p-Stat5a Background Information Stat5 (Signal Transducers and Activators of Transcription 5) is important in regulating T cell functions involving the receptors for Interleukin-2 (IL-2) (1). IL-2 stimulates the rapid phosphorylation of both serine and tyrosine residues of Stat5a and Stat5b in human T lymphocytes and in several IL-2-responsive lymphocytic cell lines (2–4). IL-2 differentially induces serine phosphorylation of Stat5a and Stat5b on Ser726 and Ser731, respectively (2,5). Stat5b is preferentially phosphorylated and displays more protracted serine phosphorylation kinetics than Stat5a (2,5). Both the acid-rich region and the COOH terminus of IL-2Rb can independently mediate IL-2-induced Stat 5a/b serine phosphorylation, suggesting that Stat5a/b serine phosphorylation occurs at a postreceptor level (2). Stat5a is phosphorylated on Tyr694 in a prolactin-sensitive manner, whereas serine phosphorylation is constitutive. Activation of Stat5 by IL-2 may help govern the biological effects of IL-2 during the immune response (3). Ser779 is constitutively phosphorylated in the mammary gland, and Ser725 phosphorylation influences prolactin-stimulated in vitro DNA binding activity.
p-Stat5a (Ser 780)
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p-Stat5a (Ser 780): sc-101805. Immunoperoxidase staining of formalin-fixed, paraffin-embedded human breast carcinoma tissue showing nuclear staining.
Western blot analysis of phosphorylated Stat5a expression in HeLa whole cell lysates. Blots were probed with p-Stat5a (Ser 780): sc-101805 (A) and p-Stat5a (Ser 780): sc-101805 preincubated with cognate phosphorylated peptide (B).
