1
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Ting DSJ, Li J, Verma CS, Goh ETL, Nubile M, Mastropasqua L, Said DG, Beuerman RW, Lakshminarayanan R, Mohammed I, Dua HS. Evaluation of Host Defense Peptide (CaD23)-Antibiotic Interaction and Mechanism of Action: Insights From Experimental and Molecular Dynamics Simulations Studies. Front Pharmacol 2021; 12:731499. [PMID: 34690770 PMCID: PMC8528955 DOI: 10.3389/fphar.2021.731499] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 09/27/2021] [Indexed: 11/13/2022] Open
Abstract
Background/Aim: Host defense peptides (HDPs) have the potential to provide a novel solution to antimicrobial resistance (AMR) in view of their unique and broad-spectrum antimicrobial activities. We had recently developed a novel hybrid HDP based on LL-37 and human beta-defensin-2, named CaD23, which was shown to exhibit good in vivo antimicrobial efficacy against Staphylococcus aureus in a bacterial keratitis murine model. This study aimed to examine the potential CaD23-antibiotic synergism and the secondary structure and underlying mechanism of action of CaD23. Methods: Peptide-antibiotic interaction was evaluated against S. aureus, methicillin-resistant S. aureus (MRSA), and Pseudomonas aeruginosa using established checkerboard and time-kill assays. Fractional inhibitory concentration index (FICI) was calculated and interpreted as synergistic (FIC<0.5), additive (FIC between 0.5-1.0), indifferent (FIC between >1.0 and ≤4), or antagonistic (FIC>4). SYTOX green uptake assay was performed to determine the membrane-permeabilising action of CaD23. Molecular dynamics (MD) simulations were performed to evaluate the interaction of CaD23 with bacterial and mammalian mimetic membranes. Circular dichroism (CD) spectroscopy was also performed to examine the secondary structures of CaD23. Results: CaD23-amikacin and CaD23-levofloxacin combination treatment exhibited a strong additive effect against S. aureus SH1000 (FICI = 0.60-0.69) and MRSA43300 (FICI = 0.56-0.60) but an indifferent effect against P. aeruginosa (FIC = 1.03-1.15). CaD23 (at 25 μg/ml; 2xMIC) completely killed S. aureus within 30 min. When used at sub-MIC concentration (3.1 μg/ml; 0.25xMIC), it was able to expedite the antimicrobial action of amikacin against S. aureus by 50%. The rapid antimicrobial action of CaD23 was attributed to the underlying membrane-permeabilising mechanism of action, evidenced by the SYTOX green uptake assay and MD simulations studies. MD simulations revealed that cationicity, alpha-helicity, amphiphilicity and hydrophobicity (related to the Trp residue at C-terminal) play important roles in the antimicrobial action of CaD23. The secondary structures of CaD23 observed in MD simulations were validated by CD spectroscopy. Conclusion: CaD23 is a novel alpha-helical, membrane-active synthetic HDP that can enhance and expedite the antimicrobial action of antibiotics against Gram-positive bacteria when used in combination. MD simulations serves as a powerful tool in revealing the peptide secondary structure, dissecting the mechanism of action, and guiding the design and optimisation of HDPs.
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Affiliation(s)
- Darren Shu Jeng Ting
- Academic Ophthalmology, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Department of Ophthalmology, Queen's Medical Centre, Nottingham, United Kingdom.,Anti-Infectives Research Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Jianguo Li
- Anti-Infectives Research Group, Singapore Eye Research Institute, Singapore, Singapore.,Bioinformatics Institute (AStar), Singapore, Singapore
| | - Chandra S Verma
- Bioinformatics Institute (AStar), Singapore, Singapore.,School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Eunice T L Goh
- Anti-Infectives Research Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Mario Nubile
- Ophthalmic Clinic, University "G d'Annunzio" of Chieti-Pescara, Chieti, Italy
| | | | - Dalia G Said
- Academic Ophthalmology, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Department of Ophthalmology, Queen's Medical Centre, Nottingham, United Kingdom
| | - Roger W Beuerman
- Anti-Infectives Research Group, Singapore Eye Research Institute, Singapore, Singapore
| | | | - Imran Mohammed
- Academic Ophthalmology, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Harminder S Dua
- Academic Ophthalmology, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom.,Department of Ophthalmology, Queen's Medical Centre, Nottingham, United Kingdom
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2
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Mazuryk J, Puchalska I, Koziński K, Ślusarz MJ, Ruczyński J, Rekowski P, Rogujski P, Płatek R, Wiśniewska MB, Piotrowski A, Janus Ł, Skowron PM, Pikuła M, Sachadyn P, Rodziewicz-Motowidło S, Czupryn A, Mucha P. PTD4 Peptide Increases Neural Viability in an In Vitro Model of Acute Ischemic Stroke. Int J Mol Sci 2021; 22:ijms22116086. [PMID: 34200045 PMCID: PMC8200211 DOI: 10.3390/ijms22116086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/23/2021] [Accepted: 05/30/2021] [Indexed: 12/20/2022] Open
Abstract
Ischemic stroke is a disturbance in cerebral blood flow caused by brain tissue ischemia and hypoxia. We optimized a multifactorial in vitro model of acute ischemic stroke using rat primary neural cultures. This model was exploited to investigate the pro-viable activity of cell-penetrating peptides: arginine-rich Tat(49–57)-NH2 (R49KKRRQRRR57-amide) and its less basic analogue, PTD4 (Y47ARAAARQARA57-amide). Our model included glucose deprivation, oxidative stress, lactic acidosis, and excitotoxicity. Neurotoxicity of these peptides was excluded below a concentration of 50 μm, and PTD4-induced pro-survival was more pronounced. Circular dichroism spectroscopy and molecular dynamics (MD) calculations proved potential contribution of the peptide conformational properties to neuroprotection: in MD, Tat(49–57)-NH2 adopted a random coil and polyproline type II helical structure, whereas PTD4 adopted a helical structure. In an aqueous environment, the peptides mostly adopted a random coil conformation (PTD4) or a polyproline type II helical (Tat(49–57)-NH2) structure. In 30% TFE, PTD4 showed a tendency to adopt a helical structure. Overall, the pro-viable activity of PTD4 was not correlated with the arginine content but rather with the peptide’s ability to adopt a helical structure in the membrane-mimicking environment, which enhances its cell membrane permeability. PTD4 may act as a leader sequence in novel drugs for the treatment of acute ischemic stroke.
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Affiliation(s)
- Jarosław Mazuryk
- Laboratory of Neurobiology, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland; (P.R.); (R.P.); (A.C.)
- Department of Electrode Processes, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- Correspondence: (J.M.); (P.M.); Tel.: +48-22-343-2094 (J.M.); +48-58-523-5432 (P.M.)
| | - Izabela Puchalska
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
- Institute of Biotechnology and Molecular Medicine, 80-172 Gdańsk, Poland
| | - Kamil Koziński
- Laboratory of Molecular Neurobiology, Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland; (K.K.); (M.B.W.)
| | - Magdalena J. Ślusarz
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
| | - Jarosław Ruczyński
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
| | - Piotr Rekowski
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
| | - Piotr Rogujski
- Laboratory of Neurobiology, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland; (P.R.); (R.P.); (A.C.)
- NeuroRepair Department, Mossakowski Medical Research Institute PAS, 02-106 Warsaw, Poland
| | - Rafał Płatek
- Laboratory of Neurobiology, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland; (P.R.); (R.P.); (A.C.)
- Laboratory for Regenerative Biotechnology, Gdańsk University of Technology, 80-233 Gdańsk, Poland;
| | - Marta Barbara Wiśniewska
- Laboratory of Molecular Neurobiology, Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland; (K.K.); (M.B.W.)
| | - Arkadiusz Piotrowski
- Department of Biology and Pharmaceutical Botany, Faculty of Pharmacy, Medical University of Gdańsk, 80-416 Gdańsk, Poland;
| | | | - Piotr M. Skowron
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
| | - Michał Pikuła
- Laboratory of Tissue Engineering and Regenerative Medicine, Department of Embryology, Medical University of Gdańsk, 80-210 Gdańsk, Poland;
| | - Paweł Sachadyn
- Laboratory for Regenerative Biotechnology, Gdańsk University of Technology, 80-233 Gdańsk, Poland;
| | - Sylwia Rodziewicz-Motowidło
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
| | - Artur Czupryn
- Laboratory of Neurobiology, Nencki Institute of Experimental Biology PAS, 02-093 Warsaw, Poland; (P.R.); (R.P.); (A.C.)
| | - Piotr Mucha
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (I.P.); (M.J.Ś.); (J.R.); (P.R.); (P.M.S.); (S.R.-M.)
- Correspondence: (J.M.); (P.M.); Tel.: +48-22-343-2094 (J.M.); +48-58-523-5432 (P.M.)
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3
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Hanazono Y, Takeda K, Miki K. Co-translational folding of α-helical proteins: structural studies of intermediate-length variants of the λ repressor. FEBS Open Bio 2018; 8:1312-1321. [PMID: 30087834 PMCID: PMC6070647 DOI: 10.1002/2211-5463.12480] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/17/2018] [Accepted: 06/14/2018] [Indexed: 11/17/2022] Open
Abstract
Nascent polypeptide chains fold cotranslationally, but the atomic‐level details of this process remain unknown. Here, we report crystallographic, de novo modeling, and spectroscopic studies of intermediate‐length variants of the λ repressor N‐terminal domain. Although the ranges of helical regions of the half‐length variant were almost identical to those of the full‐length protein, the relative orientations of these helices in the intermediate‐length variants differed. Our results suggest that cotranslational folding of the λ repressor initially forms a helical structure with a transient conformation, as in the case of a molten globule state. This conformation subsequently matures during the course of protein synthesis. Database Structural data are available in the PDB under the accession numbers http://www.rcsb.org/pdb/search/structidSearch.do?structureId=5ZCA and http://www.rcsb.org/pdb/search/structidSearch.do?structureId=3WOA.
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Affiliation(s)
- Yuya Hanazono
- Department of Chemistry Graduate School of Science Kyoto University Japan.,Present address: Graduate School of Information Sciences Tohoku University Aoba-ku, Sendai 980-8579 Japan
| | - Kazuki Takeda
- Department of Chemistry Graduate School of Science Kyoto University Japan
| | - Kunio Miki
- Department of Chemistry Graduate School of Science Kyoto University Japan
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4
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Joon S, Gopalani M, Rahi A, Kulshreshtha P, Gogoi H, Bhatnagar S, Bhatnagar R. Biochemical characterization of the GTP-sensing protein, CodY of Bacillus anthracis. Pathog Dis 2018; 75:3791465. [PMID: 28472295 DOI: 10.1093/femspd/ftx048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 04/22/2017] [Indexed: 12/30/2022] Open
Abstract
The pleiotropism of the GTP-sensing transcriptional regulator CodY is evident by the gamut of processes that it regulates in almost all low G+C Gram-positive bacteria, including general metabolism, biosynthesis of some amino acids and transport systems, nitrogen uptake, sporulation, biofilm formation, motility and virulence. The role of CodY in virulence has been established in Bacillus anthracis, the top rated bioterrorism agent. In this study, we investigated the biochemical attributes of this global regulator. Homology modeling and sequence/structure analysis revealed putative GTP-binding residues in CodY of B. anthracis. CodY exhibited an interaction with the GTP as tested by ultraviolet cross-linking experiments. It could autophosphorylate itself at a conserved Ser215 residue. This was further corroborated by the impairment of autophosphorylation activity in the CodYS215A mutant. Autophosphorylation may be speculated as an additional mechanism regulating CodY activity in the cell. The protein could also hydrolyze GTP, albeit weakly, as indicated by thin- layer chromatography and spectrophotometric quantification of its kinetic parameters. Altogether, these observations provide us an insight into the mechanism of action of this global regulator and a better understanding of its functional regulation.
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Affiliation(s)
- Shikha Joon
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, Munirka, New Delhi 110067, India.,Structural and Computational Biology Laboratory, Department of Biotechnology, Netaji Subhas Institute of Technology, New Delhi 110078, India
| | - Monisha Gopalani
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, Munirka, New Delhi 110067, India
| | - Amit Rahi
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, Munirka, New Delhi 110067, India
| | | | - Himanshu Gogoi
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, Munirka, New Delhi 110067, India
| | - Sonika Bhatnagar
- Structural and Computational Biology Laboratory, Department of Biotechnology, Netaji Subhas Institute of Technology, New Delhi 110078, India
| | - Rakesh Bhatnagar
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, Munirka, New Delhi 110067, India
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5
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Spagnol G, Al-Mugotir M, Kopanic JL, Zach S, Li H, Trease AJ, Stauch KL, Grosely R, Cervantes M, Sorgen PL. Secondary structural analysis of the carboxyl-terminal domain from different connexin isoforms. Biopolymers 2016; 105:143-62. [PMID: 26542351 DOI: 10.1002/bip.22762] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 10/27/2015] [Accepted: 10/28/2015] [Indexed: 12/19/2022]
Abstract
The connexin carboxyl-terminal (CxCT) domain plays a role in the trafficking, localization, and turnover of gap junction channels, as well as the level of gap junction intercellular communication via numerous post-translational modifications and protein-protein interactions. As a key player in the regulation of gap junctions, the CT presents itself as a target for manipulation intended to modify function. Specific to intrinsically disordered proteins, identifying residues whose secondary structure can be manipulated will be critical toward unlocking the therapeutic potential of the CxCT domain. To accomplish this goal, we used biophysical methods to characterize CxCT domains attached to their fourth transmembrane domain (TM4). Circular dichroism and nuclear magnetic resonance were complementary in demonstrating the connexin isoforms that form the greatest amount of α-helical structure in their CT domain (Cx45 > Cx43 > Cx32 > Cx50 > Cx37 ≈ Cx40 ≈ Cx26). Studies compared the influence of 2,2,2-trifluoroethanol, pH, phosphorylation, and mutations (Cx32, X-linked Charcot-Marie Tooth disease; Cx26, hearing loss) on the TM4-CxCT structure. While pH modestly influences the CT structure, a major structural change was associated with phosphomimetic substitutions. Since most connexin CT domains are phosphorylated throughout their life cycle, studies of phospho-TM4-CxCT isoforms will be critical toward understanding the role that structure plays in regulating gap junction function.
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Affiliation(s)
- Gaëlle Spagnol
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Mona Al-Mugotir
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Jennifer L Kopanic
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Sydney Zach
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Hanjun Li
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Andrew J Trease
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Kelly L Stauch
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Rosslyn Grosely
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Matthew Cervantes
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Paul L Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198
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6
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Structural studies of the N-terminal fragments of the WW domain: Insights into co-translational folding of a beta-sheet protein. Sci Rep 2016; 6:34654. [PMID: 27698466 PMCID: PMC5048162 DOI: 10.1038/srep34654] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 09/16/2016] [Indexed: 11/22/2022] Open
Abstract
Nascent proteins fold co-translationally because the folding speed and folding pathways are limited by the rate of ribosome biosynthesis in the living cell. In addition, though full-length proteins can fold all their residues during the folding process, nascent proteins initially fold only with the N-terminal residues. However, the transient structure and the co-translational folding pathway are not well understood. Here we report the atomic structures of a series of N-terminal fragments of the WW domain with increasing amino acid length. Unexpectedly, the structures indicate that the intermediate-length fragments take helical conformations even though the full-length protein has no helical regions. The circular dichroism spectra and theoretical calculations also support the crystallographic results. This suggests that the short-range interactions are more decisive in the structure formation than the long-range interactions for short nascent proteins. In the course of the peptide extension, the helical structure change to the structure mediated by the long-range interactions at a particular polypeptide length. Our results will provide unique information for elucidating the nature of co-translational folding.
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7
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Pavšič M, Ilc G, Vidmar T, Plavec J, Lenarčič B. The cytosolic tail of the tumor marker protein Trop2--a structural switch triggered by phosphorylation. Sci Rep 2015; 5:10324. [PMID: 25981199 PMCID: PMC4434849 DOI: 10.1038/srep10324] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 04/08/2015] [Indexed: 01/23/2023] Open
Abstract
Trop2 is a transmembrane signaling glycoprotein upregulated in stem and carcinoma cells. Proliferation-enhancing signaling involves regulated intramembrane proteolytic release of a short cytoplasmic fragment, which is later engaged in a cytosolic signaling complex. We propose that Trop2 function is modulated by phosphorylation of a specific serine residue within this cytosolic region (Ser303), and by proximity effects exerted on the cytosolic tail by Trop2 dimerization. Structural characterization of both the transmembrane (Trop2TM) and cytosolic regions (Trop2IC) support this hypothesis, and shows that the central region of Trop2IC forms an α-helix. Comparison of NMR structures of non-phosphorylated and phosphorylated forms suggest that phosphorylation of Trop2IC triggers salt bridge reshuffling, resulting in significant conformational changes including ordering of the C-terminal tail. In addition, we demonstrate that the cytosolic regions of two Trop2 subunits can be brought into close proximity via transmembrane part dimerization. Finally, we show that Ser303-phosphorylation significantly affects the structure and accessibility of functionally important regions of the cytosolic tail. These observed structural features of Trop2 at the membrane-cytosol interface could be important for regulation of Trop2 signaling activity.
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Affiliation(s)
- Miha Pavšič
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Gregor Ilc
- 1] Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia [2] EN-FIST Centre of Excellence, Dunajska 156, SI-1000 Ljubljana, Slovenia
| | - Tilen Vidmar
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Janez Plavec
- 1] Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia [2] Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia [3] EN-FIST Centre of Excellence, Dunajska 156, SI-1000 Ljubljana, Slovenia
| | - Brigita Lenarčič
- 1] Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia [2] J. Stefan Institute, Department of Biochemistry, Molecular and Structural Biology, Jamova 39, SI-1000 Ljubljana, Slovenia
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8
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Kopanic JL, Al-mugotir MH, Kieken F, Zach S, Trease AJ, Sorgen PL. Characterization of the connexin45 carboxyl-terminal domain structure and interactions with molecular partners. Biophys J 2014; 106:2184-95. [PMID: 24853747 PMCID: PMC4052358 DOI: 10.1016/j.bpj.2014.03.045] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 03/19/2014] [Accepted: 03/31/2014] [Indexed: 02/02/2023] Open
Abstract
Mechanisms underlying the initiation and persistence of lethal cardiac rhythms are of significant clinical and scientific interests. Gap junctions are principally involved in forming the electrical connections between myocytes, and changes in distribution, density, and properties are consistent characteristics in arrhythmic heart disease. Therefore, understanding the structure and function of gap junctions during normal and abnormal impulse propagation are essential in the control of arrhythmias. For example, Cx45 is predominately expressed in the specialized myocytes of the impulse generation and conduction system. In both ventricular and atrial human working myocytes, Cx45 is present in very low quantities. However, a reduction in Cx43 coupled with an increased Cx45 protein levels within the ventricles have been observed after myocardial infarction and end-stage heart failure. Cx45 may influence electrical and/or metabolic coupling as a result of pathophysiological overexpression. Our goal was to identify mechanisms that could cause cellular coupling to be different between the cardiac connexins. Based upon the conserved transmembrane and extracellular loop segments, our focus was on identifying features within the divergent cytoplasmic portions. Here, we biophysically characterize the carboxyl-terminal domain of Cx45 (Cx45CT). Purification revealed the possibility of oligomeric species, which was confirmed by analytical ultracentrifugation experiments. Sedimentation equilibrium and circular dichroism studies of different Cx45CT constructs identified one region of α-helical structure (A333-N361) that mediates CT dimerization through hydrophobic contacts. Interestingly, the binding affinity of Cx45CT dimerization is 1000-fold stronger than Cx43CT dimerization. Cx45CT resonance assignments were also used to identify the binding sites and affinities of molecular partners involved in the Cx45 regulation; although none disrupted dimerization, many of these proteins interacted within one intrinsically disordered region (P278-P285). This domain has similarities with other cardiac connexins, and we propose they constitute a master regulatory domain, which contains overlapping molecular partner binding, cis-trans proline isomerization, and phosphorylation sites.
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Affiliation(s)
- Jennifer L Kopanic
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Mona H Al-mugotir
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Fabien Kieken
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Sydney Zach
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Andrew J Trease
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Paul L Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska.
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9
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Spagnol G, Sorgen PL, Spray DC. Structural order in Pannexin 1 cytoplasmic domains. Channels (Austin) 2014; 8:157-66. [PMID: 24751934 DOI: 10.4161/chan.28854] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Pannexin 1 forms ion and metabolite permeable hexameric channels with abundant expression in the central nervous system and elsewhere. Although pannexin 1 does not form intercellular channels, a common channel topology and oligomerization state, as well as involvement of the intracellular carboxyl terminal (CT) domain in channel gating, is shared with connexins. In this study, we characterized the secondary structure of the mouse pannexin 1 cytoplasmic domains to complement structural studies of the transmembrane segments and compare with similar domains from connexins. A combination of structural prediction tools and circular dichroism revealed that, unlike connexins (predominately intrinsically disordered), cytosolic regions of pannexin 1 contain approximately 50% secondary structure, a majority being α-helical. Moreover, prediction of transmembrane domains uncovered a potential membrane interacting region (I360-G370) located upstream of the caspase cleavage site (D375-D378) within the pannexin 1 CT domain. The α-helical content of a peptide containing these domains (G357-S384) increased in the presence of detergent micelles providing evidence of membrane association. We also purified a pannexin 1 CT construct containing the caspase cleavage site (M374-C426), assigned the resonances by NMR, and confirmed cleavage by Caspase-3 in vitro. On the basis of these structural studies of the cytoplasmic domains of pannexin 1, we propose a mechanism for the opening of pannexin 1 channels upon apoptosis, involving structural changes within the CT domain.
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Affiliation(s)
- Gaelle Spagnol
- University of Nebraska Medical Center; Department of Biochemistry and Molecular Biology; Omaha, NE USA
| | - Paul L Sorgen
- University of Nebraska Medical Center; Department of Biochemistry and Molecular Biology; Omaha, NE USA
| | - David C Spray
- Albert Einstein College of Medicine; Rose F. Kennedy Center; Bronx, NY USA
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10
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del Corsso C, Iglesias R, Zoidl G, Dermietzel R, Spray DC. Calmodulin dependent protein kinase increases conductance at gap junctions formed by the neuronal gap junction protein connexin36. Brain Res 2012; 1487:69-77. [PMID: 22796294 PMCID: PMC4355912 DOI: 10.1016/j.brainres.2012.06.058] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/26/2012] [Accepted: 06/30/2012] [Indexed: 11/27/2022]
Abstract
The major neuronal gap junction protein connexin36 (Cx36) exhibits the remarkable property of "run-up", in which junctional conductance typically increases by 10-fold or more within 5-10min following cell break-in with patch pipettes. Such conductance "run-up" is a unique property of Cx36, as it has not been seen in cell pairs expressing other connexins. Because of the recent observation describing CaMKII binding and phosphorylation sites in Cx36 and evidence that calmodulin dependent protein kinase II (CaMKII) may potentiate electrical coupling in neurons of teleosts, we have explored whether CaMKII activates mammalian Cx36. Consistent with this hypothesis, certain Cx36 mutants lacking the CaMKII binding and phosphorylation sites or wild type Cx36 treated with certain cognate peptides corresponding to binding or phosphorylation sites blocked or strongly attenuated run-up of junctional conductance. Likewise, KN-93, an inhibitor of CaMKII, blocked run-up, as did a membrane permeable peptide corresponding to the CaMKII autoinhibitory domain. Furthermore, run-up was blocked by phosphatase delivered within the pipette and not affected by treatment with the phosphatase inhibitor okadaic acid. These results imply that phosphorylation by CaMKII strengthens junctional currents of Cx36 channels, thereby conferring functional plasticity on electrical synapses formed of this protein.
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Affiliation(s)
- Cristiane del Corsso
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY,10461, USA
| | - Rodolfo Iglesias
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY,10461, USA
| | | | | | - David C. Spray
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY,10461, USA
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Shao Q, Liu Q, Lorentz R, Gong XQ, Bai D, Shaw GS, Laird DW. Structure and functional studies of N-terminal Cx43 mutants linked to oculodentodigital dysplasia. Mol Biol Cell 2012; 23:3312-21. [PMID: 22809623 PMCID: PMC3431933 DOI: 10.1091/mbc.e12-02-0128] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mutations in the connexin-43 gap junction protein cause the developmental disease known as oculodentodigital dysplasia. Structure and function approaches are used to demonstrate that the nature of the missense mutation in the amino-terminal domain of connexin-43 governs the mechanism that leads to loss of connexin-43 function. Mutations in the gene encoding connexin-43 (Cx43) cause the human development disorder known as oculodentodigital dysplasia (ODDD). In this study, ODDD-linked Cx43 N-terminal mutants formed nonfunctional gap junction–like plaques and exhibited dominant-negative effects on the coupling conductance of coexpressed endogenous Cx43 in reference cell models. Nuclear magnetic resonance (NMR) protein structure determination of an N-terminal 23–amino acid polypeptide of wild-type Cx43 revealed that it folded in to a kinked α-helical structure. This finding predicted that W4 might be critically important in intramolecular and intermolecular interactions. Thus we engineered and characterized a W4A mutant and found that this mutant formed a regular, nonkinked α-helix but did not form functional gap junctions. Furthermore, a G2V variant peptide of Cx43 showed a kinked helix that now included V2 interactions with W4, resulting in the G2V mutant forming nonfunctional gap junctions. Also predicted from the NMR structures, a G2S mutant was found to relieve these interactions and allowed the protein to form functional gap junctions. Collectively, these studies suggest that the nature of the mutation conveys loss of Cx43 function by distinctly different mechanisms that are rooted in the structure of the N-terminal region.
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Affiliation(s)
- Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
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12
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Locke D, Kieken F, Tao L, Sorgen PL, Harris AL. Mechanism for modulation of gating of connexin26-containing channels by taurine. J Gen Physiol 2011; 138:321-39. [PMID: 21844220 PMCID: PMC3171079 DOI: 10.1085/jgp.201110634] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 07/18/2011] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of action of endogenous modulatory ligands of connexin channels are largely unknown. Previous work showed that protonated aminosulfonates (AS), notably taurine, directly and reversibly inhibit homomeric and heteromeric channels that contain Cx26, a widely distributed connexin, but not homomeric Cx32 channels. The present study investigated the molecular mechanisms of connexin channel modulation by taurine, using hemichannels and junctional channels composed of Cx26 (homomeric) and Cx26/Cx32 (heteromeric). The addition of a 28-amino acid "tag" to the carboxyl-terminal domain (CT) of Cx26 (Cx26(T)) eliminated taurine sensitivity of homomeric and heteromeric hemichannels in cells and liposomes. Cleavage of all but four residues of the tag (Cx26(Tc)) resulted in taurine-induced pore narrowing in homomeric hemichannels, and restored taurine inhibition of heteromeric hemichannels (Cx26(Tc)/Cx32). Taurine actions on junctional channels were fully consistent with those on hemichannels. Taurine-induced inhibition of Cx26/Cx32(T) and nontagged Cx26 junctional channels was blocked by extracellular HEPES, a blocker of the taurine transporter, confirming that the taurine-sensitive site of Cx26 is cytoplasmic. Nuclear magnetic resonance of peptides corresponding to Cx26 cytoplasmic domains showed that taurine binds to the cytoplasmic loop (CL) and not the CT, and that the CT and CL directly interact. ELISA showed that taurine disrupts a pH-dependent interaction between the CT and the CT-proximal half of the CL. These studies reveal that AS disrupt a pH-driven cytoplasmic interdomain interaction in Cx26-containing channels, causing closure, and that the Cx26CT has a modulatory role in Cx26 function.
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Affiliation(s)
- Darren Locke
- Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, USA.
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13
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Grosely R, Kieken F, Sorgen PL. Optimizing the solution conditions to solve the structure of the Connexin43 carboxyl terminus attached to the 4(th) transmembrane domain in detergent micelles. ACTA ACUST UNITED AC 2010; 17:23-33. [PMID: 20513204 DOI: 10.3109/15419061.2010.487956] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
pH-mediated gating of Cx43 channels following an ischemic event is believed to contribute to the development of lethal cardiac arrhythmias. Studies using a soluble version of the Cx43 carboxyl-terminal domain (Cx43CT; S255-I382) have established the central role it plays in channel regulation; however, research in the authors' laboratory suggests that this construct may not be the ideal model system. Therefore, we have developed a more 'native-like' construct (Cx43CT attached to the 4th transmembrane domain [TM4-Cx43CT; G178-I382]) than the soluble Cx43CT to further investigate the mechanism(s) governing this regulation. Here, we utilize circular dichroism and nuclear magnetic resonance (NMR) were used to validate the TM4-Cx43CT for studying channel gating and optimize solution conditions for structural studies. The data indicate that, unlike the soluble Cx43CT, the TM4-Cx43CT is structurally responsive to changes in pH, suggesting the presence of the TM4 facilitates pH-induced structural alterations. Additionally, the optimal solution conditions for solving the NMR solution structure include 10% 2,2,2 trifluoroethanol and removal of the 2nd extracellular loop (G178-V196).
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Affiliation(s)
- Rosslyn Grosely
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA
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Naumenkova TV, Levtsova OV, Nikolaev IN, Shaitan KV. Comparative molecular dynamics study of the structural properties of melittin in water and trifluoroethanol/water. Biophysics (Nagoya-shi) 2010. [DOI: 10.1134/s0006350910010057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Shi Q, Banks EA, Yu XS, Gu S, Lauer J, Fields GB, Jiang JX. Amino acid residue Val362 plays a critical role in maintaining the structure of C terminus of connexin 50 and in lens epithelial-fiber differentiation. J Biol Chem 2010; 285:18415-22. [PMID: 20395299 DOI: 10.1074/jbc.m110.107052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that connexin (Cx) 50, unlike the other two lens connexins, Cx43 and Cx46, promotes chicken lens epithelial-fiber differentiation in a channel-independent manner. Here, we show that deletion of the PEST motif at the C terminus (CT) domain of Cx50 attenuates the stimulatory effect of Cx50 on lens fiber differentiation. Valine 362, a residue located within the PEST domain, is functionally involved. The structure of the Cx50 CT predicted by molecular modeling revealed four alpha-helices and Val(362) was found to be located in the middle of the 3rd helix. Replacement of Val(362) with amino acid residues that disrupt the alpha-helical structure predicted by molecular modeling, such as arginine, glutamate, or phenylalanine, attenuated the stimulatory effects of Cx50 on lens differentiation, whereas replacement with threonine, isoleucine, leucine, or proline, which maintain the structure preserved the function of Cx50. Circular dichroism (CD) studies supported the structural predictions and showed that the substitution with Glu, but not Thr or Pro, disrupted the alpha-helix, which appears to be the structural feature important for lens epithelial-fiber differentiation. Together, our results suggest that Val(362) is important for maintaining the helical structure and is crucial for the role of Cx50 in promoting lens epithelial-fiber differentiation.
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Affiliation(s)
- Qian Shi
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA
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