Event: 1716

Key Event Title


Blockade of STAT5 phosphorylation

Short name


STAT5 inhibition

Biological Context


Level of Biological Organization

Cell term


Cell term
T cell

Organ term


Organ term
immune system

Key Event Components


Process Object Action
protein dephosphorylation signal transducer and transcription activator STAT decreased

Key Event Overview

AOPs Including This Key Event


AOP Name Role of event in AOP
Immune dysfunction induced by JAK3 inhibition KeyEvent



Taxonomic Applicability


Term Scientific Term Evidence Link
Homo sapiens Homo sapiens High NCBI
Mus musculus Mus musculus High NCBI

Life Stages


Life stage Evidence
All life stages High

Sex Applicability


Term Evidence
Unspecific High

Key Event Description


Signal transducer and activator of transcription (STAT) is a family of proteins that regulate gene transcription upon activation, operated by cytokine signaling and a number of growth factors through the Janus-Associated-Kinase (JAK)/STAT  pathway (47-Kisseleva-2002). The STAT5 is a member of the STAT family of proteins, implicated in cell growth and differentiation. STAT activation is regulated by phosphorylation of protein monomers at conserved tyrosine residues, followed by binding to phospho-peptide pockets and subsequent dimerization (42-Gianti-2015). STAT5 was originally purified and cloned from mammary epithelial cells in sheep and identified as a signal transducer that confers the specific biological responses of prolactin (20-Wakao-1992,43-Xu-1996).Thus, STAT5 proteins play a double role as signal transduction molecules in the cytoplasm and as transcription factors upon translocation to the nuclear compartment.

How It Is Measured or Detected


Phosphorylation of tyrosine of STAT5 was detected by specific antibodies using several detection systems, including a flow cytometer. Phosphprylated-STAT5 expression was measured in T lymphocytes, and MFIs were reported for each subset (48-Osinalde-2017). A cell-permeable nonpeptidic nicotinoyl hydrazone compound that selectively targets the SH2 domain of STAT5 (IC50 = 47 µM against STAT5b SH2 domain EPO peptide binding activity), while exhibiting much less effect towards the SH2 domain of STAT1, STAT3, or Lck (IC50 >500 µM). Shown to block STAT5/STAT5 DNA binding activity in K562 nuclear extract and inhibit IFN-α-stimulated STAT5, but not STAT1 or STAT3, tyrosine phosphorylation in Daudi cells (49-Muller-2008).

Tyrosine phosphorylation of STAT5 induced by IL-2 can be analyzed with an anti-STAT5 antibody. This antibody immunoprecipitates STAT5 (p94 kDa). Peripheral blood lymphocytes were untreated (control) or treated with IL-2, IL-4, or IL-15 for 15 min, and extracts were incubated with biotinylated GRR oligonucleotide bound to streptavidin-coated agarose. The agarose beads were then washed, and the eluted protein was immunoblotted with antibody to STAT5 (40-Stahl-1994).

JAK3 selective inhibitor PF-06651600 can also inhibit the JAK3 kinase activity followed by inhibition of the phosphorylation of STAT5 elicited by IL-2, IL-4, IL-7, and IL-15 with IC50 values of 244, 340, 407, and 266 nM, respectively (7-Telliez-2016).

IL-2 remarkably stimulated STAT5 phosphorylation in peripheral blood mononuclear cells (PBMCs) from Chronic kidney disease (CKD) patients. Pimozide is a specific inhibitor of STAT5 phosphorylation.

Pimozide (3 µM) pretreatment dramatically suppressed IL-2-induced STAT5 phosphorylation, indicating that it is a potent blocker of IL-2-stimulated STAT5 phosphorylation in PBMCs from CKD patients.

Domain of Applicability


STAT5 is expressed in hematopoietic cells including T cells and B cells from humans, rodents and other mammalian species (50-Thibault-2016).

Evidence for Perturbation by Stressor



7.        Telliez, J. B., Dowty, M. E., Wang, L., Jussif, J., Lin, T., Li, L., Moy, E., Balbo, P., Li, W., Zhao, Y., Crouse, K., Dickinson, C., Symanowicz, P., Hegen, M., Banker, M. E., Vincent, F., Unwalla, R., Liang, S., Gilbert, A. M., Brown, M. F., Hayward, M., Montgomery, J., Yang, X., Bauman, J., Trujillo, J. I., Casimiro-Garcia, A., Vajdos, F. F., Leung, L., Geoghegan, K. F., Quazi, A., Xuan, D., Jones, L., Hett, E., Wright, K., Clark, J. D., and Thorarensen, A. (2016) Discovery of a JAK3-Selective Inhibitor: Functional Differentiation of JAK3-Selective Inhibition over pan-JAK or JAK1-Selective Inhibition. ACS Chem Biol 11, 3442-3451

20.      Wakao, H., Schmitt-Ney, M., and Groner, B. (1992) Mammary gland-specific nuclear factor is present in lactating rodent and bovine mammary tissue and composed of a single polypeptide of 89 kDa. J Biol Chem 267, 16365-16370

40.      Stahl, N., Boulton, T. G., Farruggella, T., Ip, N. Y., Davis, S., Witthuhn, B. A., Quelle, F. W., Silvennoinen, O., Barbieri, G., Pellegrini, S., and et al. (1994) Association and activation of Jak-Tyk kinases by CNTF-LIF-OSM-IL-6 beta receptor components. Science 263, 92-95

42.      Gianti, E., and Zauhar, R. J. (2015) An SH2 domain model of STAT5 in complex with phospho-peptides define "STAT5 Binding Signatures". J Comput Aided Mol Des 29, 451-470

43.      Xu, B. C., Wang, X., Darus, C. J., and Kopchick, J. J. (1996) Growth hormone promotes the association of transcription factor STAT5 with the growth hormone receptor. J Biol Chem 271, 19768-19773

47.      Kisseleva, T., Bhattacharya, S., Braunstein, J., and Schindler, C. W. (2002) Signaling through the JAK/STAT pathway, recent advances and future challenges. Gene 285, 1-24

48.      Osinalde, N., Sanchez-Quiles, V., Blagoev, B., and Kratchmarova, I. (2017) Data on interleukin (IL)-2- and IL-15-dependent changes in IL-2Rbeta and IL-2Rgamma complexes. Data in brief 11, 499-506

49.      Muller, J., Sperl, B., Reindl, W., Kiessling, A., and Berg, T. (2008) Discovery of chromone-based inhibitors of the transcription factor STAT5. Chembiochem : a European journal of chemical biology 9, 723-727

50.      Thibault, G., Paintaud, G., Legendre, C., Merville, P., Coulon, M., Chasseuil, E., Ternant, D., Rostaing, L., Durrbach, A., Di Giambattista, F., Buchler, M., and Lebranchu, Y. (2016) CD25 blockade in kidney transplant patients randomized to standard-dose or high-dose basiliximab with cyclosporine, or high-dose basiliximab in a calcineurin inhibitor-free regimen. Transplant international : official journal of the European Society for Organ Transplantation 29, 184-195