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Cyclosporin A specifically inhibits function of nuclear proteins involved in T cell activation
E A Emmel1, C L Verweij, D B Durand
1Howard Hughes Medical Institute, Stanford University, CA 94305.
Abstract:
One action of cyclosporin A thought to be central to many of its immunosuppressive effects is its ability to inhibit the early events of T lymphocyte activation such as lymphokine gene transcription in response to signals initiated at the antigen receptor. Cyclosporin A was found to specifically inhibit the appearance of DNA binding activity of NF-AT, AP-3, and to a lesser extent NF-kappa B, nuclear proteins that appear to be important in the transcriptional activation of the genes for interleukin-2 and its receptor, as well as several other lymphokines. In addition, cyclosporin A abolished the ability of the NF-AT binding site to activate a linked promoter in transfected mitogen-stimulated T lymphocytes and in lymphocytes from transgenic mice. These results indicate that cyclosporin A either directly inhibits the function of nuclear proteins critical to T lymphocyte activation or inhibits the action of a more proximal member of the signal transmission cascade leading from the antigen receptor to the nucleus.
Insights
Cyclosporin A inhibits T lymphocyte activation by blocking key nuclear proteins like NF-AT. This drug interferes with lymphokine gene transcription, crucial for immune responses.
Area of Science:
- Immunology
- Molecular Biology
- Pharmacology
Background:
- Cyclosporin A is a key immunosuppressant drug.
- Its mechanism involves inhibiting T lymphocyte activation.
- Early T cell activation is critical for immune responses.
Purpose of the Study:
- To investigate the molecular targets of Cyclosporin A in T lymphocyte activation.
- To elucidate how Cyclosporin A affects nuclear factor binding and gene transcription.
Main Methods:
- Assessing DNA-binding activity of nuclear proteins (NF-AT, AP-3, NF-kappa B).
- Using reporter gene assays in transfected T lymphocytes and transgenic mice models.
- Evaluating the impact of Cyclosporin A on signal transduction pathways.
Main Results:
- Cyclosporin A specifically inhibited the DNA-binding activity of NF-AT and AP-3, and to a lesser extent NF-kappa B.
- The drug abolished the activating function of the NF-AT binding site in reporter gene assays.
- These nuclear factors are crucial for the transcription of interleukin-2 and other lymphokines.
Conclusions:
- Cyclosporin A interferes with the transcriptional activation of lymphokine genes.
- The drug likely acts by directly inhibiting critical nuclear proteins or upstream signaling components.
- This provides a molecular basis for Cyclosporin A's immunosuppressive effects in T cell activation.