1 knockdown/degradation or synergistic effect of BI3406 with trametinib. ConclusionIn summary, CRC PDOs could serve as better models for translational study of SOS1 in CRC. High SOS1 protein expression was a worse prognostic factor in CRC. High SOS1/SOS2 protein expression ratio predicted sensitivity to SOS1 inhibition and dependency. Our preclinical findings supported further clinical development of SOS1-targeting agents in CRC.

cancer biology↗

bioRxiv2021

CCAR-1 has a novel role in regulating the Caenorhabditis elegans germline

1.The Cell Division Cycle and Apoptosis Regulator (CCAR) protein family members are putative transcription regulators that have been characterized for modulating the cell cycle, apoptosis, metabolism, and the heat shock response. Mammals have two CCAR family members, CCAR1 and CCAR2/DBC1, that evolved from the founding family member CCAR-1 that is expressed in Caenorhabditis elegans. Mammalian CCAR2, the most well-studied family member, has been shown to regulate genes involved in metabolism in cultured cells. However, the regulation of gene expression by CCAR family members at an organismal level is unknown. Here, we use whole transcriptome RNA sequencing to examine the effects of CCAR-1 on gene expression in Caenorhabditis elegans. We show that CCAR-1 regulates germline transcription, reproduction, lifespan, and DNA-damage induced apoptosis. This study shows the role of CCAR-1 in vital physiological functions in the C. elegans germline that have not been investigated before.

genomics↗

bioRxiv2021

Generation of SIV resistant T cells and Macrophages from Nonhuman Primate Induced Pluripotent Stem Cells with Edited CCR5 locus

Adoptive therapies with genetically modified somatic T cells rendered HIV resistant have shown promise for AIDS therapy. A renewable source of HIV resistant human T cells from induced pluripotent stem cells (iPSCs) would further facilitate and broaden the applicability of these therapies. Here, we report successful targeting of the CCR5 locus in iPSCs generated from peripheral blood T cells (T-iPSCs) or fibroblasts (fib-iPSCs) from Mauritian Cynomolgus macaques (MCM), using CRISPR/Cas9 technology. We found that CCR5 editing does not affect pluripotency or hematopoietic and T cell differentiation potentials of fib-iPSCs. However, deletion of CCR5 in T-iPSCs leads to selective loss of their T cell redifferentiation potential without affecting myeloid development. T cells and macrophages produced from CCR5-edited MCM- iPSCs did not support replication of the CCR5-tropic simian immunodeficiency viruses SIVmac239 (T-cell tropic) and SIVmac316 (macrophage-tropic). Overall, these studies provide a platform for further exploration of AIDS therapies based on gene-edited iPSCs in a nonhuman primate preclinical model.

cell biology↗

bioRxiv2020

The role of cytosolic polyadenylation element binding protein 2 alternative splicing in hypoxia

HIF1 (Hypoxia-inducible Factor 1) is a transcription factor that plays a crucial role in the hypoxia stress response. However, chronic hypoxia exposure can cause irreversible physiological changes that can lead to pulmonary hypertension (PH), and the need for therapeutics to ameliorate these conditions is great and unmet. Previous studies in our lab have demonstrated that CPEB2 (cytoplasmic polyadenylation element binding protein 2) is a translational repressor of one of the HIF1 subunits: HIF1. Our lab demonstrated that the alternatively spliced CPEB2A isoform of CPEB2 is a repressor of translation, while the CPEB2B isoform is a translational activator of HIF1 during hypoxia, suggesting a major regulatory role for CPEB2 AS in the pulmonary hypoxic response. Although it is well established that during hypoxia, HIF1 levels are dramatically upregulated due to a decrease in the degradation of this factor, we propose that during chronic hypoxia, the expression of HIF1 is maintained via a translational mechanism, likely alongside a decrease in proteolytic degradation. In this study we demonstrate that depletion of the CPEB2B splice isoform has an inhibitory effect on the translation of nascent HIF1 protein during chronic hypoxia, but not the acute phase. We further demonstrate this pathway is dependent on the initiation factor eIF3H. Finally, we show data that indicate CPEB2A and CPEB2B bind differentially to cytoplasmic polyadenylation element consensus sequences depending on the surrounding sequence context. These findings are important since they provide evidence for the potential of CPEB2 to act as a therapeutic target for treating chronic hypoxia-related pulmonary diseases.

cell biology↗

bioRxiv2018

Solution and gas-phase modifiers effect on heme proteins environment and conformational space

The molecular environment is known to impact the secondary and tertiary structure of biomolecules, shifting the equilibrium between different conformational and oligomerization states. In the present study, the effect of solution additives and gas-phase modifiers on the molecular environment of two common heme proteins, bovine cytochrome c and equine myoglobin, is investigated as a function of the time after desolvation (e.g., 100 - 500 ms) using trapped ion mobility spectrometry - mass spectrometry. Changes in the mobility profiles are observed depending on the starting solution composition (i.e., in aqueous solution at neutral pH or in the presence of organic content: methanol, acetone, or acetonitrile) depending on the protein. In the presence of gas-phase modifiers (i.e., N2 containing methanol, acetone, or acetonitrile), a shift in the mobility profiles driven by the gas-modifier mass and size and changes in the relative abundances and number of IMS bands are observed. We attribute these changes in the mobility profiles in the presence of gas-phase modifiers to a clustering/declustering mechanism by which organic molecules adsorb to the protein ion surface and lower energetic barriers for interconversion between conformational states, thus redefining the free energy landscape and equilibria between conformers. These structural biology experiments open new avenues for manipulation and interrogation of biomolecules in the gas-phase with the potential to emulate a large suite of solution conditions, ultimately including conditions that more accurately reflect a variety of intracellular environments.

biochemistry↗

bioRxiv2018

Online parallel accumulation - serial fragmentation (PASEF) with a novel trapped ion mobility mass spectrometer

In bottom-up proteomics, peptides are separated by liquid chromatography with elution peak widths in the range of seconds, while mass spectra are acquired in about 100 microseconds with time-of-fight (TOF) instruments. This allows adding ion mobility as a third dimension of separation. Among several formats, trapped ion mobility spectrometry (TIMS) is attractive due to its small size, low voltage requirements and high efficiency of ion utilization. We have recently demonstrated a scan mode termed parallel accumulation - serial fragmentation (PASEF), which multiplies the sequencing speed without any loss in sensitivity (Meier et al., PMID: 26538118). Here we introduce the timsTOF Pro instrument, which optimally implements online PASEF. It features an orthogonal ion path into the ion mobility device, limiting the amount of debris entering the instrument and making it very robust in daily operation. We investigate different precursor selection schemes for shotgun proteomics to optimally allocate in excess of 100 fragmentation events per second. More than 800,000 fragmentation spectra in standard 120 min LC runs are easily achievable, which can be used for near exhaustive precursor selection in complex mixtures or re-sequencing weak precursors. MaxQuant identified more than 6,400 proteins in single run HeLa analyses without matching to a library, and with high quantitative reproducibility (R > 0.97). Online PASEF achieves a remarkable sensitivity with more than 2,900 proteins identified in 30 min runs of only 10 ng HeLa digest. We also show that highly reproducible collisional cross sections can be acquired on a large scale (R > 0.99). PASEF on the timsTOF Pro is a valuable addition to the technological toolbox in proteomics, with a number of unique operating modes that are only beginning to be explored.

systems biology↗