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Investigation of 1-Methylcytosine as a Ligand in Gold(III) Complexes: Synthesis and Protein Interactions. INORGANICS 2018. [DOI: 10.3390/inorganics7010001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The HIV nucleocapsid protein NCp7 was previously shown to play a number of roles in the viral life cycle and was previously identified as a potential target for small molecule intervention. In this work, the synthesis of the previously unreported complexes [Au(dien)(1MeCyt)]3+, [Au(N-Medien)(1MeCyt)]3+, and [Au(dien)(Cyt)]3+ is detailed, and the interactions of these complexes with the models for NCp7 are described. The affinity for these complexes with the target interaction site, the “essential” tryptophan of the C-terminal zinc finger motif of NCp7, was investigated through the use of a fluorescence quenching assay and by 1H-NMR spectroscopy. The association of [Au(dien)(1MeCyt)]3+ as determined through fluorescence quenching is intermediate between the previously reported DMAP and 9-EtGua analogs, while the associations of [Au(N-Medien)(1MeCyt)]3+ and [Au(dien)(Cyt)]3+ are lower than the previously reported complexes. Additionally, NMR investigation shows that the self-association of relevant compounds is negligible. The specifics of the interaction with the C-terminal zinc finger were investigated by circular dichroism spectroscopy and electrospray-ionization mass spectrometry. The interaction is complete nearly immediately upon mixing, and the formation of AuxFn+ (x = 1, 2, or 4; F = apopeptide) concomitant with the loss of all ligands is observed. Additionally, oxidized dimerized peptide was observed for the first time as a product, indicating a reaction via a charge transfer mechanism.
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Heng S, Zhang X, Pei J, Adwal A, Reineck P, Gibson BC, Hutchinson MR, Abell AD. Spiropyran-Based Nanocarrier: A New Zn 2+ -Responsive Delivery System with Real-Time Intracellular Sensing Capabilities. Chemistry 2018; 25:854-862. [PMID: 30414294 DOI: 10.1002/chem.201804816] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Indexed: 11/10/2022]
Abstract
A new spiropyran-based stimuli-responsive delivery system is fabricated. It encapsulates and then releases an extraneous compound in response to elevated levels of Zn2+ , a critical factor in cell apoptosis. A C12 -alkyl substituent on the spiropyran promotes self-assembly into a micelle-like nanocarrier in aqueous media, with nanoprecipitation and encapsulation of added payload. Zn2+ binding occurs to an appended bis(2-pyridylmethyl)amine group at biologically relevant micromolar concentration. This leads to switching of the spiropyran (SP) isomer to the strongly fluorescent ring opened merocyanine-Zn2+ (MC-Zn2+ ) complex, with associated expansion of the nanocarriers to release the encapsulated payload. Payload release is demonstrated in solution and in HEK293 cells by encapsulation of a blue fluorophore, 7-hydroxycoumarin, and monitoring its release using fluorescence spectroscopy and microscopy. Furthermore, the use of the nanocarriers to deliver a caspase inhibitor, Azure B, into apoptotic cells in response to an elevated Zn2+ concentration is demonstrated. This then inhibits intracellular caspase activity, as evidenced by confocal microscopy and in real-time by time-lapsed microscopy. Finally, the nanocarriers are shown to release an encapsulated proteasome inhibitor (5) in Zn2+ -treated breast carcinoma cell line models. This then inhibits intracellular proteasome and induces cytotoxicity to the carcinoma cells.
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Affiliation(s)
- Sabrina Heng
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,Department of Chemistry, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Xiaozhou Zhang
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,Department of Chemistry, The University of Adelaide, Adelaide, South Australia, 5005, Australia
| | - Jinxin Pei
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,Department of Physiology, Adelaide Medical School, The University of Adelaide, South Australia, Australia
| | - Alaknanda Adwal
- The Robinson Research Institute, Adelaide Medical School, The University of Adelaide, Adelaide, SA, 5005, Australia
| | - Philipp Reineck
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,CNBP, School of Science, RMIT University, Melbourne, Victoria, 3001, Australia
| | - Brant C Gibson
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,CNBP, School of Science, RMIT University, Melbourne, Victoria, 3001, Australia
| | - Mark R Hutchinson
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,Department of Physiology, Adelaide Medical School, The University of Adelaide, South Australia, Australia
| | - Andrew D Abell
- ARC Center of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, The University of Adelaide, Australia.,Department of Chemistry, The University of Adelaide, Adelaide, South Australia, 5005, Australia
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Eron SJ, MacPherson DJ, Dagbay KB, Hardy JA. Multiple Mechanisms of Zinc-Mediated Inhibition for the Apoptotic Caspases-3, -6, -7, and -8. ACS Chem Biol 2018; 13:1279-1290. [PMID: 29364645 PMCID: PMC5959779 DOI: 10.1021/acschembio.8b00064] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Zinc is emerging as a widely used and important biological regulatory signal. Cellular zinc levels are tightly regulated by a complex array of zinc importers and exporters to control processes such as apoptotic cell death. While caspase inhibition by zinc has been reported previously, the reported inhibition constants were too weak to suggest a critical biological role for zinc-mediated inhibition. In this work, we have adopted a method of assessing available zinc. This allowed assessment of accurate inhibition constants for apoptotic caspases, caspase-3, -6, -7, and -8. Each of these caspases are inhibited by zinc at intracellular levels but with widely differing inhibition constants and different zinc binding stoichiometries. Caspase-3, -6, and -8 appear to be constitutively inhibited by typical zinc levels, and this inhibition must be lifted to allow activation. The inhibition constant for caspase-7 (76 nM) is much weaker than for the other apoptotic caspases (2.6-6.9 nM) suggesting that caspase-7 is not inactivated by normal zinc concentrations but can be inhibited under conditions of zinc stress. Caspase-3, -7, and -8 were found to bind three, one, and two zincs, respectively. In each of these caspases, zinc was present in the active site, in contrast to caspase-6, which binds one zinc allosterically. The most notable new mechanism to emerge from this work is for zinc-mediated inhibition of caspase-8. Zinc binds caspase-8 directly at the active site and at a second site. Zinc binding inhibits formation of the caspase-8 dimer, the activated form of the enzyme. Together these findings suggest that zinc plays a critical role in regulation of apoptosis by direct inactivation of caspases, in a manner that is unique for each caspase.
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Affiliation(s)
- Scott J. Eron
- Department of Chemistry, 104 LGRT, 710 N. Pleasant St. University of Massachusetts Amherst, MA 01003, USA
| | - Derek J. MacPherson
- Department of Chemistry, 104 LGRT, 710 N. Pleasant St. University of Massachusetts Amherst, MA 01003, USA
| | - Kevin B. Dagbay
- Department of Chemistry, 104 LGRT, 710 N. Pleasant St. University of Massachusetts Amherst, MA 01003, USA
| | - Jeanne A. Hardy
- Department of Chemistry, 104 LGRT, 710 N. Pleasant St. University of Massachusetts Amherst, MA 01003, USA
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