54 results on '"Chow HY"'
Search Results
2. Arginine deprivation inhibits pancreatic cancer cell migration, invasion and EMT via the down regulation of Snail, Slug, Twist, and MMP1/9
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Wang, Huan, primary, Li, Qing-Fang, additional, Chow, HY, additional, Choi, SC, additional, and Leung, Yun-Chung, additional
- Published
- 2019
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3. Cultural barriers and facilitators of the parents for human papillomavirus (HPV) vaccination uptake by their daughters: A systematic review.
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Salleh NS, Abdullah KL, and Chow HY
- Abstract
Objective: There is a pressing need for public health practitioners to understand cultural values influencing parents on the uptake of human papillomavirus (HPV) vaccination for their daughters, which is presenting a growing challenge to close the immunization gap worldwide. Parental decisions were predominantly shaped by cultural norms and values. This systematic review encompasses parental perspectives on the influence of cultural values on the uptake of HPV vaccination by their daughters., Method: This systematic review was registered on PROSPERO CRD42020211324. Eligible articles were selected from CINAHL, PsycINFO, EMBASE, PubMed and Science Direct. Original qualitative studies exploring parental perspectives on the influence of cultural values on the uptake of HPV vaccination by their daughters under the age of 18, published in the English language with no restriction dates were reviewed. Two authors independently screened abstracts, conducted the fill-text review, extracted information using a standardized form, and assessed study quality. A third author is needed to resolve the disagreements if necessary., Results: Of the 1552 citations, 22 were included, with information on 639 parents. Five themes emerged from the data: sexuality-related concerns; upbringing and moral values; obligation to protect; external influences; and vaccine-related concerns., Conclusion: This systematic review is beneficial to identify and understand the culturally related facilitators and barriers to HPV vaccination among young women for the development of strategies to optimize HPV vaccine coverage among this population group by the policymakers., Competing Interests: Conflicts of interest None., (Copyright © 2024 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.)
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- 2024
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4. Prior disulfide bond-mediated Ser/Thr ligation.
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Liu H, Chow HY, Liu J, Shi P, and Li X
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In this work, we developed a novel strategy, prior disulfide bond-mediated Ser/Thr ligation (PD-STL), for the chemical synthesis of peptides and proteins. This approach combines disulfide bond-forming chemistry with Ser/Thr ligation (STL), converting intermolecular STL into intramolecular STL to effectively proceed regardless of concentrations. We demonstrated the effectiveness of PD-STL under high dilution conditions, even for the relatively inert C-terminal proline at the ligation site. Additionally, we applied this method to synthesize the N-terminal cytoplasmic domain (2-104) of caveolin-1 and its Tyr14 phosphorylated form., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)
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- 2024
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5. Drosophila adhesion GPCR Remoulade regulates axon growth, branching, and guidance by modulating Rac1 GTPase.
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Yang X, Pan C, Ye M, Liang J, Cheng H, Liang Q, Huang S, Wang J, Chow HY, and He H
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- Animals, GTP Phosphohydrolases, Axons, Drosophila, Drosophila Proteins genetics
- Abstract
Competing Interests: Conflict of interest The authors declare no conflict of interest.
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- 2024
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6. A superior heterologous prime-boost vaccination strategy against COVID-19: A bivalent vaccine based on yeast-derived RBD proteins followed by a heterologous vaccine.
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Liu Y, Li M, Cui T, Chen Z, Xu L, Li W, Peng Q, Li X, Zhao D, Valencia CA, Dong B, Wang Z, Chow HY, and Li Y
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- Animals, Mice, Vaccines, Combined, Fungal Proteins, Saccharomyces cerevisiae genetics, SARS-CoV-2, Vaccination, COVID-19 prevention & control, Vaccines
- Abstract
Various vaccines have been challenged by SARS-CoV-2 variants. Here, we reported a yeast-derived recombinant bivalent vaccine (Bivalent wild-type [Wt]+De) based on the wt and Delta receptor-binding domain (RBD). Yeast derived RBD proteins based on the wt and Delta mutant were used as the prime vaccine. It was found that, in the presence of aluminium hydroxide (Alum) and unmethylated CpG-oligodeoxynucleotides (CpG) adjuvants, more cross-protective immunity against SARS-CoV-2 prototype and variants were elicited by bivalent vaccine than monovalent wtRBD or Delta RBD. Furthermore, a heterologous boosting strategy consisting of two doses of bivalent vaccines followed by one dose adenovirus vectored vaccine exhibited cross-neutralization capacity and specific T cell responses against Delta and Omicron (BA.1 and BA.4/5) variants in mice, superior to a homologous vaccination strategy. This study suggested that heterologous prime-boost vaccination with yeast-derived bivalent protein vaccine could be a potential approach to address the challenge of emerging variants., (© 2024 The Authors. Journal of Medical Virology published by Wiley Periodicals LLC.)
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- 2024
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7. Arginine Is a Novel Drug Target for Arginine Decarboxylase in Human Colorectal Cancer Cells.
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Wei X, Chow HY, Chong HC, Leung SL, Ho MK, Lee MY, and Leung YC
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- Humans, Animals, Rats, Arginase, Arginine, Agmatine, Colonic Neoplasms
- Abstract
Colorectal cancer (CRC) has been proven to be highly reliant on arginine availability. Limiting arginine-rich foods or treating patients with arginine-depleting enzymes arginine deiminase (ADI) or arginase can suppress colon cancer. However, arginase and ADI are not the best drug candidates for CRC. Ornithine, the product of arginase, can enhance the supply of polyamine, which favors CRC cell growth, while citrulline, the product of ADI, faces the problem of arginine recycling due to the overexpression of argininosuccinate synthetase (ASS). Biosynthetic arginine decarboxylase (ADC), an enzyme that catalyzes the conversion of arginine to agmatine and carbon dioxide, may be a better choice as it combines both arginine depletion and suppression of intracellular polyamine synthesis via its product agmatine. ADC has anti-tumor potential yet has received much less attention than the other two arginine-depleting enzymes. In order to gain a better understanding of ADC, the preparation and the anti-cancer properties of this enzyme were explored in this study. When tested in vitro, ADC inhibited the proliferation of three colorectal cancer cell lines regardless of their ASS cellular expression. In contrast, ADC had a lesser cytotoxic effect on the human foreskin fibroblasts and rat primary hepatocytes. Further in vitro studies revealed that ADC induced S and G2/M phase cell-cycle arrest and apoptosis in HCT116 and LoVo cells. ADC-induced apoptosis in HCT116 cells followed the mitochondrial apoptotic pathway and was caspase-3-dependent. With all results obtained, we suggest that arginine is a potential target for treating colorectal cancer with ADC, and the anti-cancer properties of ADC should be more deeply investigated in the future.
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- 2023
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8. Enhanced sensitivity of neutralizing antibody detection for different AAV serotypes using HeLa cells with overexpressed AAVR.
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Zheng Z, Ye J, Leng M, Gan C, Tang N, Li W, Valencia CA, Dong B, and Chow HY
- Abstract
A cell-based transduction inhibition assay (TI) is widely used in clinical trials to detect neutralizing antibody (NAb) titers against recombinant adeno-associated virus (rAAV), one of the most important criteria to exclude patients in gene therapy. Different cell lines are used in cell-based TI because the rAAV transduction efficiencies vary largely among serotypes. A cell line suitable for TI for most serotypes is highly desirable, especially for those with very low transduction efficiencies in vitro such as rAAV8 and rAAV9. Herein, we report an AAVR-HeLa, a stable cell line with overexpressed AAVR, a newly identified receptor for rAAVs, was established for cell-based TIs. The AAVR expression level in AAVR-HeLa cells was approximately 10-fold higher than in HeLa cells, and was stably transfected after twenty three passages. For all AAV serotypes (AAV1-10), except for AAV4, the transduction efficiencies increased significantly in AAVR-HeLa cells. It was demonstrated that the AAVR enhancement of transduction efficiency was only for rAAV and not for lentiviral and adenoviral vectors. According to the minimal multiplicity of infection (MOIs) for the assay, the NAb detection sensitivity increased at least 10 and 20 fold for AAV8 and AAV9, respectively. The seroprevalence of NAbs were investigated at the 1:30 level as a cutoff value using AAVR-HeLa cells. It was shown that the seropositive rate for AAV2 was 87% in serum samples from 99 adults, followed by lower seropositive rates for AAV5 (7%), AAV8 (7%) and AAV9 (1%). Venn diagram analysis showed the presence of cross-reactivity of NAbs to two or three serotypes in 13 samples (13.1%). However, no patient was found to possess NAbs for all the four serotypes. These results demonstrated that the AAVR-HeLa cell line may be utilized to detect the NAbs through cell-based TI assays for most of AAV serotypes., Competing Interests: Authors BD and NT were employed by the company Sichuan Real and Best Biotech Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zheng, Ye, Leng, Gan, Tang, Li, Valencia, Dong and Chow.)
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- 2023
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9. Gossypol acetate: A natural polyphenol derivative with antimicrobial activities against the essential cell division protein FtsZ.
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Du RL, Chow HY, Chen YW, Chan PH, Daniel RA, and Wong KY
- Abstract
Antimicrobial resistance has attracted worldwide attention and remains an urgent issue to resolve. Discovery of novel compounds is regarded as one way to circumvent the development of resistance and increase the available treatment options. Gossypol is a natural polyphenolic aldehyde, and it has attracted increasing attention as a possible antibacterial drug. In this paper, we studied the antimicrobial properties (minimum inhibitory concentrations) of gossypol acetate against both Gram-positive and Gram-negative bacteria strains and dig up targets of gossypol acetate using in vitro assays, including studying its effects on functions (GTPase activity and polymerization) of Filamenting temperature sensitive mutant Z (FtsZ) and its interactions with FtsZ using isothermal titration calorimetry (ITC), and in vivo assays, including visualization of cell morphologies and proteins localizations using a microscope. Lastly, Bacterial membrane permeability changes were studied, and the cytotoxicity of gossypol acetate was determined. We also estimated the interactions of gossypol acetate with the promising target. We found that gossypol acetate can inhibit the growth of Gram-positive bacteria such as the model organism Bacillus subtilis and the pathogen Staphylococcus aureus [both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA)]. In addition, gossypol acetate can also inhibit the growth of Gram-negative bacteria when the outer membrane is permeabilized by Polymyxin B nonapeptide (PMBN). Using a cell biological approach, we show that gossypol acetate affects cell division in bacteria by interfering with the assembly of the cell division FtsZ ring. Biochemical analysis shows that the GTPase activity of FtsZ was inhibited and polymerization of FtsZ was enhanced in vitro, consistent with the block to cell division in the bacteria tested. The binding mode of gossypol acetate in FtsZ was modeled using molecular docking and provides an understanding of the compound mode of action. The results point to gossypol (S2303) as a promising antimicrobial compound that inhibits cell division by affecting FtsZ polymerization and has potential to be developed into an effective antimicrobial drug by chemical modification to minimize its cytotoxic effects in eukaryotic cells that were identified in this work., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Du, Chow, Chen, Chan, Daniel and Wong.)
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- 2023
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10. Development and Utility of a PAK1-Selective Degrader.
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Chow HY, Karchugina S, Groendyke BJ, Toenjes S, Hatcher J, Donovan KA, Fischer ES, Abalakov G, Faezov B, Dunbrack R, Gray NS, and Chernoff J
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- Animals, Mice, Dibenzazepines, Pyrrolidines
- Abstract
Overexpression of PAK1, a druggable kinase, is common in several malignancies, and inhibition of PAK1 by small molecules has been shown to impede the growth and survival of such cells. Potent inhibitors of PAKs 1-3 have been described, but clinical development has been hindered by recent findings that PAK2 function is required for normal cardiovascular function in adult mice. A unique allosteric PAK1-selective inhibitor, NVS-PAK1-1, provides a potential path forward, but has modest potency. Here, we report the development of BJG-05-039, a PAK1-selective degrader consisting of NVS-PAK1-1 conjugated to lenalidomide, a recruiter of the E3 ubiquitin ligase substrate adaptor Cereblon. BJG-05-039 induced selective degradation of PAK1 and displayed enhanced anti-proliferative effects relative to its parent compound in PAK1-dependent, but not PAK2-dependent, cell lines. Our findings suggest that selective PAK1 degradation may confer more potent pharmacological effects compared with catalytic inhibition and highlight the potential advantages of PAK1-targeted degradation.
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- 2022
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11. Studies on daptomycin lactam-based analogues.
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Chow HY, Po KHL, Chen S, and Li X
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- Lactams pharmacology, Anti-Bacterial Agents pharmacology, Anti-Bacterial Agents chemistry, Microbial Sensitivity Tests, Daptomycin pharmacology, Methicillin-Resistant Staphylococcus aureus
- Abstract
Herein, we report the synthesis and antibacterial evaluation of a series of daptomycin lactam-based analogues. As compared with daptomycin, the daptomycin analogue with singly modified lactam has an eightfold increase in its minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus. Incorporating effective modifications found in previous daptomycin structure-activity relationship studies to produce lactam-based analogues with multiple modifications did not improve the antibacterial activity of the analogues. Instead, the antibacterial activity was greatly reduced when a rather rigid 4-(phenylethynyl)benzoyl group replaced the flexible n-decanoyl group. The fact that the lactam analogue with the 4-(phenylethynyl)benzoyl group did not exhibit the antibacterial activity comparable to the two respective singly modified analogues showed that the inactivity was probably due to the deviation from the active conformation. This series of lactam analogues may generate insights on the importance of studying the active conformation of daptomycin and how the structural modifications affect the active conformation., (© 2022 European Peptide Society and John Wiley & Sons Ltd.)
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- 2022
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12. A vaccine based on the yeast-expressed receptor-binding domain (RBD) elicits broad immune responses against SARS-CoV-2 variants.
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Liu Y, Zhao D, Wang Y, Chen Z, Yang L, Li W, Gong Y, Gan C, Tang J, Zhang T, Tang D, Dong X, Yang Q, Valencia CA, Dai L, Qi S, Dong B, Chow HY, and Li Y
- Subjects
- Mice, Humans, Animals, SARS-CoV-2, Saccharomyces cerevisiae, COVID-19 Vaccines, Pandemics, Mice, Inbred BALB C, Adjuvants, Immunologic, Recombinant Proteins, Immunity, Viral Vaccines, COVID-19 prevention & control
- Abstract
Development of safe and efficient vaccines is still necessary to deal with the COVID-19 pandemic. Herein, we reported that yeast-expressed recombinant RBD proteins either from wild-type or Delta SARS-CoV-2 were able to elicit immune responses against SARS-CoV-2 and its variants. The wild-type RBD (wtRBD) protein was overexpressed in Pichia pastoris , and the purified protein was used as the antigen to immunize mice after formulating an aluminium hydroxide (Alum) adjuvant. Three immunization programs with different intervals were compared. It was found that the immunization with an interval of 28 days exhibited the strongest immune response to SARS-CoV-2 than the one with an interval of 14 or 42 days based on binding antibody and the neutralizing antibody (NAb) analyses. The antisera from the mice immunized with wtRBD were able to neutralize the Beta variant with a similar efficiency but the Delta variant with 2~2.5-fold decreased efficiency. However, more NAbs to the Delta variant were produced when the Delta RBD protein was used to immunize mice. Interestingly, the NAbs may cross react with the Omicron variant. To increase the production of NAbs, the adjuvant combination of Alum and CpG oligonucleotides was used. Compared with the Alum adjuvant alone, the NAbs elicited by the combined adjuvants exhibited an approximate 10-fold increase for the Delta and a more than 53-fold increase for the Omicron variant. This study suggested that yeast-derived Delta RBD is a scalable and an effective vaccine candidate for SARS-CoV-2 and its variants., Competing Interests: Author BD is employed by Sichuan Real & Best Biotech Co., Ltd., Chengdu, China. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Liu, Zhao, Wang, Chen, Yang, Li, Gong, Gan, Tang, Zhang, Tang, Dong, Yang, Valencia, Dai, Qi, Dong, Chow and Li.)
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- 2022
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13. Detection of SARS-CoV-2 intra-host recombination during superinfection with Alpha and Epsilon variants in New York City.
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Wertheim JO, Wang JC, Leelawong M, Martin DP, Havens JL, Chowdhury MA, Pekar JE, Amin H, Arroyo A, Awandare GA, Chow HY, Gonzalez E, Luoma E, Morang'a CM, Nekrutenko A, Shank SD, Silver S, Quashie PK, Rakeman JL, Ruiz V, Torian LV, Vasylyeva TI, Kosakovsky Pond SL, and Hughes S
- Subjects
- Genome, Viral genetics, Humans, New York City epidemiology, Recombination, Genetic, SARS-CoV-2 genetics, Spike Glycoprotein, Coronavirus genetics, COVID-19, Superinfection
- Abstract
Recombination is an evolutionary process by which many pathogens generate diversity and acquire novel functions. Although a common occurrence during coronavirus replication, detection of recombination is only feasible when genetically distinct viruses contemporaneously infect the same host. Here, we identify an instance of SARS-CoV-2 superinfection, whereby an individual was infected with two distinct viral variants: Alpha (B.1.1.7) and Epsilon (B.1.429). This superinfection was first noted when an Alpha genome sequence failed to exhibit the classic S gene target failure behavior used to track this variant. Full genome sequencing from four independent extracts reveals that Alpha variant alleles comprise around 75% of the genomes, whereas the Epsilon variant alleles comprise around 20% of the sample. Further investigation reveals the presence of numerous recombinant haplotypes spanning the genome, specifically in the spike, nucleocapsid, and ORF 8 coding regions. These findings support the potential for recombination to reshape SARS-CoV-2 genetic diversity., (© 2022. The Author(s).)
- Published
- 2022
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14. Optimization of miR-22 expression cassette for rAAV delivery on diabetes.
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Yang L, Du W, Zheng Z, Wang L, Xiao L, Yang Q, Hao Q, Zhou J, Du J, Li J, Valencia CA, Dong B, Chow HY, Fu X, and Dong B
- Abstract
MicroRNA-22 (miR-22) was suggested to be important for type 2 diabetes but its functions for this disease remained unclear. Recombinant adeno-associated virus (rAAV)-mediated miR delivery is a powerful approach to study miR functions in vivo, however, the overexpression of miR-22 by rAAV remains challenging because it is one of the most abundant miRs in the liver. In this study, a series of expression cassettes were designed and compared. It was shown that different lengths of primary miR-22 were overexpressed in HEK293 and HeLa cells but the longer ones were more efficiently expressed. miR-22 may be placed in either introns or the 3' UTR of a transgene for efficient overexpression. RNA polymerase III or II promoters were successfully utilized for miR expression but the latter showed higher expression levels in cell lines. Specifically, miR-22 was expressed efficiently together with an EGFP gene. After screening, a liver-specific TTR promoter was chosen to overexpress miR-22 in diabetic mice fed a high-fat diet. It was shown that miR-22 was overexpressed 2-3 folds which improved the insulin sensitivity significantly. The approach utilized in this study to optimize miR overexpression is a powerful tool for the creation of efficient rAAV vectors for the other miRs., (© 2022. The Author(s).)
- Published
- 2022
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15. PAK1 inhibition reduces tumor size and extends the lifespan of mice in a genetically engineered mouse model of Neurofibromatosis Type 2 (NF2).
- Author
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Hawley E, Gehlhausen J, Karchugina S, Chow HY, Araiza-Olivera D, Radu M, Smith A, Burks C, Jiang L, Li X, Bessler W, Masters A, Edwards D, Burgin C, Jones D, Yates C, Clapp DW, Chernoff J, and Park SJ
- Subjects
- Animals, Cell Proliferation drug effects, Cell Survival drug effects, Disease Models, Animal, Genes, Tumor Suppressor drug effects, Indoles, Longevity, Mice, Neurilemmoma genetics, Neurofibromatosis 2 metabolism, Neurofibromin 2 genetics, Phosphorylation, Piperidines, Pyrimidines, Schwann Cells metabolism, p21-Activated Kinases genetics, Neurofibromatosis 2 genetics, p21-Activated Kinases metabolism
- Abstract
Neurofibromatosis Type II (NF2) is an autosomal dominant cancer predisposition syndrome in which germline haploinsufficiency at the NF2 gene confers a greatly increased propensity for tumor development arising from tissues of neural crest derived origin. NF2 encodes the tumor suppressor, Merlin, and its biochemical function is incompletely understood. One well-established function of Merlin is as a negative regulator of group A serine/threonine p21-activated kinases (PAKs). In these studies we explore the role of PAK1 and its closely related paralog, PAK2, both pharmacologically and genetically, in Merlin-deficient Schwann cells and in a genetically engineered mouse model (GEMM) that develops spontaneous vestibular and spinal schwannomas. We demonstrate that PAK1 and PAK2 are both hyper activated in Merlin-deficient murine schwannomas. In preclinical trials, a pan Group A PAK inhibitor, FRAX-1036, transiently reduced PAK1 and PAK2 phosphorylation in vitro, but had insignificant efficacy in vivo. NVS-PAK1-1, a PAK1 selective inhibitor, had a greater but still minimal effect on our GEMM phenotype. However, genetic ablation of Pak1 but not Pak2 reduced tumor formation in our NF2 GEMM. Moreover, germline genetic deletion of Pak1 was well tolerated, while conditional deletion of Pak2 in Schwann cells resulted in significant morbidity and mortality. These data support the further development of PAK1-specific small molecule inhibitors and the therapeutic targeting of PAK1 in vestibular schwannomas and argue against PAK1 and PAK2 existing as functionally redundant protein isoforms in Schwann cells., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)
- Published
- 2021
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16. An atomic perspective on improving daptomycin's activity.
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Blasco P, Zhang C, Chow HY, Chen G, Wu Y, and Li X
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- Anti-Bacterial Agents chemistry, Anti-Bacterial Agents metabolism, Depsipeptides chemistry, Depsipeptides metabolism, Lipopeptides chemistry, Lipopeptides metabolism, Calcium chemistry, Calcium metabolism, Daptomycin chemistry, Daptomycin metabolism, Molecular Dynamics Simulation
- Abstract
Background: Recently, through comprehensive medicinal chemistry efforts, we have found a new daptomycin analogue, termed kynomycin, showing enhanced activity against both methicillin-resistant S. aureus and vancomycin-resistant Enterococcus in vitro and in vivo, with improved pharmacokinetics and lower cytotoxicity than daptomycin., Methods: In this study we compared the physicochemical properties of kynomycin with those of daptomycin from an atomic perspective by using Nuclear Magnetic Resonance spectroscopy and Molecular Dynamics simulations., Results and Conclusion: We observed that kynurenine methylation changes daptomycin's key physicochemical properties; its calcium dependent oligomerization efficiency is improved and the modified kynurenine strengths contacts with the lipid tail and tryptophan residues. In addition, it is observed that, compared to daptomycin, kynomycin tetramer is more stable and binds stronger to calcium. The combined experiments provide key clues for the improved antibacterial activity of kynomycin., General Significance: We expect that this approach will help study the calcium binding and oligomerization features of new calcium dependent peptide antibiotics., (Copyright © 2021 Elsevier B.V. All rights reserved.)
- Published
- 2021
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17. Evaluation of a Combined Multilocus Sequence Typing and Whole-Genome Sequencing Two-Step Algorithm for Routine Typing of Clostridioides difficile .
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Kamboj M, McMillen T, Syed M, Chow HY, Jani K, Aslam A, Brite J, Fanelli B, Hasan NA, Dadlani M, Westblade L, Zehir A, Simon M, and Babady NE
- Subjects
- Algorithms, Humans, Multilocus Sequence Typing, New York City, Clostridioides, Clostridioides difficile genetics
- Abstract
Multilocus sequence typing (MLST) is a low-resolution but rapid genotyping method for Clostridioides difficile Whole-genome sequencing (WGS) has emerged as the new gold standard for C. difficile typing, but cost and lack of standardization still limit broad utilization. In this study, we evaluated the potential to combine the portability of MLST with the increased resolution of WGS for a cost-saving approach to routine C. difficile typing. C. difficile strains from two New York City hospitals (hospital A and hospital B) were selected. WGS single-nucleotide polymorphism (wgSNP) was performed using established methods. Sequence types (ST) were determined using PubMLST, while wgSNP analysis was performed using the Bionumerics software. An additional analysis of a subset of data (hospital A) was made comparing the Bionumerics software to the CosmosID pipeline. Cost and turnaround time to results were compared for the algorithmic approach of MLST followed by wgSNP versus direct wgSNP. Among the 202 C. difficile isolates typed, 91% ( n = 185/203) clustered within the representative ST, showing a high agreement between MLST and wgSNP. While clustering was similar between the Bionumerics and CosmosID pipelines, large differences in the overall number of SNPs were noted. A two-step algorithm for routine typing results in significantly lower cost than routine use of WGS. Our results suggest that using MLST as a first step in routine typing of C. difficile followed by WGS for MLST concordant strains is a less technically demanding, cost-saving approach for performing C. difficile typing than WGS alone without loss of discriminatory power., (Copyright © 2021 American Society for Microbiology.)
- Published
- 2021
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18. Mutant TP53 interacts with BCAR1 to contribute to cancer cell invasion.
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Guo AK, Itahana Y, Seshachalam VP, Chow HY, Ghosh S, and Itahana K
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- Cell Line, Tumor, Humans, Mutation, Crk-Associated Substrate Protein metabolism, Neoplasm Invasiveness genetics, Tumor Suppressor Protein p53 genetics, Tumor Suppressor Protein p53 metabolism
- Abstract
Background: Mutant TP53 interacts with other proteins to produce gain-of-function properties that contribute to cancer metastasis. However, the underlying mechanisms are still not fully understood., Methods: Using immunoprecipitation and proximity ligation assays, we evaluated breast cancer anti-estrogen resistance 1 (BCAR1) as a novel binding partner of TP53
R273H , a TP53 mutant frequently found in human cancers. The biological functions of their binding were examined by the transwell invasion assay. Clinical outcome of patients was analysed based on TP53 status and BCAR1 expression using public database., Results: We discovered a novel interaction between TP53R273H and BCAR1. We found that BCAR1 translocates from the cytoplasm into the nucleus and binds to TP53R273H in a manner dependent on SRC family kinases (SFKs), which are known to enhance metastasis. The expression of full-length TP53R273H , but not the BCAR1 binding-deficient mutant TP53R273H Δ102-207, promoted cancer cell invasion. Furthermore, among the patients with mutant TP53, high BCAR1 expression was associated with a poorer prognosis., Conclusions: The interaction between TP53R273H and BCAR1 plays an important role in enhancing cancer cell invasion. Thus, our study suggests a disruption of the TP53R273H -BCAR1 binding as a potential therapeutic approach for TP53R273H -harbouring cancer patients.- Published
- 2021
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19. Development of DHQ-based chemical biology probe to profile cellular targets for HBV.
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Zhang Q, Huang J, Chow HY, Wang J, Zhang Y, Fung YME, Ren Q, and Li X
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- Antiviral Agents chemical synthesis, Chromatography, Liquid, Click Chemistry, Molecular Structure, Photoaffinity Labels chemical synthesis, Proteome analysis, Proteome chemistry, Proteomics, Quinolizines chemical synthesis, Structure-Activity Relationship, Tandem Mass Spectrometry, Viral Proteins chemistry, Antiviral Agents pharmacology, Hepatitis B virus drug effects, Photoaffinity Labels pharmacology, Quinolizines pharmacology, Viral Proteins analysis
- Abstract
Chronic hepatitis B virus (HBV) infection has been a serious public health burden worldwide. Current anti-HBV therapies could not eliminate HBV ultimately. Considering the characteristics of HBV, it is impossible to be entirely cured based on current therapies. Therefore, it is urgently needed to develop novel therapeutic agents with new mechanism of action. The dihydroquinolizinone (DHQ) derivatives exhibited potent anti-HBV activity by decreasing HBV DNA and HBsAg level in an obscure mechanism of action. In this study, we have optimized the DHQ scaffold, developed the photoaffinity probe, with which to identify potential binding proteins., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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20. Recombinant Bacillus caldovelox Arginase Mutant (BCA-M) Induces Apoptosis, Autophagy, Cell Cycle Arrest and Growth Inhibition in Human Cervical Cancer Cells.
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Chung SF, Kim CF, Chow HY, Chong HC, Tam SY, Leung YC, and Lo WH
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- Arginase genetics, Cell Line, Tumor, Cell Proliferation drug effects, Drug Synergism, Female, Gene Expression Profiling, Geobacillus genetics, Humans, Metabolic Networks and Pathways drug effects, Mutant Proteins, Recombinant Proteins genetics, Urea metabolism, Uterine Cervical Neoplasms drug therapy, Uterine Cervical Neoplasms genetics, Uterine Cervical Neoplasms metabolism, Uterine Cervical Neoplasms pathology, Antineoplastic Agents pharmacology, Apoptosis drug effects, Arginase pharmacology, Autophagy drug effects, Cell Cycle Checkpoints drug effects, Geobacillus enzymology, Recombinant Proteins pharmacology
- Abstract
With our recent success in developing a recombinant human arginase drug against broad-spectrum cancer cell lines, we have explored the potential of a recombinant Bacillus caldovelox arginase mutant (BCA-M) for human cervical cancer treatment. Our studies demonstrated that BCA-M significantly inhibited the growth of human cervical cancer cells in vitro regardless of argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) expression. Drug susceptibilities correlate well with the expressions of major urea cycle genes and completeness of L-arginine regeneration pathways. With the expressions of ASS and ASL genes conferring resistance to L-arginine deiminase (ADI) which is undergoing Phase III clinical trial, BCA-M offers the advantage of a broader spectrum of susceptible cancer cells. Mechanistic studies showed that BCA-M inhibited the growth of human cervical cancer cells by inducing apoptosis and cell cycle arrest at S and/or G
2 /M phases. Our results also displayed that autophagy served as a protective mechanism, while the growth inhibitory effects of BCA-M could be enhanced synergistically by its combination to the autophagy inhibitor, chloroquine (CQ), on human cervical cancer cells.- Published
- 2020
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21. The Effect of Conduction Exercise and Self-Acupressure in Treatment of Parkinson's Disease: A Pilot Study.
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Yuen CS, Chua KK, Lau WH, Zhuang ZY, Chow HY, and Li M
- Abstract
Introduction: Parkinson's disease cannot be well treated by conventional medication. Acupuncture and Tai Chi are proven to be effective in relieving symptoms of Parkinson's disease. Traditional Chinese medicine exercises may prove to be an effective complementary therapy., Objective: To evaluate the efficacy and safety of conduction exercise and self-acupressure in treating Parkinson's disease., Method: This study is an accessor- and data analyzer-blind, add-on, randomized, controlled, pilot clinical study. In the treatment group, they were taught to practice conduction exercise and self-acupressure for 8 weeks. No additional treatment was given in the control group. Assessments were done at week 4 and week 8 of the treatment period. The primary outcomes are the total score and domain scores of the Chinese version of 39-item Parkinson's Disease Questionnaire. The secondary outcomes are the total score and domain scores of a custom-designed questionnaire, which is a short form of Nonmotor Symptom Scale., Results: 22 patients in the treatment group and 14 in the control group continued to the treatment phase. Patients in the treatment group displayed improvement trends in primary and secondary outcomes. Improvements were significant in two areas of a custom-designed questionnaire: total score ( p =0.014) and domain score of gastrointestinal tract ( p =0.004). No severe adverse events were reported., Conclusion: Conduction exercise and self-acupressure were well accepted by and feasible for Parkinson's disease patients. The data generated can be used for the planning of future studies. The exercise regime can be promoted as a home-based, self-practice therapy for Parkinson's disease patients, due to its safety, low cost, and convenience in implementation. This study is registered with the Chinese Clinical Trial Registry (ChiCTR-IPR-17011987, on 14 July 2017)., Competing Interests: The authors declare that they have no competing interests regarding the publication of this paper., (Copyright © 2020 Chun-Sum Yuen et al.)
- Published
- 2020
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22. Establishing the Structure-Activity Relationship of Daptomycin.
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Chow HY, Po KHL, Jin K, Qiao G, Sun Z, Ma W, Ye X, Zhou N, Chen S, and Li X
- Abstract
Daptomycin is effective in treating infections caused by antibiotic-resistant Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE), and vancomycin-resistant S. aureus (VRSA). Due to its distinct mechanism of action toward multidrug-resistant bacteria, daptomycin provides an attractive structural motif to generate new daptomycin-based antibiotics to combat the problem of bacterial resistance. In this study, we used the total synthesis method to produce daptomycin analogues with a variety in terms of types and sites of modifications. Five classes of daptomycin analogues were synthesized, and the antimicrobial activities of the analogues were analyzed by several biological assays. From this study, we established a comprehensive structure-activity relationship of daptomycin which will lay the foundation for the further development of daptomycin-based antibiotics., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)
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- 2020
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23. Improved total synthesis of the antibiotic A54145B.
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Chow HY, Chen D, and Li X
- Abstract
A54145B is a calcium-dependent cyclic lipodepsipeptide antibiotic that is active against Gram-positive pathogens. Herein, we report an improved synthetic route toward A54145B in terms of the yield and time required. The key changes include using a pre-assembled minimalist tetradepsipeptide building block to solve the difficult on-resin esterification from our previous synthetic route, and a new macrocyclization site to avoid the peptide self-cleavage problem.
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- 2020
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24. Enhanced Activity against Multidrug-Resistant Bacteria through Coapplication of an Analogue of Tachyplesin I and an Inhibitor of the QseC/B Signaling Pathway.
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Yu R, Wang J, So LY, Harvey PJ, Shi J, Liang J, Dou Q, Li X, Yan X, Huang YH, Xu Q, Kaas Q, Chow HY, Wong KY, Craik DJ, Zhang XH, Jiang T, and Wang Y
- Subjects
- Amino Acid Sequence, Anti-Bacterial Agents chemical synthesis, Antimicrobial Cationic Peptides chemical synthesis, Bacterial Proteins metabolism, Cell Line, Cell Membrane metabolism, DNA-Binding Proteins chemical synthesis, Drug Resistance, Multiple, Bacterial drug effects, Drug Stability, Drug Synergism, Humans, Male, Microbial Sensitivity Tests, Molecular Dynamics Simulation, Peptides, Cyclic chemical synthesis, Stereoisomerism, Sulfonamides pharmacology, Anti-Bacterial Agents pharmacology, Antimicrobial Cationic Peptides pharmacology, Bacteria drug effects, DNA-Binding Proteins pharmacology, Peptides, Cyclic pharmacology, Signal Transduction drug effects
- Abstract
Tachyplesin I (TPI) is a cationic β-hairpin antimicrobial peptide with broad-spectrum, potent antimicrobial activity. In this study, the all d-amino acid analogue of TPI (TPAD) was synthesized, and its structure and activity were determined. TPAD has comparable antibacterial activity to TPI on 14 bacterial strains, including four drug-resistant bacteria. Importantly, TPAD has significantly improved stability against enzymatic degradation and decreased hemolytic activity compared to TPI, indicating that it has better therapeutic potential. The induction of bacterial resistance using low concentrations of TPAD resulted in the activation of the QseC/B two-component system. Deletion of this system resulted in at least five-fold improvement of TPAD activity, and the combined use of TPAD with LED209, a QseC/B inhibitor, significantly enhanced the bactericidal effect against three classes of multidrug-resistant bacteria.
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- 2020
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25. Methylation of Daptomycin Leading to the Discovery of Kynomycin, a Cyclic Lipodepsipeptide Active against Resistant Pathogens.
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Chow HY, Po KHL, Gao P, Blasco P, Wang X, Li C, Ye L, Jin K, Chen K, Chan EWC, You X, Yi Tsun Kao R, Chen S, and Li X
- Subjects
- Animals, Anti-Bacterial Agents chemical synthesis, Anti-Bacterial Agents pharmacokinetics, Anti-Bacterial Agents toxicity, Cell Membrane Permeability drug effects, Daptomycin chemistry, Daptomycin therapeutic use, Depsipeptides chemical synthesis, Depsipeptides pharmacokinetics, Depsipeptides toxicity, Drug Resistance, Bacterial drug effects, Enterococcus drug effects, Female, HEK293 Cells, Humans, Lepidoptera drug effects, Lepidoptera microbiology, Lipopeptides chemical synthesis, Lipopeptides pharmacokinetics, Lipopeptides toxicity, Male, Methicillin-Resistant Staphylococcus aureus drug effects, Methylation, Mice, Inbred BALB C, Mice, Inbred ICR, Microbial Sensitivity Tests, Anti-Bacterial Agents therapeutic use, Depsipeptides therapeutic use, Lipopeptides therapeutic use, Staphylococcal Infections drug therapy
- Abstract
Increased usage of daptomycin to treat infections caused by Gram-positive bacterial pathogens has resulted in emergence of resistant mutants. In a search for more effective daptomycin analogues through medicinal chemistry studies, we found that methylation at the nonproteinogenic amino acid kynurenine in daptomycin could result in significant enhancement of antibacterial activity. Termed "kynomycin," this new antibiotic exhibits higher antibacterial activity than daptomycin and is able to eradicate methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus ( VRE) strains, including daptomycin-resistant strains. The improved antimicrobial activity of kynomycin was demonstrated in in vitro time-killing assay, in vivo wax worm model, and different mouse infection models. The increased antibacterial activity, improved pharmacokinetics, and lower cytotoxicity of kynomycin, compared to daptomycin, showed the promise of the future design and development of next-generation daptomycin-based antibiotics.
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- 2020
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26. OPA-Based Bifunctional Linker for Protein Labeling and Profiling.
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Zhang Q, Zhang Y, Liu H, Chow HY, Tian R, Eva Fung YM, and Li X
- Subjects
- Alkynes chemical synthesis, Animals, Bacteria chemistry, Chickens, Molecular Probes chemical synthesis, o-Phthalaldehyde chemical synthesis, Alkynes chemistry, Lysine chemistry, Molecular Probes chemistry, Proteins chemistry, o-Phthalaldehyde analogs & derivatives
- Abstract
Lysine residues have been considered as a routine conjugating site for protein chemical labeling and modification. The commercially available lysine-labeling agents have several limitations in labeling efficiency, stability, and cost. To pursue alternative protein lysine-labeling strategies, herein, we report the development of an ortho -phthalaldehyde (OPA)-based bifunctional linker suitable for protein chemical labeling and profiling. Among three designed OPA-based bifunctional linkers, OPA-NH-alkyne 5 was proved to be optimal for protein labeling with minimal protein turbidity. We further demonstrated OPA-NH-alkyne 5 was applicable for immediate capture of protein or proteome chemical labeling.
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- 2020
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27. PEGylated recombinant human arginase as a drug for breast cancer.
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Leung SL, Ho MK, Lam YM, Chow HY, So YH, and Leung YC
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- Animals, Antineoplastic Agents administration & dosage, Antineoplastic Agents chemistry, Arginase administration & dosage, Arginase chemistry, Breast Neoplasms pathology, Cell Line, Tumor, Female, Humans, Mice, Mice, Inbred BALB C, Mice, Nude, Recombinant Proteins, Xenograft Model Antitumor Assays, Antineoplastic Agents pharmacology, Arginase pharmacology, Breast Neoplasms drug therapy, Polyethylene Glycols chemistry
- Published
- 2019
28. Ligation Technologies for the Synthesis of Cyclic Peptides.
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Chow HY, Zhang Y, Matheson E, and Li X
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- Amino Acid Sequence, Animals, Bacteria chemistry, Chemistry Techniques, Synthetic methods, Cyclization, Humans, Plants chemistry, Peptides, Cyclic chemical synthesis
- Abstract
Cyclic peptides have been attracting a lot of attention in recent decades, especially in the area of drug discovery, as more and more naturally occurring cyclic peptides with diverse biological activities have been discovered. Chemical synthesis of cyclic peptides is essential when studying their structure-activity relationships. Conventional peptide cyclization methods via direct coupling have inherent limitations, like the susceptibility to epimerization at the C-terminus, poor solubility of fully protected peptide precursors, and low yield caused by oligomerization. In this regard, chemoselective ligation-mediated cyclization methods have emerged as effective strategies for cyclic peptide synthesis. The toolbox for cyclic peptide synthesis has been expanded substantially in the past two decades, allowing more efficient synthesis of cyclic peptides with various scaffolds and modifications. This Review will explore different chemoselective ligation technologies used for cyclic peptide synthesis that generate both native and unnatural peptide linkages. The practical issues and limitations of different methods will be discussed. The advance in cyclic peptide synthesis will benefit the biological and medicinal study of cyclic peptides, an important class of macrocycles with potentials in numerous fields, notably in therapeutics.
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- 2019
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29. Total Synthesis and Structural Establishment/Revision of Antibiotics A54145.
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Chen D, Chow HY, Po KHL, Ma W, Leung ELY, Sun Z, Liu M, Chen S, and Li X
- Subjects
- Chemistry Techniques, Synthetic, Lipoproteins chemical synthesis, Lipoproteins chemistry, Microbial Sensitivity Tests, Anti-Bacterial Agents chemical synthesis, Anti-Bacterial Agents chemistry
- Abstract
A54145 is a family of antibacterial cyclic lipodepsipeptides structurally resembling daptomycin. Since its discovery in 1990, only the ambiguous structures of the methoxy-aspartic acid (MeO-Asp) and the hydroxy-asparagine (HO-Asn) have been reported. We have developed efficient routes to obtain the fully protected l-MeO-Asp and l-HO-Asn building blocks compatible with Fmoc-SPPS, and a total synthesis of A54145 that enabled us to establish its structure, consisting of l-3 S -HO-Asn and l-3 R -MeO-Asp, revising the wrongly proposed structure of l-3 S -MeO-Asp.
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- 2019
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30. Evaluation of the Aries Bordetella Assay for Detection and Identification of Bordetella pertussis in Nasopharyngeal Swab Specimens.
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McMillen T, Chow HY, Das S, Dunbar SA, and Babady NE
- Subjects
- Cross Reactions, DNA, Bacterial genetics, Humans, Reproducibility of Results, Retrospective Studies, Time and Motion Studies, Whooping Cough microbiology, Bordetella pertussis isolation & purification, Molecular Diagnostic Techniques methods, Nasopharynx virology, Oligonucleotide Array Sequence Analysis methods, Whooping Cough diagnosis
- Abstract
The Aries Bordetella assay (Aries BA) (Luminex Corporation) recently received FDA clearance for the detection and differentiation of Bordetella pertussis and Bordetella parapertussis nucleic acids in nasopharyngeal swab (NPS) samples. The objective of this study was to evaluate the performance of the Aries BA in comparison to that of the BioFire FilmArray respiratory panel (RP). The Aries BA was evaluated using retrospective, remnant nasopharyngeal swabs (NPS), previously tested by FilmArray RP. Performance characteristics evaluated included positive percent agreement (PPA) and negative percent agreement (NPA) with the FilmArray RP. Discordant analysis was performed using bidirectional sequencing. A time and motion study was performed to compare the laboratory workflow of the two tests. Three hundred samples were included in the study. There were no samples positive for B. parapertussis The PPA and NPA of the Aries BA were 61.1% (95% confidence interval [CI], 35.8 to 82.7%) and 100% (95% CI, 98.7 to 100%). Discordant results included five Bordetella bronchiseptica results that were incorrectly identified as B. pertussis by the FilmArray RP and one false-negative result for both the Aries BA and the FilmArray RP. The overall agreement between the Aries BA and FilmArray RP for the detection of B. pertussis was considered good at 97.7% with a kappa value of 0.71 (95% CI, 0.51 to 0.9). The Aries BA offers a new diagnostic option for the rapid and targeted approach to the diagnosis of pertussis. Unlike the FilmArray RP, the Aries BA did not cross-react with B. bronchiseptica in our study, although a larger sample set should be tested to confirm this finding., (Copyright © 2019 American Society for Microbiology.)
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- 2019
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31. Intrinsic Cleavage of RNA Polymerase II Adopts a Nucleobase-independent Mechanism Assisted by Transcript Phosphate.
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Ka Man Tse C, Xu J, Xu L, Sheong FK, Wang S, Chow HY, Gao X, Li X, Cheung PP, Wang D, Zhang Y, and Huang X
- Abstract
RNA polymerase II (Pol II) utilises the same active site for polymerization and intrinsic cleavage. Pol II proofreads the nascent transcript by its intrinsic nuclease activity to maintain high transcriptional fidelity critical for cell growth and viability. The detailed catalytic mechanism of intrinsic cleavage remains unknown. Here, we combined ab initio quantum mechanics/molecular mechanics studies and biochemical cleavage assays to show that Pol II utilises downstream phosphate oxygen to activate the attacking nucleophile in hydrolysis, while the newly formed 3'-end is protonated through active-site water without a defined general acid. Experimentally, alteration of downstream phosphate oxygen either by 2'-5' sugar linkage or stereo-specific thio-substitution of phosphate oxygen drastically reduced cleavage rate. We showed by N7-modification that guanine nucleobase does not directly involve as acid-base catalyst. Our proposed mechanism provides important insights into the understanding of intrinsic transcriptional cleavage reaction, an essential step of transcriptional fidelity control., Competing Interests: Competing interests The authors declare no competing interests
- Published
- 2019
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32. Effectiveness of ultraviolet disinfection in reducing hospital-acquired Clostridium difficile and vancomycin-resistant Enterococcus on a bone marrow transplant unit.
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Brite J, McMillen T, Robilotti E, Sun J, Chow HY, Stell F, Seo SK, McKenna D, Eagan J, Montecalvo M, Chen D, Sepkowitz K, and Kamboj M
- Subjects
- Bone Marrow Transplantation, Clostridioides difficile isolation & purification, Clostridioides difficile radiation effects, Colony Count, Microbial, Humans, Interrupted Time Series Analysis, New York, Patients' Rooms, Vancomycin-Resistant Enterococci isolation & purification, Vancomycin-Resistant Enterococci radiation effects, Clostridium Infections prevention & control, Cross Infection prevention & control, Disinfection methods, Gram-Positive Bacterial Infections prevention & control, Ultraviolet Rays
- Abstract
Objective: To determine the effectiveness of ultraviolet (UV) environmental disinfection system on rates of hospital-acquired vancomycin-resistant enterococcus (VRE) and Clostridium difficile., Design: Using active surveillance and an interrupted time-series design, hospital-acquired acquisition of VRE and C. difficile on a bone marrow transplant (BMT) unit were examined before and after implementation of terminal disinfection with UV on all rooms regardless of isolation status of patients. The main outcomes were hospital-based acquisition measured through (1) active surveillance: admission, weekly, and discharge screening for VRE and toxigenic C. difficile (TCD) and (2) clinical surveillance: incidence of VRE and CDI on the unit., Setting: Bone marrow transplant unit at a tertiary-care cancer center.ParticipantsStem cell transplant (SCT) recipients.InterventionTerminal disinfection of all rooms with UV regardless of isolation status of patients., Results: During the 20-month study period, 579 patients had 704 admissions to the BMT unit, and 2,160 surveillance tests were performed. No change in level or trend in the incidence of VRE (trend incidence rate ratio [IRR], 0.96; 95% confidence interval [CI], 0.81-1.14; level IRR, 1.34; 95% CI, 0.37-1.18) or C. difficile (trend IRR, 1.08; 95% CI, 0.89-1.31; level IRR, 0.51; 95% CI, 0.13-2.11) was observed after the intervention., Conclusions: Utilization of UV disinfection to supplement routine terminal cleaning of rooms was not effective in reducing hospital-acquired VRE and C. difficile among SCT recipients.
- Published
- 2018
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33. Group I Paks are essential for epithelial- mesenchymal transition in an Apc-driven model of colorectal cancer.
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Chow HY, Dong B, Valencia CA, Zeng CT, Koch JN, Prudnikova TY, and Chernoff J
- Subjects
- Adenomatous Polyposis Coli genetics, Animals, Apoptosis genetics, Apoptosis physiology, Cell Proliferation genetics, Cell Proliferation physiology, Colorectal Neoplasms genetics, Epithelial-Mesenchymal Transition genetics, Female, Gene Expression Regulation, Neoplastic, Humans, Mice, Proto-Oncogene Proteins p21(ras) genetics, Proto-Oncogene Proteins p21(ras) metabolism, Tumor Cells, Cultured, Wnt Signaling Pathway genetics, Wnt Signaling Pathway physiology, p21-Activated Kinases genetics, p21-Activated Kinases metabolism, Adenomatous Polyposis Coli metabolism, Colorectal Neoplasms metabolism, Epithelial-Mesenchymal Transition physiology
- Abstract
p21-activated kinases (Paks) play an important role in oncogenic signaling pathways and have been considered as potential therapeutic targets in various cancers. Most studies of Pak function employ gene knock-out or knock-down methods, but these approaches result in loss of both enzymatic and scaffolding properties of these proteins, and thus may not reflect the effects of small molecule inhibitors. Here we use a transgenic mouse model in which a specific peptide inhibitor of Group I Paks is conditionally expressed in response to Cre recombinase. Using this model, we show that inhibition of endogenous Paks impedes the transition of adenoma to carcinoma in an Apc-driven mouse model of colorectal cancer. These effects are mediated by inhibition of Wnt signaling through reduced β-catenin activity as well as suppression of an epithelial-mesenchymal transition program mediated by miR-200 and Snai1. These results highlight the potential therapeutic role of Pak1 inhibitors in colorectal cancer.
- Published
- 2018
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34. Influences of disulfide connectivity on structure and antimicrobial activity of tachyplesin I.
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Shi J, So LY, Chen F, Liang J, Chow HY, Wong KY, Wan S, Jiang T, and Yu R
- Subjects
- Amino Acid Sequence genetics, Anti-Infective Agents pharmacology, Antimicrobial Cationic Peptides genetics, Antimicrobial Cationic Peptides pharmacology, Circular Dichroism, DNA-Binding Proteins genetics, DNA-Binding Proteins pharmacology, Disulfides chemistry, Gram-Positive Bacteria pathogenicity, Microbial Sensitivity Tests, Molecular Dynamics Simulation, Peptides, Cyclic genetics, Peptides, Cyclic pharmacology, Protein Conformation drug effects, Protein Structure, Secondary, Structure-Activity Relationship, Anti-Infective Agents chemistry, Antimicrobial Cationic Peptides chemistry, DNA-Binding Proteins chemistry, Gram-Positive Bacteria drug effects, Peptides, Cyclic chemistry
- Abstract
Tachyplesin I is a potent antimicrobial peptide with broad spectrum of antimicrobial activity. It has 2 disulfide bonds and can form 3 disulfide bond isomers. In this study, the structure and antimicrobial activity of 3 tachyplesin I isomers (tachyplesin I, 3C12C, 3C7C) were investigated using molecular dynamic simulations, circular dichroism structural study, as well as antimicrobial activity and hemolysis assay. Our results suggest that in comparison to the native peptide, the 2 isomers (3C12C, 3C7C) have substantial structural and activity variations. The native peptide is in the ribbon conformation, while 3C12C and 3C7C possess remarkably different secondary structures, which are referred as "globular" and "beads" isomers, respectively. The substantially decreased hemolysis effects for these 2 isomers is accompanied by significantly decreased anti-gram-positive bacterial activity., (Copyright © 2018 European Peptide Society and John Wiley & Sons, Ltd.)
- Published
- 2018
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35. P-B Desulfurization: An Enabling Method for Protein Chemical Synthesis and Site-Specific Deuteration.
- Author
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Jin K, Li T, Chow HY, Liu H, and Li X
- Subjects
- Deuterium chemistry, Indicators and Reagents chemistry, Peptides chemistry, Protein Processing, Post-Translational, Proteins chemical synthesis, Sulfur chemistry
- Abstract
Cysteine-mediated native chemical ligation is a powerful method for protein chemical synthesis. Herein, we report an unprecedentedly mild system (TCEP/NaBH
4 or TCEP/LiBEt3 H; TCEP=tris(2-carboxyethyl)phosphine) for chemoselective peptide desulfurization to achieve effective protein synthesis via the native chemical ligation-desulfurization approach. This method, termed P-B desulfurization, features usage of common reagents, simplicity of operation, robustness, high yields, clean conversion, and versatile functionality compatibility with complex peptides/proteins. In addition, this method can be used for incorporating deuterium into the peptides after cysteine desulfurization by running the reaction in D2 O buffer. Moreover, this method enables the clean desulfurization of peptides carrying post-translational modifications, such as phosphorylation and crotonylation. The effectiveness of this method has been demonstrated by the synthesis of the cyclic peptides dichotomin C and E and synthetic proteins, including ubiquitin, γ-synuclein, and histone H2A., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
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36. Qualitative and quantitative assessment of Illumina's forensic STR and SNP kits on MiSeq FGx™.
- Author
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Sharma V, Chow HY, Siegel D, and Wurmbach E
- Subjects
- DNA Fingerprinting methods, DNA Fingerprinting standards, Female, Forensic Genetics standards, High-Throughput Nucleotide Sequencing standards, Humans, Male, Qualitative Research, Reagent Kits, Diagnostic, Reproducibility of Results, Forensic Genetics methods, High-Throughput Nucleotide Sequencing methods, Microsatellite Repeats, Polymorphism, Single Nucleotide
- Abstract
Massively parallel sequencing (MPS) is a powerful tool transforming DNA analysis in multiple fields ranging from medicine, to environmental science, to evolutionary biology. In forensic applications, MPS offers the ability to significantly increase the discriminatory power of human identification as well as aid in mixture deconvolution. However, before the benefits of any new technology can be employed, a thorough evaluation of its quality, consistency, sensitivity, and specificity must be rigorously evaluated in order to gain a detailed understanding of the technique including sources of error, error rates, and other restrictions/limitations. This extensive study assessed the performance of Illumina's MiSeq FGx MPS system and ForenSeq™ kit in nine experimental runs including 314 reaction samples. In-depth data analysis evaluated the consequences of different assay conditions on test results. Variables included: sample numbers per run, targets per run, DNA input per sample, and replications. Results are presented as heat maps revealing patterns for each locus. Data analysis focused on read numbers (allele coverage), drop-outs, drop-ins, and sequence analysis. The study revealed that loci with high read numbers performed better and resulted in fewer drop-outs and well balanced heterozygous alleles. Several loci were prone to drop-outs which led to falsely typed homozygotes and therefore to genotype errors. Sequence analysis of allele drop-in typically revealed a single nucleotide change (deletion, insertion, or substitution). Analyses of sequences, no template controls, and spurious alleles suggest no contamination during library preparation, pooling, and sequencing, but indicate that sequencing or PCR errors may have occurred due to DNA polymerase infidelities. Finally, we found utilizing Illumina's FGx System at recommended conditions does not guarantee 100% outcomes for all samples tested, including the positive control, and required manual editing due to low read numbers and/or allele drop-in. These findings are important for progressing towards implementation of MPS in forensic DNA testing.
- Published
- 2017
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37. Systematic assessment of the performance of illumina's MiSeq FGx™ forensic genomics system.
- Author
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Almalki N, Chow HY, Sharma V, Hart K, Siegel D, and Wurmbach E
- Subjects
- Alleles, Electrophoresis, Capillary methods, Female, Forensic Genetics, Genetic Variation, Humans, Male, Polymerase Chain Reaction methods, Sensitivity and Specificity, Sequence Analysis, DNA analysis, DNA Fingerprinting methods
- Abstract
This study assesses the performance of Illumina's MiSeq FGx System for forensic genomics by systematically analyzing single source samples, evaluating concordance, sensitivity and repeatability, as well as describing the quality of the reported outcomes. DNA from 16 individuals (9 males/7 females) in nine separate runs showed consistent STR profiles at DNA input ≥400 pg, and two full profiles were obtained with 50 pg DNA input. However, this study revealed that the outcome of a single sample does not merely depend on its DNA input but is also influenced by the total amount of DNA loaded onto the flow cell from all samples. Stutter and sequence or amplification errors can make the identification of true alleles difficult, particularly for heterozygous loci that show allele imbalance. Sequencing of 16 individuals' STRs revealed genetic variations at 14 loci at frequencies suggesting improvement of mixture deconvolution. The STR loci D1S1656 and DXS10103 were most susceptible to drop outs, and D22S1045 and DYS385a-b showed heterozygote imbalance. Most stutters were typed at TH01 and DYS385a-b, while amplification or sequencing errors were observed mostly at D7S820 and D19S433. Overall, Illumina's MiSeq FGx System produced reliable and repeatable results. aSTRs showed fewer drop outs than the Y- and X-STRs., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2017
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38. Enabling N-to-C Ser/Thr Ligation for Convergent Protein Synthesis via Combining Chemical Ligation Approaches.
- Author
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Lee CL, Liu H, Wong CT, Chow HY, and Li X
- Subjects
- Amino Acid Sequence, Chemistry Techniques, Synthetic, Interleukin-17 chemical synthesis, Interleukin-17 chemistry, Oligopeptides chemical synthesis, Oligopeptides chemistry, Proteins chemistry, Carbon chemistry, Cysteine chemistry, Nitrogen chemistry, Proteins chemical synthesis, Serine chemistry
- Abstract
In this article, Ser/Thr ligation(on/off) has been realized to enable N-to-C successive peptide ligations using a salicylaldehyde semicarbazone (SAL(off)) group by in situ activation with pyruvic acid of the peptide SAL(off) ester into the peptide salicylaldehyde (SAL(on)) ester. In addition, a peptide with a C-terminal thioester and N-terminal Ser or Thr as the middle peptide segment can undergo one-pot Ser/Thr ligation and native chemical ligation in the N-to-C direction. The utility of this combined ligation strategy in the N-to-C direction has been showcased through the convergent assembly of a human cytokine protein sequence, GlcNAcylated interleukin-25.
- Published
- 2016
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39. Pak2 restrains endomitosis during megakaryopoiesis and alters cytoskeleton organization.
- Author
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Kosoff RE, Aslan JE, Kostyak JC, Dulaimi E, Chow HY, Prudnikova TY, Radu M, Kunapuli SP, McCarty OJ, and Chernoff J
- Subjects
- Animals, Blood Platelets pathology, Bone Marrow metabolism, Bone Marrow pathology, Cytoskeleton metabolism, Megakaryocytes pathology, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, SCID, Microscopy, Fluorescence, Polyploidy, Stem Cells metabolism, Stem Cells pathology, Thrombocytopenia pathology, Blood Platelets metabolism, Cytoskeleton pathology, Megakaryocytes metabolism, Mitosis genetics, PAX2 Transcription Factor physiology, Thrombocytopenia genetics, Thrombopoiesis physiology
- Abstract
Megakaryocyte maturation and polyploidization are critical for platelet production; abnormalities in these processes are associated with myeloproliferative disorders, including thrombocytopenia. Megakaryocyte maturation signals through cascades that involve p21-activated kinase (Pak) function; however, the specific role for Pak kinases in megakaryocyte biology remains elusive. Here, we identify Pak2 as an essential effector of megakaryocyte maturation, polyploidization, and proplatelet formation. Genetic deletion of Pak2 in murine bone marrow is associated with macrothrombocytopenia, altered megakaryocyte ultrastructure, increased bone marrow megakaryocyte precursors, and an elevation of mature CD41(+) megakaryocytes, as well as an increased number of polyploid cells. In Pak2(-/-) mice, platelet clearance rate was increased, as was production of newly synthesized, reticulated platelets. In vitro, Pak2(-/-) megakaryocytes demonstrate increased polyploidization associated with alterations in β1-tubulin expression and organization, decreased proplatelet extensions, and reduced phosphorylation of the endomitosis regulators LIM domain kinase 1, cofilin, and Aurora A/B/C. Together, these data establish a novel role for Pak2 as an important regulator of megakaryopoiesis, polyploidization, and cytoskeletal dynamics in developing megakaryocytes., (© 2015 by The American Society of Hematology.)
- Published
- 2015
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40. Group I Paks as therapeutic targets in NF2-deficient meningioma.
- Author
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Chow HY, Dong B, Duron SG, Campbell DA, Ong CC, Hoeflich KP, Chang LS, Welling DB, Yang ZJ, and Chernoff J
- Subjects
- Animals, Antineoplastic Agents pharmacology, Brain drug effects, Brain metabolism, Brain pathology, Cell Line, Tumor, Cell Proliferation drug effects, Cell Proliferation genetics, Doxycycline pharmacology, Gene Expression Regulation, Neoplastic, Humans, Immunoblotting, Meningioma genetics, Meningioma therapy, Mice, SCID, Neurofibromin 2 genetics, Pyridones pharmacology, Pyrimidines pharmacology, RNA Interference, RNAi Therapeutics, Reverse Transcriptase Polymerase Chain Reaction, Tumor Burden drug effects, Tumor Burden genetics, Xenograft Model Antitumor Assays methods, p21-Activated Kinases antagonists & inhibitors, p21-Activated Kinases genetics, Meningioma metabolism, Neurofibromin 2 deficiency, p21-Activated Kinases metabolism
- Abstract
Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterized by the development of multiple tumors in the central nervous system, most notably schwannomas and meningiomas. Mutational inactivation of NF2 is found in 40-60% of sporadic meningiomas, but the molecular mechanisms underlying malignant changes of meningioma cells remain unclear. Because group I p21-activated kinases (Paks) bind to and are inhibited by the NF2-encoded protein Merlin, we assessed the signaling and anti-tumor effects of three group-I specific Pak inhibitors - Frax597, 716 and 1036 - in NF2-/- meningiomas in vitro and in an orthotopic mouse model. We found that these Pak inhibitors suppressed the proliferation and motility of both benign (Ben-Men1) and malignant (KT21-MG1) meningiomas cells. In addition, we found a strong reduction in phosphorylation of Mek and S6, and decreased cyclin D1 expression in both cell lines after treatment with Pak inhibitors. Using intracranial xenografts of luciferase-expressing KT21-MG1 cells, we found that treated mice showed significant tumor suppression for all three Pak inhibitors. Similar effects were observed in Ben-Men1 cells. Tumors dissected from treated animals exhibited an increase in apoptosis without notable change in proliferation. Collectively, these results suggest that Pak inhibitors might be useful agents in treating NF2-deficient meningiomas.
- Published
- 2015
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41. Proteomics analysis of co-purifying cellular proteins associated with rAAV vectors.
- Author
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Dong B, Duan X, Chow HY, Chen L, Lu H, Wu W, Hauck B, Wright F, Kapranov P, and Xiao W
- Subjects
- Blotting, Western, Capsid Proteins isolation & purification, Chromatography, Liquid, Dependovirus genetics, Electrophoresis, Gel, Two-Dimensional, Genetic Therapy methods, Genetic Therapy standards, Genetic Vectors genetics, Humans, Mass Spectrometry, Proteome isolation & purification, Reproducibility of Results, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Capsid Proteins analysis, Dependovirus metabolism, Proteome analysis, Proteomics methods
- Abstract
Recombinant adeno-associated vectors (rAAV) are commonly purified by either chromatography or equilibrium CsCl gradient. Nevertheless, even after purification various cellular proteins often associate with rAAV vector capsids. Such co-purifying cellular proteins may raise concern about safety of gene therapy. Here we report identification and characterization of the co-purifying cellular protein in the vector preparations by using a combination of two proteomics approaches, GeLC-MS (gel electrophoresis liquid chromatography-mass spectrometry) and 2DE (two-dimensional gel electrophoresis). Most prominent bands revealed by Coomassie Blue staining were mostly similar to the AAV capsid proteins. Posttranslational modifications of capsid proteins were detected by the proteomics analysis. A total of 13 cellular proteins were identified in the rAAV vectors purified by two rounds of cesium chloride gradient centrifugation, including 9 by the GeLC-MS analysis and 4 by the 2DE analysis. Selected cellular proteins were verified by western blot. Furthermore, the cellular proteins could be consistently found associated with different AAV serotypes and carrying different transgenes. Yet, the proteins were not integral components of the viral capsis since a stringent washing procedure by column purification could remove them. These co-purified proteins in AAV vector preparations may have a role in various stages of the AAV life cycle.
- Published
- 2014
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42. Identification of a new class of FtsZ inhibitors by structure-based design and in vitro screening.
- Author
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Chan FY, Sun N, Neves MA, Lam PC, Chung WH, Wong LK, Chow HY, Ma DL, Chan PH, Leung YC, Chan TH, Abagyan R, and Wong KY
- Subjects
- Animals, Anti-Bacterial Agents chemistry, Binding Sites, Cattle, Drug Evaluation, Preclinical, Escherichia coli drug effects, GTP Phosphohydrolases chemistry, GTP Phosphohydrolases metabolism, Guanosine Triphosphate metabolism, Humans, Molecular Docking Simulation, Protein Conformation, Protein Multimerization drug effects, Protein Structure, Quaternary, Pyrimidines chemistry, Quinuclidines chemistry, Sequence Homology, Amino Acid, Staphylococcus aureus drug effects, Staphylococcus aureus enzymology, Structure-Activity Relationship, Tubulin chemistry, Anti-Bacterial Agents pharmacology, Drug Design, Enzyme Inhibitors chemistry, Enzyme Inhibitors pharmacology, GTP Phosphohydrolases antagonists & inhibitors
- Abstract
The Filamenting temperature-sensitive mutant Z (FtsZ), an essential GTPase in bacterial cell division, is highly conserved among Gram-positive and Gram-negative bacteria and thus considered an attractive target to treat antibiotic-resistant bacterial infections. In this study, a new class of FtsZ inhibitors bearing the pyrimidine-quinuclidine scaffold was identified from structure-based virtual screening of natural product libraries. Iterative rounds of in silico studies and biological evaluation established the preliminary structure-activity relationships of the new compounds. Potent FtsZ inhibitors with low micromolar IC₅₀ and antibacterial activity against S. aureus and E. coli were found. These findings support the use of virtual screening and structure-based design for the rational development of new antibacterial agents with innovative mechanisms of action.
- Published
- 2013
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- View/download PDF
43. Pak2 kinase restrains mast cell FcεRI receptor signaling through modulation of Rho protein guanine nucleotide exchange factor (GEF) activity.
- Author
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Kosoff R, Chow HY, Radu M, and Chernoff J
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- Animals, Base Sequence, Bone Marrow Cells metabolism, Calcium metabolism, Cell Adhesion, Cells, Cultured, DNA Primers, Mice, Polymerase Chain Reaction, p21-Activated Kinases, Guanine Nucleotide Exchange Factors metabolism, Mast Cells metabolism, Mice, Inbred C57BL metabolism, Receptors, IgE metabolism, Signal Transduction
- Abstract
p21-activated kinase-1 (Pak1) is a serine/threonine kinase that plays a key role in mediating antigen-stimulated extracellular calcium influx and degranulation in mast cells. Another isoform in this kinase family, Pak2, is expressed at very high levels in mast cells, but its function is unknown. Here we show that Pak2 loss in murine bone marrow-derived mast cells, unlike loss of Pak1, induces increased antigen-mediated adhesion, degranulation, and cytokine secretion without changes to extracellular calcium influx. This phenotype is associated with an increase in RhoA-GTPase signaling activity to downstream effectors, including myosin light chain and p38(MAPK), and is reversed upon treatment with a Rho-specific inhibitor. Pak2, but not Pak1, negatively regulates RhoA via phosphorylation of the guanine nucleotide exchange factor GEF-H1 at an inhibitory site, leading to increased GEF-H1 microtubule binding and loss of RhoA stimulation. These data suggest that Pak2 plays a unique inhibitory role in mast cell degranulation by down-regulating RhoA via GEF-H1.
- Published
- 2013
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- View/download PDF
44. p21-Activated kinase 1 is required for efficient tumor formation and progression in a Ras-mediated skin cancer model.
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Chow HY, Jubb AM, Koch JN, Jaffer ZM, Stepanova D, Campbell DA, Duron SG, O'Farrell M, Cai KQ, Klein-Szanto AJ, Gutkind JS, Hoeflich KP, and Chernoff J
- Subjects
- Animals, Carcinoma, Squamous Cell genetics, Carcinoma, Squamous Cell pathology, Down-Regulation, Extracellular Signal-Regulated MAP Kinases metabolism, Gene Deletion, Genes, ras, Humans, Immunohistochemistry, Mice, Mice, Knockout, Mice, Transgenic, Neoplasm Grading, Neoplasm Staging, Oncogene Protein v-akt metabolism, Proto-Oncogene Proteins genetics, Proto-Oncogene Proteins p21(ras), Signal Transduction, Skin Neoplasms genetics, Skin Neoplasms pathology, p21-Activated Kinases antagonists & inhibitors, p21-Activated Kinases deficiency, p21-Activated Kinases genetics, ras Proteins genetics, Carcinoma, Squamous Cell enzymology, Proto-Oncogene Proteins metabolism, Pyridones pharmacology, Pyrimidines pharmacology, Skin Neoplasms enzymology, p21-Activated Kinases biosynthesis, ras Proteins metabolism
- Abstract
The RAS genes are the most commonly mutated oncogenes in human cancer and present a particular therapeutic dilemma, as direct targeting of Ras proteins by small molecules has proved difficult. Signaling pathways downstream of Ras, in particular Raf/Mek/Erk and PI3K/Akt/mTOR, are dominated by lipid and protein kinases that provide attractive alternate targets in Ras-driven tumors. As p21-activated kinase 1 (Pak1) has been shown to regulate both these signaling pathways and is itself upregulated in many human cancers, we assessed the role of Pak1 in Ras-driven skin cancer. In human squamous cell carcinoma (SCC), we found a strong positive correlation between advanced stage and grade and PAK1 expression. Using a mouse model of Kras-driven SCC, we showed that deletion of the mouse Pak1 gene led to markedly decreased tumorigenesis and progression, accompanied by near total loss of Erk and Akt activity. Treatment of Kras(G12D) mice with either of two distinct small molecule Pak inhibitors (PF3758309 and FRAX597) caused tumor regression and loss of Erk and Akt activity. Tumor regression was also seen in mice treated with a specific Mek inhibitor, but not with an Akt inhibitor. These findings establish Pak1 as a new target in KRAS-driven tumors and suggest a mechanism of action through the Erk, but not the Akt, signaling pathway., (©2012 AACR.)
- Published
- 2012
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45. Recombinant human arginase inhibits the in vitro and in vivo proliferation of human melanoma by inducing cell cycle arrest and apoptosis.
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Lam TL, Wong GK, Chow HY, Chong HC, Chow TL, Kwok SY, Cheng PN, Wheatley DN, Lo WH, and Leung YC
- Subjects
- Animals, Cell Proliferation drug effects, Clinical Trials as Topic, Humans, Melanoma physiopathology, Mice, Mice, Inbred BALB C, Mice, Nude, Skin Neoplasms drug therapy, Skin Neoplasms pathology, Skin Neoplasms physiopathology, Tumor Cells, Cultured, Xenograft Model Antitumor Assays, raf Kinases antagonists & inhibitors, Apoptosis drug effects, Arginase genetics, Arginase pharmacology, Arginase therapeutic use, Cell Cycle drug effects, Melanoma drug therapy, Melanoma pathology, Recombinant Proteins genetics, Recombinant Proteins pharmacology, Recombinant Proteins therapeutic use
- Abstract
Melanoma has been shown to require arginine for growth, thus providing a potential Achilles' heel for therapeutic exploitation. Our investigations show that arginine depletion, using a recombinant form of human arginase I (rhArg), efficiently inhibits the growth of mammalian melanoma cell lines in vitro. These cell lines are consistently deficient in ornithine transcarbamylase (OTC) expression, correlating with their sensitivity to rhArg. Cell cycle distribution of A375 human melanoma cells treated with rhArg showed a remarkable dual-phase cell cycle arrest in S and G₂/M phases, in contrast to the G₂/M single-phase arrest observed with arginine deiminase (ADI), another arginine-degrading enzyme. rhArg and ADI both induced substantial apoptosis in A375 cells, accompanied by global modulation of cell cycle- and apoptosis-related transcription. Moreover, PEGylated rhArg dramatically inhibited the growth of A375 and B16 melanoma xenografts in vivo. Our results establish for the first time that (PEGylated) rhArg is a promising candidate for effective melanoma treatment, with fewer safety issues than ADI. Insight into the mechanism behind the antiproliferative activity of rhArg could inform us in designing combination therapies for future clinical trials., (© 2010 John Wiley & Sons A/S.)
- Published
- 2011
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46. p21-Activated kinases are required for transformation in a cell-based model of neurofibromatosis type 2.
- Author
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Chow HY, Stepanova D, Koch J, and Chernoff J
- Subjects
- Animals, Cell Adhesion, Cell Movement, Cell Shape, Gene Knockdown Techniques, Humans, Immunoblotting, Mice, Mice, Inbred BALB C, Mice, Nude, NIH 3T3 Cells, Neoplasms, Experimental genetics, Neoplasms, Experimental pathology, Neurofibromatosis 2 genetics, Neurofibromatosis 2 pathology, Neurofibromin 2 genetics, Neurofibromin 2 metabolism, Signal Transduction, Transplantation, Heterologous, p21-Activated Kinases genetics, Cell Transformation, Neoplastic, Neoplasms, Experimental metabolism, Neurofibromatosis 2 metabolism, p21-Activated Kinases metabolism
- Abstract
Background: NF2 is an autosomal dominant disease characterized by development of bilateral vestibular schwannomas and other benign tumors in central nervous system. Loss of the NF2 gene product, Merlin, leads to aberrant Schwann cell proliferation, motility, and survival, but the mechanisms by which this tumor suppressor functions remain unclear. One well-defined target of Merlin is the group I family of p21-activated kinases, which are allosterically inhibited by Merlin and which, when activated, stimulate cell cycle progression, motility, and increased survival. Here, we examine the effect of Pak inhibition on cells with diminished Merlin function., Methodology/principal Findings: Using a specific peptide inhibitor of group I Paks, we show that loss of Pak activity restores normal cell movement in cells lacking Merlin function. In addition, xenografts of such cells form fewer and smaller tumors than do cells without Pak inhibition. However, in tumors, loss of Pak activity does not reduce Erk or Akt activity, two signaling proteins that are thought to mediate Pak function in growth factor pathways., Conclusions/significance: These results suggest that Pak functions in novel signaling pathways in NF2, and may serve as a useful therapeutic target in this disease.
- Published
- 2010
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- View/download PDF
47. Development of a low-cost polymerase chain reaction-based method for studying differentially expressed genes in developing rice leaves.
- Author
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Fung YW, Chow HY, Law TW, Dong B, and Kwan HS
- Subjects
- Blotting, Northern, Gene Expression Regulation, Developmental, Gene Expression Regulation, Plant, Genes, Plant, Plant Leaves growth & development, RNA, Plant genetics, RNA, Plant metabolism, Reproducibility of Results, Gene Expression Profiling economics, Gene Expression Profiling methods, Oryza genetics, Oryza growth & development, Plant Leaves genetics, Polymerase Chain Reaction economics, Polymerase Chain Reaction methods
- Abstract
Gene expression studies are important for revealing gene functions putatively involved in biological processes. We were interested in identifying differentially expressed genes during leaf development in rice. We combined the RNA arbitrarily primed-polymerase chain reaction (RAP-PCR) and dot blot hybridization methods to screen a rice leaf primordium cDNA library. Three developmental stages during vegetative growth were examined. The cDNA clones showing different hybridization patterns were further analyzed and verified. Here we demonstrate that the combination of RAP-PCR and dot blot hybridization could provide an efficient and relatively low-cost cDNA library screening approach to discover genes not previously known to be associated with leaf development in rice. We believe that the findings described here will help to elucidate the molecular mechanism(s) underlying the developmental processes of rice leaf.
- Published
- 2009
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48. Identification of alpha-actinin 4 and 67 kDa laminin receptor as stage-specific markers in esophageal cancer via proteomic approaches.
- Author
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Fu L, Qin YR, Xie D, Chow HY, Ngai SM, Kwong DL, Li Y, and Guan XY
- Subjects
- Female, Humans, Male, Middle Aged, Neoplasm Metastasis, Prognosis, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Actinin analysis, Biomarkers, Tumor analysis, Carcinoma, Squamous Cell chemistry, Carcinoma, Squamous Cell pathology, Esophageal Neoplasms chemistry, Esophageal Neoplasms pathology, Microfilament Proteins analysis, Neoplasm Staging methods, Protein Array Analysis, Proteomics, Receptors, Laminin analysis
- Abstract
Background: Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies in the world with a very poor prognosis. The majority of ESCC patients present with advanced metastatic disease upon diagnosis. Therefore, it is important to understand the molecular mechanism in the tumor invasion process and to find new biomarkers for early diagnosis and prognostic evaluation., Methods: Differentially expressed proteins among different stages of primary ESCCs and their matched surrounding normal tissues were compared by proteomics-based technology. The correlations between interesting proteins and clinical features of ESCC were further investigated by using ESCC tissue microarray (TMA) by immunohistochemical staining., Results: Compared with normal tissues, a total of 18 differentially expressed proteins were identified in ESCC in this study. Among them, expression levels of alpha-actinin 4 (ACTN4) and 67 kDa laminin receptor (67LR) were progressively increased from stage I to III. Clinicopathological correlation using TMA revealed that overexpression of ACTN4 was significantly associated with advanced tumor stage (P = .026) and lymph node metastasis (P = .049), whereas overexpression of 67LR was significantly correlated with advanced tumor stage (P = .019) but not lymph node metastasis., Conclusions: These findings suggested that overexpression of ACTN4 and 67 LR is associated with ESCC progression and that these biomarkers may potentially be useful to prognostic evaluation, molecular biological classification, and therapeutic targeting.
- Published
- 2007
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49. Acute calcific tendinitis of the hip: case report with magnetic resonance imaging findings.
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Chow HY, Recht MP, Schils J, and Calabrese LH
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- Acute Disease, Calcinosis diagnostic imaging, Female, Hip Joint diagnostic imaging, Hip Joint pathology, Humans, Magnetic Resonance Imaging, Middle Aged, Pelvis diagnostic imaging, Psoas Muscles diagnostic imaging, Radiography, Tendinopathy diagnostic imaging, Calcinosis diagnosis, Tendinopathy diagnosis
- Abstract
The clinical presentation of acute calcific tendinitis can be quite dramatic. This report describes a patient with this entity who had calcification in an unusual area, accompanied by abnormalities seen on radiography and magnetic resonance imaging. Clinical aspects of acute calcific tendinitis are also reviewed. With recognition of this entity, treatment can be initiated promptly, with dramatic resolution.
- Published
- 1997
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50. Cardiovascular effects of Gardenia florida L. (Gardeniae Fructus) extract.
- Author
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Chow HY, Wang JC, and Cheng KK
- Subjects
- Animals, Blood Pressure drug effects, Cardiac Output drug effects, In Vitro Techniques, Lethal Dose 50, Male, Medicine, Chinese Traditional, Mice, Myocardial Contraction drug effects, Plant Extracts toxicity, Rats, Cardiovascular System drug effects, Plant Extracts pharmacology, Plants, Medicinal
- Abstract
Intravenous injection of Gardeniae Fructus extract in rats significantly lowered the systemic arterial pressure which was related to a decreased cardiac output with decreased stroke volume. Gareniae Fructus extract decreased the myocardial contractility of perfused isolated rat heart. Electrocardiogram revealed evidence of myocardial damage and atrioventricular block after a large dose of the extract.
- Published
- 1976
- Full Text
- View/download PDF
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