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Interleukin-4 activates two distinct pathways of phosphatidylinositol-3 kinase in the same cells
1Department of Immunology, DNAX Research Institute of Molecular and Cellular Biology, Inc., Palo Alto, California 94304-1104, USA.
Abstract:
We have recently demonstrated that c-fes protooncogene product (FES), or a FES-related protein, associates with the interleukin-4 receptor alpha chain (IL-4R alpha) and phosphatidylinositol-3 (PI3) kinase in mouse T cell lines; however, others have demonstrated that PI3 kinase associates with IL-4R alpha through tyrosine phosphorylated insulin receptor substrate (IRS)-2 in other cell types. In order to examine whether IL-4 activates these two distinct PI3 kinase pathways in the same cells, we analyzed association of PI3 kinase with IRS-2, and tyrosine phosphorylation of IRS-2, in a mouse pro-B cell line, Ba/F3, and a mouse mast cell line, MC9. In both cell lines, IL-4 induced tyrosine phosphorylation of IRS-2, association of PI3 kinase with IRS-2, and FES or a FES-related protein. These results indicate that IL-4 activates two distinct PI3 kinase pathways in the same cells. We further identified the critical region in the cytoplasmic domain of IL-4R alpha required for tyrosine phosphorylation of IRS-2.
Insights
Interleukin-4 (IL-4) activates two distinct phosphatidylinositol-3 (PI3) kinase pathways in immune cells. This involves both FES protein and insulin receptor substrate-2 (IRS-2) interactions with the IL-4 receptor alpha chain.
Area of Science:
- Immunology
- Cell Signaling
- Molecular Biology
Background:
- The interleukin-4 receptor alpha chain (IL-4Rα) is crucial for immune cell signaling.
- Distinct pathways involving FES protein and insulin receptor substrate-2 (IRS-2) have been implicated in phosphatidylinositol-3 (PI3) kinase activation downstream of IL-4Rα.
- Previous studies showed FES association in T cells and IRS-2 association in other cell types.
Purpose of the Study:
- To investigate whether Interleukin-4 (IL-4) activates both the FES-related and IRS-2 pathways to engage phosphatidylinositol-3 (PI3) kinase within the same cell.
- To analyze the tyrosine phosphorylation of IRS-2 and its association with PI3 kinase in response to IL-4.
- To identify the specific region of the IL-4Rα cytoplasmic domain responsible for IRS-2 tyrosine phosphorylation.
Main Methods:
- Utilized mouse pro-B (Ba/F3) and mast (MC9) cell lines.
- Analyzed protein-protein interactions using co-immunoprecipitation.
- Assessed protein tyrosine phosphorylation via Western blotting.
- Performed domain mapping of the IL-4Rα cytoplasmic tail.
Main Results:
- IL-4 stimulation induced tyrosine phosphorylation of IRS-2 in both Ba/F3 and MC9 cells.
- IL-4 also promoted the association of PI3 kinase with IRS-2 in these cell lines.
- Both FES or a FES-related protein and IRS-2 were found to associate with IL-4Rα and PI3 kinase simultaneously.
- A critical region within the IL-4Rα cytoplasmic domain was identified as essential for IRS-2 tyrosine phosphorylation.
Conclusions:
- IL-4 activates two distinct PI3 kinase signaling pathways within the same immune cells.
- These pathways involve both FES and IRS-2, highlighting a complex signaling network downstream of IL-4Rα.
- The findings provide insights into the molecular mechanisms regulating IL-4-mediated cellular responses.