Characterization of phosphopeptide motifs specific for the Src homology 2 domains of signal transducer and activator of transcription 1 (STAT1) and STAT3.

Signal transducers and activators of transcription (STAT) 1 and STAT3 are activated by overlapping but distinct sets of cytokines. STATs are recruited to the different cytokine receptors through their Src homology (SH) 2 domains that make highly specific interactions with phosphotyrosine-docking sites on the receptors. We used a degenerate phosphopeptide library synthesized on 35-microm TentaGel beads and fluorescence-activated bead sorting to determine the sequence specificity of the peptide-binding sites of the SH2 domains of STAT1 and STAT3.

The interleukin-4/interleukin-13 receptor of human synovial fibroblasts: overexpression of the nonsignaling interleukin-13 receptor alpha2.

Interleukin (IL)-4 and IL-13 are known to bind to shared heteromultimeric receptor complexes of variable composition. Given the many regulatory effects of IL-4 and IL-13 on synovial cells, we aimed to characterize their IL-4/IL-13 receptor (R). Cultivated synovial fibroblasts expressed transcripts for IL-4Ralpha and IL-13Ralpha1, the human homolog of the recently cloned mouse IL-13R, but not the common gamma-chain of the IL-2R.