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Raf-1 is required for T cell IL2 production
1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8884.
Abstract:
Engagement of the T cell receptor/CD3 complex activates the serine/threonine kinase, Raf-1, but the physiologic consequences of its activation have not been determined. The effects of Raf-1 on interleukin 2 (IL2) production in T cells were examined using activated and inhibitory forms of Raf-1. A truncated active form of Raf-1 was expressed constitutively from the metallothionein promoter in a malignant T cell line, Jurkat. Treatment of the cells with zinc and cadmium greatly increased active Raf-1 expression. This increase in Raf-1 expression allowed antibodies to CD3 and to CD28 to stimulate IL2 production in the absence of phorbol myristate acetate (PMA) and enhanced IL2 production stimulated by these antibodies in the presence of PMA. The action of active Raf-1 was to increase IL2 gene transcription as it enhanced transcription of a reporter gene linked to IL2 promoter. Finally, the dominant negative form of Raf-1 inhibited transcription directed by the IL2 promoter that was induced by the mitogen phytohemagglutinin (PHA) and PMA. We conclude that Raf-1 activity is necessary for IL2 gene transcription and secretion. These data indicate a role for Raf-1 in the immune response.
Insights
Raf-1 activation is crucial for interleukin 2 (IL2) gene transcription and secretion in T cells, playing a key role in the immune response. This study demonstrates Raf-1
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- Engagement of the T cell receptor/CD3 complex activates the serine/threonine kinase, Raf-1.
- The physiological consequences of Raf-1 activation in T cells, particularly its role in interleukin 2 (IL2) production, were not well understood.
Purpose of the Study:
- To investigate the effects of Raf-1 on IL2 production in T cells.
- To determine the role of Raf-1 in IL2 gene transcription and secretion.
Main Methods:
- Expression of an activated, truncated form of Raf-1 in Jurkat T cells using a metallothionein promoter.
- Stimulation of T cells with antibodies to CD3 and CD28, in the presence and absence of phorbol myristate acetate (PMA).
- Measurement of IL2 production and reporter gene transcription linked to the IL2 promoter.
- Utilized a dominant-negative form of Raf-1 to assess its inhibitory effects on IL2 promoter activity.
Main Results:
- Increased expression of active Raf-1 enhanced IL2 production stimulated by CD3/CD28 antibodies, even without PMA.
- Active Raf-1 increased IL2 gene transcription by enhancing transcription from the IL2 promoter.
- A dominant-negative form of Raf-1 inhibited IL2 promoter-directed transcription induced by phytohemagglutinin (PHA) and PMA.
Conclusions:
- Raf-1 activity is essential for IL2 gene transcription and subsequent secretion.
- These findings establish a significant role for Raf-1 in regulating T cell-mediated immune responses.