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Yin Y, Zhao SL, Rane D, Lin Z, Wu M, Peterson BR. Quantification of Binding of Small Molecules to Native Proteins Overexpressed in Living Cells. J Am Chem Soc 2024; 146:187-200. [PMID: 38118119 PMCID: PMC10910633 DOI: 10.1021/jacs.3c07488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The affinity and selectivity of small molecules for proteins drive drug discovery and development. We report a fluorescent probe cellular binding assay (FPCBA) for determination of these values for native (untagged) proteins overexpressed in living cells. This method uses fluorophores such as Pacific Blue (PB) linked to cell-permeable protein ligands to generate probes that rapidly and reversibly equilibrate with intracellular targets, as established by kinetic assays of cellular uptake and efflux. To analyze binding to untagged proteins, an internal ribosomal entry site (IRES) vector was employed that allows a single mRNA to encode both the protein target and a separate orthogonal fluorescent protein (mVenus). This enabled cellular uptake of the probe to be correlated with protein expression by flow cytometry, allowing measurement of cellular dissociation constants (Kd) of the probe. This approach was validated by studies of the binding of allosteric activators to eight different Protein Kinase C (PKC) isozymes. Full-length PKCs expressed in transiently transfected HEK293T cells were used to measure cellular Kd values of a probe comprising PB linked to the natural product phorbol via a carbamate. These values were further used to determine competitive binding constants (cellular Ki values) of the nonfluorescent phorbol ester PDBu and the anticancer agent bryostatin 1 for each isozyme. For some PKC-small molecule pairs, these cellular Ki values matched known biochemical Ki values, but for others, altered selectivity was observed in cells. This approach can facilitate quantification of interactions of small molecules with physiologically relevant native proteins.
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Affiliation(s)
- Yuwen Yin
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, College of Pharmacy, 500 W. 12 Ave., Columbus, OH 43210, USA
| | - Serena Li Zhao
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, College of Pharmacy, 500 W. 12 Ave., Columbus, OH 43210, USA
| | - Digamber Rane
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, College of Pharmacy, 500 W. 12 Ave., Columbus, OH 43210, USA
| | - Zhihong Lin
- The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, 460 W. 10 Ave., Columbus, OH 43210, USA
| | - Meng Wu
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, College of Pharmacy, 500 W. 12 Ave., Columbus, OH 43210, USA
- The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, 460 W. 10 Ave., Columbus, OH 43210, USA
| | - Blake R. Peterson
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University, College of Pharmacy, 500 W. 12 Ave., Columbus, OH 43210, USA
- The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, 460 W. 10 Ave., Columbus, OH 43210, USA
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Wojciechowski MN, Schreiber S, Jose J. A Novel Flow Cytometry-Based Assay for the Identification of HCN4 CNBD Ligands. Pharmaceuticals (Basel) 2023; 16:ph16050710. [PMID: 37242492 DOI: 10.3390/ph16050710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/25/2023] [Accepted: 05/03/2023] [Indexed: 05/28/2023] Open
Abstract
Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are promising therapeutic targets because of their association with the genesis of several diseases. The identification of selective compounds that alter cAMP-induced ion channel modulation by binding to the cyclic nucleotide-binding domain (CNBD) will facilitate HCN channel-specific drug development. In this study, a fast and protein purification-free ligand-binding approach with a surface-displayed HCN4 C-Linker-CNBD on E. coli is presented. 8-Fluo-cAMP ligand binding was monitored by single-cell analysis via flow cytometry, and a Kd-value of 173 ± 46 nM was determined. The Kd value was confirmed by ligand depletion analysis and equilibrium state measurements. Applying increasing concentrations of cAMP led to a concentration-dependent decrease in fluorescence intensity, indicating a displacement of 8-Fluo-cAMP. A Ki-value of 8.5 ± 2 µM was determined. The linear relationship of IC50 values obtained for cAMP as a function of ligand concentration confirmed the competitive binding mode: IC50: 13 ± 2 µM/16 ± 3 µM/23 ± 1 µM/27 ± 1 µM for 50 nM/150 nM/250 nM/500 nM 8-Fluo-cAMP. A similar competitive mode of binding was confirmed for 7-CH-cAMP, and an IC50 value of 230 ± 41 nM and a Ki of 159 ± 29 nM were determined. Two established drugs were tested in the assay. Ivabradine, an approved HCN channel pore blocker and gabapentin, is known to bind to HCN4 channels in preference to other isoforms with an unknown mode of action. As expected, ivabradine had no impact on ligand binding. In addition, gabapentin had no influence on 8-Fluo-cAMP's binding to HCN4-CNBD. This is the first indication that gabapentin is not interacting with this part of the HCN4 channel. The ligand-binding assay as described can be used to determine binding constants for ligands such as cAMP and derivatives. It could also be applied for the identification of new ligands binding to the HCN4-CNBD.
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Affiliation(s)
- Magdalena N Wojciechowski
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
| | - Sebastian Schreiber
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
| | - Joachim Jose
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, Pharmacampus, 48149 Münster, Germany
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O’Boyle NM, Helesbeux JJ, Meegan MJ, Sasse A, O’Shaughnessy E, Qaisar A, Clancy A, McCarthy F, Marchand P. 30th Annual GP2A Medicinal Chemistry Conference. Pharmaceuticals (Basel) 2023; 16:ph16030432. [PMID: 36986531 PMCID: PMC10056312 DOI: 10.3390/ph16030432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/16/2023] [Indexed: 03/14/2023] Open
Abstract
The Group for the Promotion of Pharmaceutical Chemistry in Academia (GP2A) held their 30th annual conference in August 2022 in Trinity College Dublin, Ireland. There were 9 keynote presentations, 10 early career researcher presentations and 41 poster presentations.
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Affiliation(s)
- Niamh M. O’Boyle
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
- Correspondence: ; Tel.: +353-1896-2524
| | | | - Mary J. Meegan
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Astrid Sasse
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Elizabeth O’Shaughnessy
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Alina Qaisar
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Aoife Clancy
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Florence McCarthy
- School of Chemistry and ABCRF, University College Cork, T12 K8AF Cork, Ireland
| | - Pascal Marchand
- Cibles et Médicaments des Infections et de l’Immunité, IICiMed, Nantes Université, UR 1155, F-44000 Nantes, France
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