Abstract
Halide-sensitive fluorescent indicators have been useful in cystic fibrosis (CF) research in assaying functional cystic fibrosis transmembrane conductance regulator (CFTR) expression in cells. Some applications (for review, see refs. 1 and 2) have included measurements in native airway cells (3), demonstration that CFTR is a chloride channel (4,5), functional analysis of mutant CFTRs (6-8), and analysis of the efficacy of CFTR gene replacement in human gene therapy trials (9-11). A promising new application of halide indicators is in high-throughput screening to discover drugs that may correct defective cellular processing and/or function of disease-causing CFTR mutants. Another new application is the use of cell-impermeable chloride indicators to measure chloride concentration in the airway surface liquid in cell culture models and in the in vivo trachea (12). The first biological application of a chloride indicator, SPQ, was reported in 1987 (13). As described below, numerous advances in indicator technology have been made since the first report, including the development of cell-permeable (14), cell-impermeable (15,16), long-wavelength (17,18), and dual-wavelength (19) indicators, as well as the development of a targetable green fluorescent protein-based halide indicator (20). The major advantages of a fluorescence-based assay of CFTR function are sensitivity, technical simplicity, and the ability to assay function in single cells and heterogeneous cell mixtures. Fluorescence assays are rapid, quantitative, and technically simple, and can be performed using fluorescence microscopy, automated fluorescence plate readers, or cell cytometry. In contrast, assays using radioactive 36Cl require relatively large amounts of materials, are technically difficult, and cannot be used to study single cells or heterogeneous cell mixtures. Single-channel electrophysiological measurements of CFTR function are also technically challenging and generally not suitable for screening applications; however, it should be noted that data on single-channel properties (open probability, gating kinetics, current-voltage relationships) cannot be obtained by fluorescence methods. This chapter describes the available fluorescence-based assays of CFTR function. Technical details and useful practical hints are provided, and potential pitfalls are mentioned.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Verkman, A. S. (1990) Development and biological applications of chloride-sensitive fluorescent indicators. Am. J. Physiol. 259, C375āC388.
Verkman, A. S. and Biwersi, J. (1995) Chloride-sensitive fluorescent indicators, in Methods in Neurosciences, Vol. 27. (Kraicer, J. and Dixon, S. J., eds.), Academic Press, pp. 328ā339.
Verkman, A. S., Chao, A. C.. and Hartmann, T. (1992) Hormonal regulation of chloride conductance in cultured polar airway cells measured by a fluorescent indicator. Am. J. Physiol. 262, C23āC31.
Cheng, S. H., Rich, D. P., Marshall, J., Gregory, R. J., Welsh, M. J., and Smith, A. E. (1991) Phosphorylation of the R domain by cAMP-dependent protein kinase regulates the CFTR chloride channel. Cell 66, 1027ā1036.
Rommens, J. M., Dho, S., Bear, C. E., Kartner, N., Kennedy, D., Riordan, J. R., Tsui, L. C., and Foskett, J. K. (1991) cAMP-inducible chloride conductance in mouse fibroblast lines stably expressing the human cystic fibrosis transmembrane conductance regulator. Proc. Natl. Acad. Sci. USA 88, 7500ā7505.
Brown, R., Hong-Brown, L., Biwersi, J., Verkman, A. S., and Welch, W. (1996) Chemical chaperones correct the mutant phenotype of the DF508 cystic fibrosis transmembrane conductance regulator protein. Cell Stress Chaperones 1, 117ā125.
Cheng, S. H., Fang, S. L., Zabner, J., Marshall, J., Piraino, S., Schiavi, S. C., et al. (1995) Functional activation of the cystic fibrosis trafficking mutant DF508-CFTR by overexpression. Am. J. Physiol. 268, L615āL624.
Rich, D. P., Anderson, M. P., Gregory, R. J., Cheng, S. H., Paul, S., Jefferson, D. M., et al. (1990) Expression of cystic fibrosis transmembrane conductance regulator corrects defective chloride channel regulation in cystic fibrosis airway epithelial cells. Nature 347, 358ā363.
Mansoura, M., Biwersi, J., Ashlock, M., and Verkman, A. S. (1999) Fluorescent chloride indicators to assess the efficacy of CFTR cDNA delivery. Human Gene Therapy 10, 861ā875.
Porteous, D. J., Dorin, J. R., McLachlan, G., Davidson-Smith, H., Davidson, H., Stevenson, B. J., et al. (1997) Evidence for safety and efficacy of DOTAP cat-ionic liposome mediated CFTR gene transfer to the nasal epithelium of patients with cystic fibrosis. Gene Ther. 4, 210ā218.
Gill, D. R., Southern, K. W., Mofford, K. A., Seddon, T., Huang, L., Sorgi, F., et al. (1997) A placebo-controlled study of liposome-mediated gene transfer to the nasal epithelium of patients with cystic fibrosis. Gene Ther. 4, 199ā209.
Jayaraman, S., Song, Y., Vetrivel, L., Shankar, L., and Verkman, A. S. (2001) Non-invasive in vivo fluorescence measurement of airway surface liquid depth, salt concentration and pH. J. Clin. Invest. 107, 317ā324.
Illsley, N. P. and Verkman, A. S. (1987) Membrane chloride transport measured using a chloride-sensitive fluorescent indicator. Biochemistry 26, 1215ā1219.
Biwersi, J. and Verkman, A. S. (1991) Cell permeable fluorescent indicator for cytosolic chloride. Biochemistry 30, 7879ā7883.
Biwersi, J., Farah, N. Wang, Y. X. Ketchum, R., and Verkman, A. S. (1992) Synthesis of cell-impermeable Cl-sensitive fluorescent indicators with improved sensitivity and optical properties. Am. J. Physiol. 262, C243āC250.
Verkman, A. S., Sellers, M., Chao, A. C., Leung, T., and Ketcham, R. (1989) Synthesis and characterization of improved chloride-sensitive fluorescent indicators for biological applications. Anal. Biochem. 178, 355ā361.
Biwersi, J., Tulk, B., and Verkman, A. S. (1994) Long wavelength chloride-sensitive fluorescent indicators. Anal. Biochem. 219, 139ā143.
Jayaraman, S., Teitler, L., Skalski, B., and Verkman, A. S. (1999) Long-wavelength iodide-sensitive fluorescent indicators for measurement of functional CFTR expression in cells. Am. J. Physiol. 277, C1008āC1018.
Jayaraman, S., Biwersi, J., and Verkman A. S. (1999) Synthesis and characteriza-tion of dual-wavelength chloride sensitive fluorescent indicators for ratio imaging. Am. J. Physiol. 276, C747āC757.
Jayaraman, S., Haggie, P., Wachter, R., Remington, S. J., and Verkman, A. S. (2000) Mechanism and cellular applications of a green fluorescent protein-based halide sensor. J. Biol. Chem. 275, 6047ā6050.
Jayaraman, S. and Verkman, A. S. (2000) Charge transfer mechanism for quenching of quinolinium fluorescence by halides. Biophys. Chem. 85, 49ā57.
Haggie, P., Jayaraman, S., and Verkman, A. S. (2001) Ratioable GFP-based halide indicators utilizing a novel energy transfer strategy. Biophys. J. 80, 654a.
Galietta, L. J. V., Haggie, P. M., and Verkman, A. S. (2001) Green fluorescent protein-based halide indicators with improved chloride and iodide affnities. FEBS Lett. 499, 220ā224.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
Ā© 2002 Humana Press Inc.
About this protocol
Cite this protocol
Verkman, A.S., Jayaraman, S. (2002). Fluorescent Indicator Methods to Assay Functional CFTR Expression in Cells. In: Skach, W.R. (eds) Cystic Fibrosis Methods and Protocols. Methods in Molecular Medicineā¢, vol 70. Humana Press. https://doi.org/10.1385/1-59259-187-6:187
Download citation
DOI: https://doi.org/10.1385/1-59259-187-6:187
Publisher Name: Humana Press
Print ISBN: 978-0-89603-897-4
Online ISBN: 978-1-59259-187-9
eBook Packages: Springer Protocols