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Anttila MM, Vickerman BM, Wang Q, Lawrence DS, Allbritton NL. Photoactivatable Reporter to Perform Multiplexed and Temporally Controlled Measurements of Kinase and Protease Activity in Single Cells. Anal Chem 2021; 93:16664-16672. [PMID: 34865468 PMCID: PMC8753264 DOI: 10.1021/acs.analchem.1c04225] [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: 12/16/2022]
Abstract
Peptide bioreporters were developed to perform multiplexed measurements of the activation of epidermal growth factor receptor kinase (EGFR), Akt kinase (Akt/protein kinase B), and proteases/peptidases in single cells. The performance characteristics of the three reporters were assessed by measuring the reporter's proteolytic stability, kinetic constants for EGFR and Akt, and dephosphorylation rate. The reporter displaying optimal performance was composed of 6-carboxyfluorescein (6-FAM) on the peptide N-terminus, an Akt substrate sequence employing a threonine phosphorylation site for Akt, followed by a tri-D arginine linker, and finally an EGFR substrate sequence bearing a phosphatase-resistant 7-(S)-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (L-htc) residue as the EGFR phosphorylation site. Importantly, use of a single electrophoretic condition separated the mono- and diphosphorylated products as well as proteolytic forms permitting the quantitation of multiple enzyme activities simultaneously using a single reporter. Because the Akt and EGFR substrates were linked, a known ratio (EGFR/Akt) of the reporter was loaded into cells. A photoactivatable version of the reporter was synthesized by adding two 4,5-dimethoxy-2-nitrobenzyl (DMNB) moieties to mask the EGFR and Akt phosphorylation sites. The DMNB moieties were readily photocleaved following exposure to 360 nm light, unmasking the phosphorylation sites on the reporter. The new photoactivatable reporter permitted multiplexed measurements of kinase signaling and proteolytic degradation in single cells in a temporally controlled manner. This work will facilitate the development of a new generation of multiplexed activity-based reporters capable of light-initiated measurement of enzymatic activity in single cells.
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Affiliation(s)
- Matthew M. Anttila
- Department of Chemistry, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
- Department of Bioengineering, University of Washington, Seattle, Washington, 98125
| | - Brianna M. Vickerman
- Department of Chemistry, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Qunzhao Wang
- Division of Chemical Biology and Medicinal Chemistry UNC Eshelman School of Pharmacy, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - David S. Lawrence
- Department of Chemistry, Chapel Hill, North Carolina 27599
- Division of Chemical Biology and Medicinal Chemistry UNC Eshelman School of Pharmacy, Chapel Hill, North Carolina 27599
- Department of Pharmacology, School of Medicine, Chapel Hill, North Carolina 27599
- The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Nancy L. Allbritton
- Department of Bioengineering, University of Washington, Seattle, Washington, 98125
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Abraham DH, Anttila MM, Gallion LA, Petersen BV, Proctor A, Allbritton NL. Design of an automated capillary electrophoresis platform for single-cell analysis. Methods Enzymol 2019; 628:191-221. [PMID: 31668230 DOI: 10.1016/bs.mie.2019.06.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Single-cell analysis of cellular contents by highly sensitive analytical instruments is known as chemical cytometry. A chemical cytometer typically samples one cell at a time, quantifies the cellular contents of interest, and then processes and reports that data. Automation adds the potential to perform this entire sequence of events with minimal intervention, increasing throughput and repeatability. In this chapter, we discuss the design considerations for an automated capillary electrophoresis-based instrument for assay of enzymatic activity within single cells. We describe the key requirements of the microscope base and capillary electrophoresis platforms. We also provide detailed protocols and schematic designs of our cell isolation, lysis, sampling, and detection strategies. Additionally, we describe our signal processing and instrument automation workflows. The described automated system has demonstrated single-cell throughput at rates above 100cells/h and analyte limits of detection as low as 10-20mol.
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Affiliation(s)
- David H Abraham
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Matthew M Anttila
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Luke A Gallion
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Brae V Petersen
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Nancy L Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States; Joint Department of Biomedical Engineering, University of North Carolina, Chapel and North Carolina State University, Raleigh, NC, USA.
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Proctor A, Allbritton NL. "Fix and assay": separating in-cellulo sphingolipid reactions from analytical assay in time and space using an aldehyde-based fixative. Analyst 2019; 144:961-971. [PMID: 30207332 DOI: 10.1039/c8an01353e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Chemical cytometry using capillary electrophoresis (CE) is a powerful tool for measuring single-cell enzyme activity. However, these measurements are often confounding as dynamic processes within cells rapidly change depending on environment, meaning that cell handling, transport, and storage can affect signaling pathways and alter results. To meet these challenges, we describe a method utilizing aldehyde fixation to simultaneously terminate cellular reactions across a population, freezing reaction results in time prior to analytical analysis. Fluorescent sphingosine was loaded into cells of different lineages (leukemia and lymphoma cell lines and primary leukemia cells) and allowed to react before fixing. The remaining sphingosine and any products formed were then quantified with chemical cytometry utilizing CE. When cells were loaded with sphingosine followed by glyoxal fixation and immediate analysis, 55 ± 5% of lipid was recoverable compared to an unfixed control. Storage of fixed cells for 24 h showed no statistical differences in total amount of recoverable sphingolipid compared to samples analyzed immediately after fixation-though there was a difference in recovery of low-abundance products. Sphingosine kinase activity decreased in response to inhibitor treatment compared to treatment with a DMSO vehicle (21 ± 3% product formed in inhibitor-treated cells vs. 57 ± 2% in control cells), which was mirrored in single-cell measurements. This "fix and assay" strategy enables measurement of sphingosine kinase activity in single cells followed by subsequent analytical assay separated in space and time from reaction initiation, enabling greater temporal control over intracellular reactions and improving future compatibility with clinical workflow.
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Affiliation(s)
- Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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Proctor A, Wang Q, Lawrence DS, Allbritton NL. Selection and optimization of enzyme reporters for chemical cytometry. Methods Enzymol 2019; 622:221-248. [PMID: 31155054 PMCID: PMC6905852 DOI: 10.1016/bs.mie.2019.02.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chemical cytometry, sensitive analytical measurements of single cells, reveals inherent heterogeneity of cells within a population which is masked or averaged out when using bulk analysis techniques. A particular challenge of chemical cytometry is the development of a suitable reporter or probe for the desired measurement. These reporters must be sufficiently specific for measuring the desired process; possess a lifetime long enough to accomplish the measurement; and have the ability to be loaded into single cells. This chapter details our approach to rationally design and improve peptide substrates as reporters of enzyme activity utilizing chemical cytometry. This method details the iterative approach used to design, characterize, and identify a peptidase-resistant peptide reporter which acts as a kinase substrate within intact cells. Small-scale, rationally designed peptide libraries are generated to rapidly and economically screen candidate reporter peptides for substrate suitability and peptidase resistance. Also detailed are strategies to characterize and validate the designed reporters by determining kinetic parameters, intracellular substrate specificity, resistance to degradation by intracellular peptidases, and behavior within lysates and intact cells.
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Affiliation(s)
- Angela Proctor
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States
| | - Qunzhao Wang
- Department of Chemical Biology and Medicinal Chemistry, School of Pharmacy, University of North Carolina, Chapel Hill, NC, United States
| | - David S Lawrence
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States; Department of Chemical Biology and Medicinal Chemistry, School of Pharmacy, University of North Carolina, Chapel Hill, NC, United States
| | - Nancy L Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC, United States; Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill; North Carolina State University, Raleigh, NC, United States.
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Vickerman BM, Anttila MM, Petersen BV, Allbritton NL, Lawrence DS. Design and Application of Sensors for Chemical Cytometry. ACS Chem Biol 2018; 13:1741-1751. [PMID: 29376326 DOI: 10.1021/acschembio.7b01009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The bulk cell population response to a stimulus, be it a growth factor or a cytotoxic agent, neglects the cell-to-cell variability that can serve as a friend or as a foe in human biology. Biochemical variations among closely related cells furnish the basis for the adaptability of the immune system but also act as the root cause of resistance to chemotherapy by tumors. Consequently, the ability to probe for the presence of key biochemical variables at the single-cell level is now recognized to be of significant biological and biomedical impact. Chemical cytometry has emerged as an ultrasensitive single-cell platform with the flexibility to measure an array of cellular components, ranging from metabolite concentrations to enzyme activities. We briefly review the various chemical cytometry strategies, including recent advances in reporter design, probe and metabolite separation, and detection instrumentation. We also describe strategies for improving intracellular delivery, biochemical specificity, metabolic stability, and detection sensitivity of probes. Recent applications of these strategies to small molecules, lipids, proteins, and other analytes are discussed. Finally, we assess the current scope and limitations of chemical cytometry and discuss areas for future development to meet the needs of single-cell research.
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Affiliation(s)
- Brianna M. Vickerman
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Matthew M. Anttila
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Brae V. Petersen
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Nancy L. Allbritton
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, and North Carolina State University,
Raleigh, North Carolina 27695, United States
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - David S. Lawrence
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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St. Louis LE, Rodriguez TM, Waters ML. A study of 2-component i, i + 3 peptide stapling using thioethers. Bioorg Med Chem 2018; 26:1203-1205. [DOI: 10.1016/j.bmc.2017.10.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 10/20/2017] [Accepted: 10/28/2017] [Indexed: 10/18/2022]
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