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Key Event Title
Blockade of STAT5 phosphorylation
|Level of Biological Organization|
Key Event Components
|protein dephosphorylation||signal transducer and transcription activator STAT||decreased|
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP||Point of Contact||Author Status||OECD Status|
|Immune dysfunction induced by JAK3 inhibition||KeyEvent||Yasuhiro Yoshida (send email)||Under development: Not open for comment. Do not cite||Under Development|
|All life stages||High|
Key Event Description
The STAT family of proteins regulate gene transcription upon activation. The proteins rely on cytokine signaling and a number of growth factors through the JAK/STAT pathway (Kisseleva, et al. 2002). STAT activation is regulated by phosphorylation of protein monomers at conserved tyrosine residues, followed by binding to phospho-peptide pockets and subsequent dimerization (Gianti and Zauhar 2015). STAT5 has been implicated in cell growth and differentiation. 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 (Wakao, et al. 1992, Xu, et al. 1996).Thus, STAT5 proteins function as signal transduction molecules in the cytoplasm and as transcription factors upon translocation to the nucleus.
How It Is Measured or Detected
Phosphorylation of STAT5 tyrosine can be detected by specific antibodies using several detection systems, including flow cytometry. In one study, phosphorylated STAT5 expression was measured in T lymphocytes, and MFIs were reported for each subset (Osinalde, et al. 2017). A cell-permeable non-peptidic nicotinoyl hydrazone compound selectively targets the SH2 domain of STAT5 (IC50 = 47 µM against STAT5b SH2 domain EPO peptide binding activity), with markedly less recognition of the SH2 domain of STAT1, STAT3, or Lck (IC50 >500 µM). The compound was reported to block STAT5/STAT5 DNA binding activity in K562 nuclear extract and inhibit IFN-α-stimulated STAT5 tyrosine phosphorylation in Daudi cells, with no effect on STAT1 or STAT3 (Muller, et al. 2008).
Tyrosine phosphorylation of STAT5 induced by IL-2 has been analyzed using an anti-STAT5 antibody. In the study, this antibody immunoprecipitated STAT5 (p94 kDa). Peripheral blood lymphocytes were untreated (control) or treated with IL-2, IL-4, or IL-15 for 15 min. The extracts were incubated with biotinylated oligonucleotide bound to streptavidin-coated agarose. The agarose beads were washed and the eluted protein was immunoblotted with an antibody to STAT5 (Stahl, et al. 1994).
Other authors described the inhibition of JAK3 kinase activity by PF-06651600, 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 (Telliez, et al. 2016).
Pimozide is a specific inhibitor of STAT5 phosphorylation. Pimozide decreased the survival of chronic myelogenous leukemia cells resistant to kinase inhibitors (Nelson, et al. 2011). IL-2 markedly stimulated STAT5 phosphorylation in PBMCs from patients with chronic kidney disease (CKD). Pretreatment with pimozide (3 µM) 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 (Thibault, et al. 2016).
Gianti E, Zauhar RJ. 2015. An SH2 domain model of STAT5 in complex with phospho-peptides define "STAT5 Binding Signatures". J Comput Aided Mol Des 29:451-470. DOI: 10.1007/s10822-015-9835-6.
Kisseleva T, Bhattacharya S, Braunstein J, Schindler CW. 2002. Signaling through the JAK/STAT pathway, recent advances and future challenges. Gene 285:1-24.
Muller J, Sperl B, Reindl W, Kiessling A, Berg T. 2008. Discovery of chromone-based inhibitors of the transcription factor STAT5. Chembiochem 9:723-727. DOI: 10.1002/cbic.200700701.
Nelson EA, Walker SR, Weisberg E, Bar-Natan M, Barrett R, Gashin LB, Terrell S, Klitgaard JL, Santo L, Addorio MR, Ebert BL, Griffin JD, Frank DA. 2011. The STAT5 inhibitor pimozide decreases survival of chronic myelogenous leukemia cells resistant to kinase inhibitors. Blood 117:3421-3429. DOI: 10.1182/blood-2009-11-255232
Osinalde N, Sanchez-Quiles V, Blagoev B, Kratchmarova I. 2017. Data on interleukin (IL)-2- and IL-15-dependent changes in IL-2Rbeta and IL-2Rgamma complexes. Data Brief 11:499-506. DOI: 10.1016/j.dib.2017.02.030.
Stahl N, Boulton TG, Farruggella T, Ip NY, Davis S, Witthuhn BA, Quelle FW, Silvennoinen O, Barbieri G, Pellegrini S, et al. 1994. Association and activation of Jak-Tyk kinases by CNTF-LIF-OSM-IL-6 beta receptor components. Science 263:92-95.
Telliez JB, Dowty ME, 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 ME, Vincent F, Unwalla R, Liang S, Gilbert AM, Brown MF, Hayward M, Montgomery J, Yang X, Bauman J, Trujillo JI, Casimiro-Garcia A, Vajdos FF, Leung L, Geoghegan KF, Quazi A, Xuan D, Jones L, Hett E, Wright K, Clark JD, 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. DOI: 10.1021/acschembio.6b00677.
Thibault G, Paintaud G, Legendre C, Merville P, Coulon M, Chasseuil E, Ternant D, Rostaing L, Durrbach A, Di Giambattista F, Buchler M, 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. Transpl Int 29:184-195. DOI: 10.1111/tri.12688.
Wakao H, Schmitt-Ney M, 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.
Xu BC, Wang X, Darus CJ, Kopchick JJ. 1996. Growth hormone promotes the association of transcription factor STAT5 with the growth hormone receptor. J Biol Chem 271:19768-19773.