Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis.
Interleukin-9 ( IL-9) is a cytokine with pleiotropic effects on mast cell and T cell lines. It exerts its effects through the IL-9R complex consisting of IL-9Ralpha and the common gammac subunit. Here we report functional evidence for receptor heteromerization for efficient signal transduction, and we define minimal requirements in the two receptor subunits for IL-9R function. Tyrosine 336 of the IL-9Ralpha and the membrane-proximal segment of gammac are both crucial for signaling. The activated IL-9R complex employs the Janus kinases JAK1 and JAK3 for subsequent activation of the signal transducer and activator transcription (STAT) factors STAT-1, STAT-3, and STAT-5. This process is independent of Tyk2. We demonstrate further that the activated STAT complexes consist of STAT-1 and STAT-5 homodimers and STAT-1-STAT-3 heterodimers. Finally, we show that IL-9R signaling in a T cell line does not result in detectable mitogen-activated protein kinase activation and leads to unsustained proliferation. Nonetheless, these T cells are efficiently protected from dexamethasone-induced apoptosis. These results further define the molecular architecture of the IL-9R and its specific connections to various biologic responses.[1]References
- Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis. Bauer, J.H., Liu, K.D., You, Y., Lai, S.Y., Goldsmith, M.A. J. Biol. Chem. (1998) [Pubmed]
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