Cytokine-Specific Transcriptional Regulation Through an IL-5Rα Interacting Protein

Abstract

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

Syntenin-mediated regulation of Sox4 proteasomal degradation modulates transcriptional output

“…We have previously reported that the adapter protein syntenin, also known as MDA-9, associates with Sox4 (Lin et al, 1998;Geijsen et al, 2001). Endogenous syntenin and Sox4 expression levels appear to correlate to some degree, particularly upon Mg132 treatment (Figure 1d).…”

“…We have previously shown that interleukin-5 signaling activates Sox4 transcriptional activity by syntenin associating with the IL5Ra-chain, and further demonstrated syntenin to modulate interleukin-5-induced eosinophil differentiation of hematopoietic stem cells (Geijsen et al, 2001;Beekman et al, 2009). In the current study, we have shown that syntenin can directly stabilize Sox4 expression in a variety of (interleukin-5R negative) tumor cell lines.…”

“…Reduced syntenin expression resulted in a 50% reduction in Sox4 protein expression, whereas mRNA levels for Sox4 remained unaffected (Figure 6a and Supplementary Figure S6). To study the capacity of syntenin to modulate endogenous Sox4 transcriptional activity, we utilized a luciferase reporter construct containing a Sox4 responsive promoter (Geijsen et al, 2001). We observed high promoter activity in HEK293 cells upon cotransfection of the reporter construct with wild-type Sox4, demonstrating Sox4 specificity (Figure 6b).…”

“…Expression of Sox4 299-440 was also enhanced by co-expression of syntenin. We have previously reported that the N-terminal domain of syntenin associates with Sox4 (Geijsen et al, 2001), and therefore investigated the syntenin-binding region within Sox4 by co-immunoprecipitation analysis. Sox4 and syntenin were found to co-immunoprecipitate, and both the Sox4 DBD (residues 59-135) and the C-terminal residues 299-440 were found to mediate association with syntenin ( Figure 4d).…”

“…The optimal Sox4 luciferase reporter construct was kindly provided by Dr H Clevers (Hubrecht Institute, Utrecht, The Netherlands). Syntenin constructs have been described (Geijsen et al, 2001). Poly-L-lysine, Mg132, epoxymycin, CHX and leptomycin B were from Sigma Aldrich.…”