Cytokine-specific transcriptional regulation through an IL-5R alpha interacting protein

Cytokine receptors consist of multiple subunits, which are often shared bet ween different receptors, resulting in the functional redundancy sometimes observed between cytokines. The interleukin 5 (IL-5) receptor consists of a n IL-5-specific alpha -subunit (IL-5R alpha) and a signal-transducing beta -subunit (betac) shared with the IL-3 and granulocyte-macrophage colony-sti mulating factor (GM-CSF) receptors. In this study, we sought to find a rote for the cytoplasmic domain of IL-5R alpha. We show that syntenin, a protei n containing PSD-95/Discs large/zO-1 (PDZ) domains, associates with the cyt oplasmic tail of the IL-5R alpha. Syntenin was found to directly associate with the transcription factor Sox4. Association of syntenin with IL-5R alph a was required for IL-5-mediated activation of Sox4. These studies identify a mechanism of transcriptional activation by cytokine-specific receptor su bunits.