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To J, Zhang X, Tam JP. Design of Potent and Salt-Insensitive Antimicrobial Branched Peptides. Polymers (Basel) 2023; 15:3594. [PMID: 37688220 PMCID: PMC10489980 DOI: 10.3390/polym15173594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/24/2023] [Accepted: 08/26/2023] [Indexed: 09/10/2023] Open
Abstract
Dendrimeric and branched peptides are polypeptides formed by diverse types of scaffolds to give them different forms. Previously, we reported a cascade-type, Lys-scaffolded antimicrobial peptide dendrimer D4R tethered with four RLYR tetrapeptides. Antimicrobial D4R is broad-spectrum, salt insensitive, and as potent as the natural-occurring tachyplesins, displaying minimum inhibitory concentrations (MIC) < 1 μM. However, the relationships between scaffolds and antimicrobial potency remain undefined. Here, we report the design of four novel types of peptide antimicrobials whose scaffolded backbones are lysine (Lys), iso-Lys, ornithine (Orn), or iso-Orn tethered with RLYR on their α- or sidechain-amines to give ε-, δ-, and their α-branched peptides. When assayed against ten microorganisms, the Lys-scaffolded α- and ε-branched peptides are broadly active, salt insensitive, and as potent as D4R and tachyplesins, whereas the corresponding Orn-scaffolded α- and δ-branched peptides are salt sensitive and much less potent, displaying MICs ranging from 1 to >500 μM. Structure-activity relationship studies suggested that Lys-scaffolds, but not Orn-scaffolds, can support a reverse turn to organize RLYR tetrapeptides as parallel β-strands to form an amphipathic structure with Leu-Tyr as a hydrophobic core. Together, these results provide a structural approach for designing potent and salt-insensitive dendrimeric or branched peptide antimicrobials.
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Affiliation(s)
| | | | - James P. Tam
- Synzymes and Natural Products Center (SYNC), School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
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2
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Derish I, Zwaig J, Khan K, Derish D, To J, Young P, Cecere R. A preliminary study of patient-specific differences in induced pluripotent stem cell-derived cardiomyocytes following hypoxia-induced injury. Cardiovasc Res 2022. [DOI: 10.1093/cvr/cvac066.072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): Courtois Cardiovascular Signature Program
The increasing rate of cardiovascular disease (CVD) contributes to a worsening morbidity in the general population and a socioeconomic burden on the healthcare system. Newly approved therapies present unforeseen side effects and occasionally entail adverse cardiovascular responses in patients - this issue significantly stalls efficacious pharmacological development. Indeed, modern cardiovascular treatments do not account for the variability of individual patient reactions, due to a lack of a representative in vitro cardiac model. While the use of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has gained traction as a superior model for drug screening when compared to cardiac biopsies and immortalized cell lines, cardiovascular patient-specific differences remain poorly understood and understudied.
We hypothesized that 1) cardiomyopathic patient-derived iPSC-CMs have differing baselines of beating rate, contractility, viability, metabolic activity and protein expression, when compared to healthy controls, and that 2) cell lines have patient-specific responses to hypoxia-induced injury. As such, the purpose of this preliminary study was two-fold: 1) to perform a characterization of patient iPSC-CM function, and 2) to study patient-specific cellular responses to hypoxia.
First, we generated iPSC-CMs from the peripheral blood of donors (n=6 patients with cardiomyopathies, n=2 healthy donors). We then confirmed the expression of prominent cardiac markers connexin 43 (CXN43), sarcoendoplasmic reticulum Ca2+ ATPase (SERCA2a), GATA4 and cardiac Troponin T, as well as a lack of pluripotency markers Octamer-binding transcription factor 4 (OCT4), Nanog, Stage-specific embryonic antigen-4 (SSEA-4) and TRA-1-60 in the iPSC-CM lines, via immunocytochemistry. Preliminary assessment of iPSC-CMs (days 1-30 post-differentiation) revealed significant baseline differences in beating rate (p<0.01) and contractility amplitude (p<0.01) between iPSC-CMs derived from cardiomyopathic patients and healthy donors.
We then subjected iPSC-CM lines to hypoxic conditions (24 hours), to mimic ischaemic injury. Diseased patient-derived lines had significantly decreased viability and metabolic activity when compared to the controls, under normoxic (p<0.01) and hypoxic conditions (p<0.001). Immunoblotting revealed differential expression of cardiac markers and factors implicated in cardiac function, cardioprotection and pathology. Taken together, these results suggest that the detected differences at the cellular level after hypoxia-induced injury might be translatable to the inter-individual variability currently observed in the CVD patient population. The data gathered will prove to be instrumental in future studies of iPSC-CM responses to treatment. With this preliminary study, we hope to shift the focus towards these patient-specific differences at the cellular level, in the search for tailored therapies and a higher standard of care for CVD patients.
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Affiliation(s)
- I Derish
- McGill University Health Centre , Montreal , Canada
| | - J Zwaig
- McGill University Health Centre , Montreal , Canada
| | - K Khan
- McGill University Health Centre , Montreal , Canada
| | - D Derish
- McGill University Health Centre , Montreal , Canada
| | - J To
- McGill University Health Centre , Montreal , Canada
| | - P Young
- McGill University Health Centre , Montreal , Canada
| | - R Cecere
- McGill University Health Centre , Montreal , Canada
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Liew HT, To J, Zhang X, Hemu X, Chan NY, Serra A, Sze SK, Liu CF, Tam JP. The legumain McPAL1 from Momordica cochinchinensis is a highly stable Asx-specific splicing enzyme. J Biol Chem 2021; 297:101325. [PMID: 34710371 PMCID: PMC8600085 DOI: 10.1016/j.jbc.2021.101325] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/09/2021] [Accepted: 10/11/2021] [Indexed: 11/29/2022] Open
Abstract
Legumains, also known as asparaginyl endopeptidases (AEPs), cleave peptide bonds after Asn/Asp (Asx) residues. In plants, certain legumains also have ligase activity that catalyzes biosynthesis of Asx-containing cyclic peptides. An example is the biosynthesis of MCoTI-I/II, a squash family-derived cyclic trypsin inhibitor, which involves splicing to remove the N-terminal prodomain and then N-to-C-terminal cyclization of the mature domain. To identify plant legumains responsible for the maturation of these cyclic peptides, we have isolated and characterized a legumain involved in splicing, McPAL1, from Momordica cochinchinensis (Cucurbitaceae) seeds. Functional studies show that recombinantly expressed McPAL1 displays a pH-dependent, trimodal enzymatic profile. At pH 4 to 6, McPAL1 selectively catalyzed Asp-ligation and Asn-cleavage, but at pH 6.5 to 8, Asn-ligation predominated. With peptide substrates containing N-terminal Asn and C-terminal Asp, such as is found in precursors of MCoTI-I/II, McPAL1 mediates proteolysis at the Asn site and then ligation at the Asp site at pH 5 to 6. Also, McPAL1 is an unusually stable legumain that is tolerant of heat and high pH. Together, our results support that McPAL1 is a splicing legumain at acidic pH that can mediate biosynthesis of MCoTI-I/II. We purport that the high thermal and pH stability of McPAL1 could have applications for protein engineering.
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Affiliation(s)
- Heng Tai Liew
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Xiaohong Zhang
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Xinya Hemu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Ning-Yu Chan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Aida Serra
- IMDEA Food Research Institute, +Pec Proteomics, Campus of International Excellence UAM+CSIC, Old Cantoblanco Hospital, Cantoblanco, Madrid, Spain; Proteored - Instituto de Salud Carlos III (ISCIII), Campus UAM, Cantoblanco, Madrid, Spain
| | - Siu Kwan Sze
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Chuan-Fa Liu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - James P Tam
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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4
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Xia Y, To J, Chan N, Hu S, Liew HT, Balamkundu S, Zhang X, Lescar J, Bhattacharjya S, Tam JP, Liu C. N
γ
‐Hydroxyasparagine: A Multifunctional Unnatural Amino Acid That is a Good P1 Substrate of Asparaginyl Peptide Ligases. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yiyin Xia
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Janet To
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Ning‐Yu Chan
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Side Hu
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Heng Tai Liew
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Seetharamsing Balamkundu
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
- Singapore-MIT Alliance for Research and Technology Singapore 138602 Singapore
| | - Xiaohong Zhang
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Julien Lescar
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Surajit Bhattacharjya
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - James P. Tam
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
| | - Chuan‐Fa Liu
- School of Biological Sciences Nanyang Technological University 60 Nanyang Drive Singapore 637551 Singapore
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Xia Y, To J, Chan NY, Hu S, Liew HT, Balamkundu S, Zhang X, Lescar J, Bhattacharjya S, Tam JP, Liu CF. N γ -Hydroxyasparagine: A Multifunctional Unnatural Amino Acid That is a Good P1 Substrate of Asparaginyl Peptide Ligases. Angew Chem Int Ed Engl 2021; 60:22207-22211. [PMID: 34396662 DOI: 10.1002/anie.202108125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Indexed: 11/10/2022]
Abstract
Peptidyl asparaginyl ligases (PALs) are powerful tools for peptide macrocyclization. Herein, we report that a derivative of Asn, namely Nγ -hydroxyasparagine or Asn(OH), is an unnatural P1 substrate of PALs. By Asn(OH)-mediated cyclization, we prepared cyclic peptides as new matrix metalloproteinase 2 (MMP2) inhibitors displaying the hydroxamic acid moiety of Asn(OH) as the key pharmacophore. The most potent cyclic peptide (Ki =2.8±0.5 nM) was built on the hyperstable tetracyclic scaffold of rhesus theta defensin-1. The Asn(OH) residue in the cyclized peptides can also be readily oxidized to Asp. By this approach, we synthesized several bioactive Asp-containing cyclic peptides (MCoTI-II, kB2, SFTI, and integrin-targeting RGD peptides) that are otherwise difficult targets for PAL-catalyzed cyclization owing to unfavorable kinetics of the P1-Asp substrates. This study demonstrates that substrate engineering is a useful strategy to expand the application of PAL ligation in the synthesis of therapeutic cyclic peptides.
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Affiliation(s)
- Yiyin Xia
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Ning-Yu Chan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Side Hu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Heng Tai Liew
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Seetharamsing Balamkundu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.,Singapore-MIT Alliance for Research and Technology, Singapore, 138602, Singapore
| | - Xiaohong Zhang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - James P Tam
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Chuan-Fa Liu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
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Zhang D, Wang Z, Hu S, Balamkundu S, To J, Zhang X, Lescar J, Tam JP, Liu CF. pH-Controlled Protein Orthogonal Ligation Using Asparaginyl Peptide Ligases. J Am Chem Soc 2021; 143:8704-8712. [PMID: 34096285 DOI: 10.1021/jacs.1c02638] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Peptide asparaginyl ligases (PALs) catalyze transpeptidation at the Asn residue of a short Asn-Xaa1-Xaa2 tripeptide motif. Due to their high catalytic activity toward the P1-Asn substrates at around neutral pH, PALs have been used extensively for peptide ligation at asparaginyl junctions. PALs also bind to aspartyl substrates, but only when the γCOOH of P1-Asp remains in its neutral, protonated form, which usually requires an acidic pH. However, this limits the availability of the amine nucleophile and, consequently, the ligation efficiency at aspartyl junctions. Because of this perceived inefficiency, the use of PALs for Asp-specific ligation remains largely unexplored. We found that PAL enzymes, such as VyPAL2, display appreciable catalytic activities toward P1-Asp substrates at pH 4-5, which are at least 2 orders of magnitude higher than that of sortase A, making them practically useful for both intra- and intermolecular ligations. This also allows sequential ligations, first at Asp and then at Asn junctions, because the newly formed aspartyl peptide bond is resistant to the ligase at the pH used for asparaginyl ligation in the second step. Using this pH-controlled orthogonal ligation method, we dually labeled truncated sfGFP with a cancer-targeting peptide and a doxorubicin derivative at the respective N- and C-terminal ends in the N-to-C direction. In addition, a fluorescein tag and doxorubicin derivative were tagged to an EGFR-targeting affibody in the C-to-N direction. This study shows that the pH-dependent catalytic activity of PAL enzymes can be exploited to prepare multifunction protein biologics for pharmacological applications.
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Affiliation(s)
- Dingpeng Zhang
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Zhen Wang
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Side Hu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | | | - Janet To
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Xiaohong Zhang
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - James P Tam
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
| | - Chuan-Fa Liu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551
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To J, Torres J. Trimerization of the N-Terminal Tail of Zika Virus NS4A Protein: A Potential In Vitro Antiviral Screening Assay. Membranes (Basel) 2021; 11:membranes11050335. [PMID: 33946585 PMCID: PMC8147241 DOI: 10.3390/membranes11050335] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/25/2021] [Accepted: 04/28/2021] [Indexed: 12/26/2022]
Abstract
The nonstructural (NS) protein NS4A in flaviviruses is a membrane protein that is critical for virulence, and, among other roles, it participates in membrane morphogenesis. In dengue virus (DENV), the NS4A hydrophilic N–terminal tail, together with the first transmembrane domain, is involved in both homo-oligomerization and hetero–oligomerization with NS4B. In both DENV and Zika virus (ZIKV), this N-terminal tail (residues 1–48) forms a random coil in solution but becomes mostly α-helical upon interaction with detergents or lipid membranes. Herein, we show that a peptide from ZIKV NS4A that spans residues 4–58, which includes most of the N–terminal tail and a third of its first transmembrane domain, forms homotrimers in the absence of detergents or liposomes. After interaction with the latter, α–helical content increases, consistent with binding. The oligomeric size of NS4A is not known, as it has only been reported in SDS gels. Therefore, we propose that full-length NS4A forms homotrimers mediated by this region, and that disruption of the oligomerization of peptide ZIKV NS4A 4–58 in solution can potentially constitute the basis for an in vitro assay to discover antivirals.
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Wang Z, Zhang D, Hemu X, Hu S, To J, Zhang X, Lescar J, Tam JP, Liu CF. Engineering protein theranostics using bio-orthogonal asparaginyl peptide ligases. Theranostics 2021; 11:5863-5875. [PMID: 33897886 PMCID: PMC8058723 DOI: 10.7150/thno.53615] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 02/18/2021] [Indexed: 12/19/2022] Open
Abstract
Background: Protein theranostics integrate both diagnostic and treatment functions on a single disease-targeting protein. However, the preparation of these multimodal agents remains a major challenge. Ideally, conventional recombinant proteins should be used as starting materials for modification with the desired detection and therapeutic functionalities, but simple chemical strategies that allow the introduction of two different modifications into a protein in a site-specific manner are not currently available. We recently discovered two highly efficient peptide ligases, namely butelase-1 and VyPAL2. Although both ligate at asparaginyl peptide bonds, these two enzymes are bio-orthogonal with distinguishable substrate specificities, which can be exploited to introduce distinct modifications onto a protein. Methods: We quantified substrate specificity differences between butelase-1 and VyPAL2, which provide orthogonality for a tandem ligation method for protein dual modifications. Recombinant proteins or synthetic peptides engineered with the preferred recognition motifs of butelase-1 and VyPAL2 at their respective C- and N-terminal ends could be modified consecutively by the action of the two ligases. Results: Using this method, we modified an EGFR-targeting affibody with a fluorescein tag and a mitochondrion-lytic peptide at its respective N- and C-terminal ends. The dual-labeled protein was found to be a selective bioimaging and cytotoxic agent for EGFR-positive A431 cancer cells. In addition, the method was used to prepare a cyclic form of the affibody conjugated with doxorubicin. Both modified affibodies showed increased cytotoxicity to A431 cells by 10- and 100-fold compared to unconjugated doxorubicin and the free peptide, respectively. Conclusion: Bio-orthogonal tandem ligation using two asparaginyl peptide ligases with differential substrate specificities is a straightforward approach for the preparation of multifunctional protein biologics as potential theranostics.
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Hemu X, Zhang X, Nguyen GKT, To J, Serra A, Loo S, Sze SK, Liu CF, Tam JP. Characterization and application of natural and recombinant butelase-1 to improve industrial enzymes by end-to-end circularization. RSC Adv 2021; 11:23105-23112. [PMID: 35480425 PMCID: PMC9034278 DOI: 10.1039/d1ra03763c] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/23/2021] [Indexed: 01/14/2023] Open
Abstract
Butelase-1, an asparaginyl endopeptidase or legumain, is the prototypical and fastest known Asn/Asp-specific peptide ligase that could be used for improving other enzymes by catalyzing simple and efficient end-to-end circularization.
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Affiliation(s)
- Xinya Hemu
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - Xiaohong Zhang
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - Giang K. T. Nguyen
- WIL@NUS Corporate Lab
- MD6 Centre for Translational Medicine
- Wilmar International Limited
- National University of Singapore
- Singapore
| | - Janet To
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - Aida Serra
- IMDEA Food Research Institute
- +Pec Proteomics
- Campus of International Excellence UAM+CSIC
- Old Cantoblanco Hospital
- Madrid 28049
| | - Shining Loo
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - Siu Kwan Sze
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - Chuan-Fa Liu
- School of Biological Sciences
- Nanyang Technological University
- Singapore
| | - James P. Tam
- School of Biological Sciences
- Nanyang Technological University
- Singapore
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Hemu X, To J, Zhang X, Tam JP. Correction to Immobilized Peptide Asparaginyl Ligases Enhance Stability and Facilitate Macrocyclization and Site-Specific Ligation. J Org Chem 2020; 85:4581. [DOI: 10.1021/acs.joc.0c00321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Hemu X, To J, Zhang X, Tam JP. Immobilized Peptide Asparaginyl Ligases Enhance Stability and Facilitate Macrocyclization and Site-Specific Ligation. J Org Chem 2019; 85:1504-1512. [DOI: 10.1021/acs.joc.9b02524] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xinya Hemu
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - Xiaohong Zhang
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - James P. Tam
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
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12
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Dutta B, Huang J, To J, Tam JP. LIR Motif-Containing Hyperdisulfide β-Ginkgotide is Cytoprotective, Adaptogenic, and Scaffold-Ready. Molecules 2019; 24:E2417. [PMID: 31262066 PMCID: PMC6651024 DOI: 10.3390/molecules24132417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/25/2019] [Accepted: 06/28/2019] [Indexed: 12/24/2022] Open
Abstract
Grafting a bioactive peptide onto a disulfide-rich scaffold is a promising approach to improve its structure and metabolic stability. The ginkgo plant-derived β-ginkgotide β-gB1 is a highly unusual molecule: Small, hyperdisulfide, and found only in selected ancient plants. It also contains a conserved 16-amino-acid core with three interlocking disulfides, as well as a six-amino-acid inter-cysteine loop 2 suitable for grafting peptide epitopes. However, very little is known about this recently-discovered family of molecules. Here, we report the biophysical and functional characterizations of the β-ginkgotide β-gB1 from G. biloba. A circular dichroism spectroscopy analysis at 90 °C and proteolytic treatments of β-gB1 supported that it is hyperstable. Data mining revealed that the β-gB1 loop 2 contains the canonical LC3 interacting region (LIR) motif crucial for selective autophagy. Cell-based assays and pull-down experiments showed that β-gB1 is an adaptogen, able to maintain cellular homeostasis through induced autophagosomes formation and to protect cells by targeting intracellular proteins from stress-mediated damage against hypoxia and the hypoxia-reoxygenation of induced cell death. This is the first report of an LIR-containing peptide natural product. Together, our results suggest that the plant-derived β-ginkgotide is cytoprotective, capable of targeting intracellular proteins, and holds promise as a hyperdisulfide scaffold for engineering peptidyl therapeutics with enhanced structural and metabolic stability.
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Affiliation(s)
- Bamaprasad Dutta
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jiayi Huang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - James P Tam
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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Abstract
Influenza is a highly contagious virus that causes seasonal epidemics and unpredictable pandemics. Four influenza virus types have been identified to date: A, B, C and D, with only A–C known to infect humans. Influenza A and B viruses are responsible for seasonal influenza epidemics in humans and are responsible for up to a billion flu infections annually. The M2 protein is present in all influenza types and belongs to the class of viroporins, i.e., small proteins that form ion channels that increase membrane permeability in virus-infected cells. In influenza A and B, AM2 and BM2 are predominantly proton channels, although they also show some permeability to monovalent cations. By contrast, M2 proteins in influenza C and D, CM2 and DM2, appear to be especially selective for chloride ions, with possibly some permeability to protons. These differences point to different biological roles for M2 in types A and B versus C and D, which is also reflected in their sequences. AM2 is by far the best characterized viroporin, where mechanistic details and rationale of its acid activation, proton selectivity, unidirectionality, and relative low conductance are beginning to be understood. The present review summarizes the biochemical and structural aspects of influenza viroporins and discusses the most relevant aspects of function, inhibition, and interaction with the host.
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Affiliation(s)
- Janet To
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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Phillips M, To J, Yamazaki T, Nagashima T, Torres J, Pervushin K. Binding of a small molecule water channel inhibitor to aquaporin Z examined by solid-state MAS NMR. J Biomol NMR 2018; 71:91-100. [PMID: 29916035 DOI: 10.1007/s10858-018-0195-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/01/2018] [Indexed: 06/08/2023]
Abstract
Aquaporins are integral membrane proteins that facilitate water flow across biological membranes. Their involvement in multiple physiological functions and disease states has prompted intense research to discover water channel activity modulators. However, inhibitors found so far are weak and/or lack specificity. For organic compounds, which lack of high electron-dense atoms, the identification of binding sites is even more difficult. Nuclear magnetic resonance spectroscopy (NMR) requires large amounts of the protein, and expression and purification of mammalian aquaporins in large quantities is a difficult task. However, since aquaporin Z (AqpZ) can be purified and expressed in good quantities and has a high similarity to human AQP1 (~ 40% identity), it can be used as a model for studying the structure and function of human aquaporins. In the present study, we have used solid-state MAS NMR to investigate the binding of a lead compound [1-(4-methylphenyl)1H-pyrrole-2,5-dione] to AqpZ, through mapping of chemical shift perturbations in the presence of the compound.
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Affiliation(s)
- Margaret Phillips
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Toshio Yamazaki
- RIKEN Centre for Life Science Technologies, Kanagawa, 230-0045, Japan
| | - Toshio Nagashima
- RIKEN Centre for Life Science Technologies, Kanagawa, 230-0045, Japan
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
| | - Konstantin Pervushin
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
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15
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Chau VM, Engeln JT, Axelrath S, Khatter SJ, Kwon R, Melton MA, Reinsvold MC, Staley VM, To J, Tanabe KJ, Wojcik R. Beyond the Chief Complaint: Our Patients' Worries. J Med Humanit 2017; 38:541-547. [PMID: 28975579 DOI: 10.1007/s10912-017-9479-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fourth-year medical students at the University of Colorado School of Medicine distributed cards to patients in the emergency department asking, "What Worries You Most?" The patients' responses provided insight about their most pressing concerns, often unrelated to their "chief complaints."
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Affiliation(s)
- V M Chau
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA.
| | - J T Engeln
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - S Axelrath
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - S J Khatter
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - R Kwon
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - M A Melton
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - M C Reinsvold
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - V M Staley
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - J To
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - K J Tanabe
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
| | - R Wojcik
- Gold Humanism Honor Society, Class of 2017, University of Colorado School of Medicine, Aurora, CO, USA
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16
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Bernardinelli E, Costa R, Scantamburlo G, To J, Morabito R, Nofziger C, Doerrier C, Krumschnabel G, Paulmichl M, Dossena S. Mis-targeting of the mitochondrial protein LIPT2 leads to apoptotic cell death. PLoS One 2017; 12:e0179591. [PMID: 28628643 PMCID: PMC5476274 DOI: 10.1371/journal.pone.0179591] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 06/01/2017] [Indexed: 11/27/2022] Open
Abstract
Lipoyl(Octanoyl) Transferase 2 (LIPT2) is a protein involved in the post-translational modification of key energy metabolism enzymes in humans. Defects of lipoic acid synthesis and transfer start to emerge as causes of fatal or severe early-onset disease. We show that the first 31 amino acids of the N-terminus of LIPT2 represent a mitochondrial targeting sequence and inhibition of the transit of LIPT2 to the mitochondrion results in apoptotic cell death associated with activation of the apoptotic volume decrease (AVD) current in normotonic conditions, as well as over-activation of the swelling-activated chloride current (IClswell), mitochondrial membrane potential collapse, caspase-3 cleavage and nuclear DNA fragmentation. The findings presented here may help elucidate the molecular mechanisms underlying derangements of lipoic acid biosynthesis.
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Affiliation(s)
- Emanuele Bernardinelli
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Roberta Costa
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Giada Scantamburlo
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Janet To
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Rossana Morabito
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
| | - Charity Nofziger
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | | | | | - Markus Paulmichl
- Center for Health and Bioresources, Austrian Institute of Technology, Vienna, Austria
| | - Silvia Dossena
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
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17
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To J, Surya W, Fung TS, Li Y, Verdià-Bàguena C, Queralt-Martin M, Aguilella VM, Liu DX, Torres J. Channel-Inactivating Mutations and Their Revertant Mutants in the Envelope Protein of Infectious Bronchitis Virus. J Virol 2017; 91:e02158-16. [PMID: 27974570 PMCID: PMC5309962 DOI: 10.1128/jvi.02158-16] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 12/06/2016] [Indexed: 02/06/2023] Open
Abstract
It has been shown previously in the severe acute respiratory syndrome coronavirus (SARS-CoV) that two point mutations, N15A and V25F, in the transmembrane domain (TMD) of the envelope (E) protein abolished channel activity and led to in vivo attenuation. Pathogenicity was recovered in mutants that also regained E protein channel activity. In particular, V25F was rapidly compensated by changes at multiple V25F-facing TMD residues located on a neighboring monomer, consistent with a recovery of oligomerization. Here, we show using infected cells that the same mutations, T16A and A26F, in the gamma-CoV infectious bronchitis virus (IBV) lead to, in principle, similar results. However, IBV E A26F did not abolish oligomer formation and was compensated by mutations at N- and C-terminal extramembrane domains (EMDs). The C-terminal EMD mutations clustered along an insertion sequence specific to gamma-CoVs. Nuclear magnetic resonance data are consistent with the presence of only one TMD in IBV E, suggesting that recovery of channel activity and fitness in these IBV E revertant mutants is through an allosteric interaction between EMDs and TMD. The present results are important for the development of IBV live attenuated vaccines when channel-inactivating mutations are introduced in the E protein.IMPORTANCE The ion channel activity of SARS-CoV E protein is a determinant of virulence, and abolishment of channel activity leads to viral attenuation. E deletion may be a strategy for generating live attenuated vaccines but can trigger undesirable compensatory mechanisms through modifications of other viral proteins to regain virulence. Therefore, a more suitable approach may be to introduce small but critical attenuating mutations. For this, the stability of attenuating mutations should be examined to understand the mechanisms of reversion. Here, we show that channel-inactivating mutations of the avian infectious bronchitis virus E protein introduced in a recombinant virus system are deficient in viral release and fitness and that revertant mutations also restored channel activity. Unexpectedly, most of the revertant mutations appeared at extramembrane domains, particularly along an insertion specific for gammacoronaviruses. Our structural data propose a single transmembrane domain in IBV E, suggesting an allosteric interaction between extramembrane and transmembrane domains.
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Affiliation(s)
- Janet To
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - To Sing Fung
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yan Li
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Carmina Verdià-Bàguena
- Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castelló, Spain
| | - Maria Queralt-Martin
- Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castelló, Spain
| | - Vicente M Aguilella
- Department of Physics, Laboratory of Molecular Biophysics. Universitat Jaume I, Castelló, Spain
| | - Ding Xiang Liu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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Hashi K, Deguchi K, Yamazaki T, Ohki S, Matsumoto S, Nishijima G, Goto A, Yamada K, Noguchi T, Sakai S, Takahashi M, Yanagisawa Y, Iguchi S, Maeda H, Tanaka R, Nemoto T, Suematsu H, To J, Torres J, Pervushin K, Shimizu T. Efficiency of High Magnetic Fields in Solid-state NMR. CHEM LETT 2016. [DOI: 10.1246/cl.151063] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Seiya Iguchi
- Center for Life Science Technologies, RIKEN
- Faculty of Science and Technology, Sophia University
| | | | | | | | | | - Janet To
- School of Biological Sciences, Nanyang Technological University
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University
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19
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Kearney B, To J, Southam K, Howie D, To B. Anaemia in elective orthopaedic surgery - Royal Adelaide Hospital, Australia. Intern Med J 2016; 46:96-101. [DOI: 10.1111/imj.12945] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/03/2015] [Accepted: 10/25/2015] [Indexed: 11/29/2022]
Affiliation(s)
- B. Kearney
- Site Clinical Director, Royal Adelaide Hospital; SA Pathology; Adelaide Australia
- Clinical Haematology Service; Royal Adelaide Hospital; Modbury Australia
| | - J. To
- Division of Aged Care; Rehabilitation and Palliative Care, Modbury Hospital; Adelaide Australia
| | - K. Southam
- Royal Adelaide Hospital; Orthopaedic Surgery and Trauma; Adelaide Australia
| | - D. Howie
- Department of Orthopaedic Surgery and Trauma; University of Adelaide, Royal Adelaide Hospital; Australia
| | - B. To
- Clinical Haematology Service; Royal Adelaide Hospital; Modbury Australia
- Clinical Section; Royal Adelaide Hospital Department of Haematology, SA Pathology; Adelaide South Australia Australia
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20
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Mehta S, Schwartz M, Fridman D, Levie M, To J, Chudnoff S. Office Hysteroscopy for the Removal of a Retained Intrauterine Device. J Minim Invasive Gynecol 2015; 22:S183. [DOI: 10.1016/j.jmig.2015.08.673] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Kuk N, To J, McBride C, Hong A, Ng E, Li N, Teo M, Zhang V, Velasco D, Ling L, Sun Y, Keem M. P14.02 Systematic review: does a positive human papillomavirus vaccination status increase the risk of unsafe sexual health practice in australian women? Br J Vener Dis 2015. [DOI: 10.1136/sextrans-2015-052270.514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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22
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To J, Yeo CY, Soon CH, Torres J. A generic high-throughput assay to detect aquaporin functional mutants: Potential application to discovery of aquaporin inhibitors. Biochim Biophys Acta Gen Subj 2015; 1850:1869-76. [PMID: 26028295 DOI: 10.1016/j.bbagen.2015.05.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 05/13/2015] [Accepted: 05/27/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND The discovery of stable, yet functional, protein mutants is a limiting factor in the development of biotechnological applications, structural studies or in drug discovery. Rapid detection of functional mutants is especially challenging for water channel aquaporins, as they do not have a directly measurable enzymatic or binding activity. Current methods available are time consuming and only applicable to specific aquaporins. METHODS Herein we describe an assay based on the protective effect of aquaporins on yeast S. cerevisiae in response to rapid freezing. RESULTS Yeast overexpressing a functional water-permeable aquaporin of choice are rescued after the challenge, while inactive or blocked aquaporins confer no protection and lead to cell death. The potential of this assay is shown by screening a small number of E. coli aquaporin Z (AQPZ) mutants. Additionally, a library of ~10,000 drug-like compounds was tested against human AQP1 (hAQP1). CONCLUSIONS Since rescue is only dependent on transmembrane water flux, the assay is applicable to water-permeable aquaporins of any origin. GENERAL SIGNIFICANCE Mapping of permissive mutations on the aquaporin structure can help delineate the minimal requirements for effective water transport. Alternatively, the assay can be potentially used to discover compounds that inhibit aquaporin water transport. When additionally screened for thermostability, functional aquaporin mutants can be useful in the development of biomimetic membranes for water purification, or to improve the likelihood of producing well-diffracting crystals, enabling rational design of much needed aquaporin inhibitors.
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Affiliation(s)
- Janet To
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Chiew Ying Yeo
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Cin Huang Soon
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
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23
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Bratman S, Newman A, To J, Wynne J, Neal J, Wakelee H, Shrager J, Loo B, Alizadeh A, Diehn M. Noninvasive and Ultrasensitive Quantitation of Circulating Tumor DNA by Hybrid Capture and Deep Sequencing. Int J Radiat Oncol Biol Phys 2013. [DOI: 10.1016/j.ijrobp.2013.06.237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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24
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Villavedra M, Lemke S, To J, Broady K, Wallach M, Raison RL. Carbohydrate epitopes are immunodominant at the surface of infectious Neoparamoeba spp. J Fish Dis 2007; 30:191-9. [PMID: 17394521 DOI: 10.1111/j.1365-2761.2007.00800.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Amoebic gill disease, the main disease of concern to the salmon industry in Tasmania, is caused by the amoeba, Neoparamoeba spp. Experimental infection can only be induced by exposure to wild-type (WT) parasites isolated from the gills of infected fish, as cultured amoebae are non-infective. To characterize the surface antigens of WT parasites, we produced monoclonal antibodies (mAbs) using subtractive immunization. Mice inoculated with non-infective parasites were treated with cyclophosphamide, to deplete reactive lymphocytes, and then immunized with different antigen preparations from infective parasites. When whole parasites were used for boosting, the percentage of WT unique mAbs was very high (86%) as was the percentage of mAbs specific for carbohydrate epitopes (89%). When deglycosylated membranes were used, the numbers of mAbs specific for non-carbohydrate epitopes did not increase, but the total number of WT unique mAbs was reduced (86-40%). Using an untreated membrane preparation, the total number of mAbs to surface molecules was very high, but all recognized carbohydrate epitopes. The total number of mAbs recognizing carbohydrate epitopes on the surface of the WT parasites was 97%, suggesting that the dominant epitopes on the surface molecules unique to WT parasites are carbohydrate in nature.
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Affiliation(s)
- M Villavedra
- Institute for Biotechnology of Infectious Diseases and Aquafin CRC, University of Technology, Sydney, Broadway, NSW, Australia.
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French S, Sokol A, To J, Catlow C, Phala N, Klatt G, van Steen E. Active sites for heterogeneous catalysis by functionalisation of internal and external surfaces. Catal Today 2004. [DOI: 10.1016/j.cattod.2004.06.129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ho DWY, Fan ST, To J, Woo YH, Zhang Z, Lau C, Wong J. Selective plasma filtration for treatment of fulminant hepatic failure induced by D-galactosamine in a pig model. Gut 2002; 50:869-76. [PMID: 12010892 PMCID: PMC1773226 DOI: 10.1136/gut.50.6.869] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/29/2001] [Indexed: 12/17/2022]
Abstract
BACKGROUND Plasma exchange may be useful for treating patients with fulminant hepatic failure but during the procedure growth factors that are important for hepatic regeneration are discarded. Addition of a selective plasma filter to the plasmapheresis circuit could eliminate protein bound toxic substances and retain growth factors for hepatic regeneration. This process is called selective plasma filtration. AIMS To determine if selective plasma filtration could be a useful treatment modality for fulminant hepatic failure. METHODS The system was tested in five groups of pigs with fulminant hepatic failure induced by galactosamine: group I, diseased control group (n=5); group II, sham control, (n=6); group III, plasma exchange (n=6); group IV, treatment with AC-1770 selective plasma filter (n=7); and group V, treatment with AC-1730 selective plasma filter which had a smaller pore size than AC-1770 (n=7). Fresh pig plasma was given to replace filtered plasma in pigs of groups III, IV, and V. Treatment was initiated 48 hours after administration of 0.75 g/kg galactosamine. The efficacy of selective plasma filtration was assessed by survival rate and improvement in haematological, biochemical, and immunohistological parameters. RESULTS Pigs treated with AC-1770 or AC-1730 selective plasma filters survived longer than the other groups (group I: 55 (10) hours; group II: 68 (7) hours; group III: 91 (10) hours; group IV: 269 (156) hours; group V: 950 (555) hours). One pig in group IV survived for 50 days; one pig in group V survived for 77 days and another pig in group V is still alive (>150 days). After treatment, plasma levels of aspartate aminotransferase, bilirubin, bile acid, ammonia, lactate dehydrogenase, and alpha-glutathione-S-transferase decreased. Substantial amounts of tumour necrosis factor alpha (TNF-alpha) and endotoxin were found in the filtrate. The selective plasma filtration groups retained significantly higher amounts of hepatocyte growth factor than plasma exchange alone. Similar TNF-alpha clearance was observed in the selective plasma filtration groups and the plasma exchange group. On day 4, significant improvement in liver function, as measured by the indocyanine green clearance test, was observed in groups IV and V but not in the other groups. A higher regeneration index of hepatocytes was also observed in the groups treated with AC-1770 and AC-1730 selective plasma filters. CONCLUSION Selective plasma filtration improved survival time and expedited liver regeneration in pigs with fulminant hepatic failure.
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Affiliation(s)
- D W Y Ho
- Centre for the Study of Liver Disease and Department of Surgery, University of Hong Kong, Hong Kong
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28
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To J, Issenman RM, Kamath MV. Evaluation of neurocardiac signals in pediatric patients with cyclic vomiting syndrome through power spectral analysis of heart rate variability. J Pediatr 1999; 135:363-6. [PMID: 10484804 DOI: 10.1016/s0022-3476(99)70135-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE To investigate autonomic regulation of neurocardiac signals in pediatric patients with cyclic vomiting syndrome (CVS). METHODS Fourteen patients with CVS, ages 3 to 16 years, were screened to eliminate any underlying cause for their symptoms, although 11 of the 14 patients had a history of migraine in the immediate family. Analysis of autonomic regulation was accomplished through power spectral analysis of the beat-to-beat heart rate variability signal. Data from affected patients were compared with data from 38 control subjects, ages 5 to 16 years, by a one-way analysis of variance. A measure of sympathovagal balance was obtained by computing a ratio of power in the low-frequency band (0. 02-0.15 Hz) to the power in the high-frequency band (0.15-0.4 Hz). RESULTS Pediatric patients with CVS have an elevated sympathetic modulation of the sinus node as represented by the low frequency/high frequency ratio (1.45 +/- 0.42 in patients vs 0.89 +/- 0.29 in healthy control subjects, P <.001). CONCLUSIONS The patients with CVS we studied have an autonomic imbalance with enhanced sympathetic and diminished parasympathetic vagal modulation of the heart.
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Affiliation(s)
- J To
- Division of Pediatrics, Children's Hospital, Hamilton Health Sciences Corporation and McMaster University, Hamilton, Ontario, Canada
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29
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Wang YN, Ng IO, To J, Fan ST. A modified method of auxiliary partial liver transplantation in the rat. Hepatogastroenterology 1999; 46:428-31. [PMID: 10228835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
BACKGROUND/AIMS In the animal model of auxiliary partial liver transplantation in the rat, the major problem is high outflow pressure since the direction of vascular outflow of the graft was perpendicular to that of the recipient inferior vena cava (IVC) and the anastomosis was far away from the right atrium. We aimed at developing an animal model that could prevent graft congestion. METHODOLOGY The graft contained the right lateral lobe and triangulated lobe of rat's liver. The modification of implantation included anatomizing an oblique cuff of IVC of donor graft into the recipient's IVC so that the size of anastomosis was large with an angle of 45 degrees and the resulting vascular outflow was no longer perpendicular to that of the recipient's IVC, and the creation of double grooves on the cuff body of the donor portal vein. Bile drainage was completed by inserting the bile duct (together with a stent) into the recipient's duodenum. RESULTS Congestion of grafts was not seen in 25 rats undergoing auxiliary partial liver transplantation using an oblique IVC graft. The 1-week and 2-week survival rates were 88% and 80%, respectively. In the group of rats (n = 10) operated on by using a straight IVC graft, graft congestion was seen and only 1 rat could survive over 1 day. CONCLUSIONS Modification of vascular outflow anastomosis prevented graft congestion and improved animal survival. The model may be useful for studying liver regeneration, transplantation immunology, and gene transfer.
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Affiliation(s)
- Y N Wang
- Department of Surgery, University of Hong Kong, Queen Mary Hospital, Hong Kong
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30
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Ohse H, Nomura A, Endoh T, Noguchi Y, Saotome M, Ninomiya H, Watanabe A, To J, Hashimoto K, Uchida Y. [Enkephalinase activity in the guinea pig model of asthma]. Arerugi 1993; 42:48-56. [PMID: 8384438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Enkephalinase exists in airway epithelial cells, smooth muscle, and submucosa near glands, and cleaves tachykinins to inactive metabolites, thereby reducing there effects. To study the role of enkephalinase in asthmatic response, we measured its activity in guinea pig model of asthma. When compared with the control values, the enkephalinase activity was reduced during in immediate asthmatic response (IAR) and late asthmatic response (LAR). Compared with the control values (100%), each value was 79.7%, 73.4% in the trachea and 74.3%, 55.7% in the lung respectively. Tracheal muscle preparation taken from the control, IAR, and LAR groups were made and mounted in oxygenated modified Krebs-Ringer solution. The response was monitored by isometric transducer. Concentration response curves to NKA with or without phosphoramidon were obtained. The contractile responses of the LAR groups were enhanced in potency and efficiency. Phosphoramidon potentiated the NKA induced contraction of control and the IAR groups but was less potent in enhancing the contractile response in the LAR group, showing less enkephalinase activity in the LAR. These results suggest that the enkephalinase plays an important role in LAR. In LAR, the enkephalinase activity may be inhibited and the responsiveness of the smooth muscle to some bronchoconstrictor, such as tachykinins, may be increased.
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Affiliation(s)
- H Ohse
- Division of Pulmonary Medicine, University of Tsukuba
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31
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Sanz-Gallén P, Nogué S, Munné P, To J. [Occupational lead poisoning treated with dimercaptosuccinic acid (DMSA) ( letter)]. Rev Clin Esp 1992; 191:58-9. [PMID: 1321469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Nogué S, Mas A, Parés A, Nadal P, Bertrán A, Millá J, Carrera M, To J, Pazos MR, Corbella J. Acute thallium poisoning: an evaluation of different forms of treatment. J Toxicol Clin Toxicol 1982; 19:1015-21. [PMID: 6308276 DOI: 10.3109/15563658208992536] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Hemodialysis, forced potassium diuresis, chelating agents per os, and Dithiocarb given intravenously during short periods of time were used for the treatment of acute thallium poisoning (ingestion of 750 mg of thallium sulfate), and the effectiveness of these different therapeutic procedures was analyzed. Chelating agents per os (Prussian blue, Dithiocarb, and Dithiozone) were ineffective in our patient, since fecal excretion of thallium was very low and unmodified by them. Forced potassium diuresis and hemodialysis were very useful therapeutic measures, especially in the first 12 days following ingestion. Dithiocarb perfusion seems to be the most effective method for enhancing urinary thallium excretion. This method might be most useful in the treatment of thallium poisoning if its deleterious effects could be eliminated.
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