Intracellular phospho-protein staining techniques for flow cytometry: Monitoring single cell signaling events
Article first published online: 17 SEP 2003
Copyright © 2003 Wiley-Liss, Inc.
Cytometry Part A
Volume 55A, Issue 2, pages 61–70, October 2003
How to Cite
Krutzik, P. O. and Nolan, G. P. (2003), Intracellular phospho-protein staining techniques for flow cytometry: Monitoring single cell signaling events. Cytometry, 55A: 61–70. doi: 10.1002/cyto.a.10072
- Issue published online: 17 SEP 2003
- Article first published online: 17 SEP 2003
- Manuscript Revised: 19 JUN 2003
- Manuscript Accepted: 19 JUN 2003
- Manuscript Received: 11 APR 2003
- National Heart, Lung, and Blood Institute, NIH. Grant Numbers: N01-HV-28183, AI35304
- signaling cascades;
Recent advances in intracellular staining techniques, cytometer technology, fluorescent reagents, and antibody production have expanded the number of intracellular antigens that can be analyzed by flow cytometry. Measurement of protein phosphorylation with phospho-specific antibodies has given insight into kinase signaling cascades. However, available techniques for phospho-epitope staining can differ greatly, making it necessary to understand the differences between the outcomes when such techniques are applied and to develop robust and reproducible methods of application.
Ten different cellular fixation and permeabilization techniques were tested for their ability to provide phospho-specific staining. Combinations of formaldehyde, methanol, ethanol, acetone, Triton X-100, and saponin were used as fixation and permeabilization reagents. Phospho-specific antibodies were labeled with Alexa Fluor dyes to provide multicolor analysis of different signaling events simultaneously within individual cells.
Fixing cells with 1.5% formaldehyde followed by permeabilization in methanol gave optimal results for pERK, pp38, pJNK, pStat1, pStat5, and pStat6 staining. Alteration of formaldehyde fixation and methanol permeabilization times affected measurements of phosphorylation induction. Phospho-specific flow cytometric analyses correlated well with Western blotting, providing cross platform validation of the technique.
Measuring phosphorylation events by flow cytometry provides a rapid and efficient way to measure kinase cascades in individual cells. Stability of phospho-epitopes in methanol allows long-term storage of samples prior to analysis. Multiple signaling cascades can be monitored simultaneously through the use of different fluorophore labels to determine specificity of ligands or inhibitors. Application of optimized techniques to heterogeneous cell types such as peripheral blood or murine splenocytes may allow signaling to be analyzed simultaneously in immune cell subsets. Cytometry Part A 55A:61–70, 2003. © 2003 Wiley-Liss, Inc.