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Relationship: 2024


A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Inhibition of JAK3 leads to STAT5 inhibition

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Inhibition of JAK3 leading to impairment of T-Cell Dependent Antibody Response adjacent High High Yasuhiro Yoshida (send email) Under development: Not open for comment. Do not cite Under Development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help
Term Scientific Term Evidence Link
Homo sapiens Homo sapiens High NCBI
Mus musculus Mus musculus High NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Unspecific High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
All life stages High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Nelson et al. reported that a membrane proximal region of the interleukin-2 receptor gamma c chain sufficient for Jak kinase activation and induction of proliferation in T cells (Nelson, et al. 1996). Furthermore, Kirken RA et al. demonstrated that activation of JAK3, but not JAK1, is critical for IL-2-induced proliferation and STAT5 recruitment by a COOH-terminal region of the IL-2 receptor beta-chain (Kirken, et al. 1995). Therefore, STAT activation is regulated by JAK via phosphorylation. Thus, JAK inhibitors commonly interfere with STAT activation.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

STAT5 refer to two proteins that share 94% structural homology and are transcribed from separate genes, STAT5A and STAT5B. Binding of these extracellular ligands to their target receptors induces the activation of receptor-associated JAK kinases that phosphorylate key tyrosine residues within the receptor, providing docking sites for the SRC homology 2 (SH2) domains of the inactive cytoplasmic STAT5 monomers. STAT5 is then phosphorylated at specific tyrosine residues, either Y694 (STAT5A) or Y699 (STAT5B) of the C-terminus. Subsequently, STAT5 undergoes a conformational change and phosphorylated STAT5 monomers form either homo- or hetero- STAT5X-STATX dimers through reciprocal phosphotyrosine–SH2 interactions (Cumaraswamy, et al. 2014, Tothova, et al. 2021). This means that STAT5 will never be activated without this phosphorylation step by JAK3.

Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help

STAT5 plays a major role in regulating vital cellular functions, such as proliferation, differentiation, and apoptosis, of hematopoietic and immune cells (Wakao, et al. 1992). STAT5 is activated by JAK3 phosphorylation of a single tyrosine residue (Y694).

Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help
Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help


Dose-response analysis of the effects of RB1 on JAK3 kinase activity showed that RB1 inhibits JAK3 kinase activity in a dose-dependent manner with an IC50 value of 40 nM, without inhibiting JAK1, JAK2, or TYK2 (Pei, et al. 2018).

Normal rats were administered peficitinib at 10 and 20 mg/kg. Thirteen hours later, the animals were bled and STAT5 phosphorylation was assessed. IL-2-induced STAT5 phosphorylation of CD3-positive lymphocytes in peripheral blood from the peficitinib-treated rats was suppressed by 37% at a dose of 10 mg/kg and 78% at 20 mg/kg (Gianti and Zauhar 2015).

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

The enzymatic activities against JAK1, JAK2, JAK3, and TYK2 were immediately tested in CTLL-2 cells using a Caliper Mobility Shift Assay with an ATP concentration at Km (Pei, et al. 2018). CTLL-2 cells were treated with 10 µM adenosine (plus coformycin) for 15 min at 37°C and then stimulated with IL-2 (10 U/mL) for different lengths of time (5 min-12 h). Adenosine dramatically decreased dose-dependent STAT5A/B tyrosine phosphorylation in response to IL-2 over the entire 12 h time course (Zhang, et al. 2004).

Known Feedforward/Feedback loops influencing this KER
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help


List of the literature that was cited for this KER description. More help

Al-Shami A, Mahanna W, Naccache PH. 1998. Granulocyte-macrophage colony-stimulating factor-activated signaling pathways in human neutrophils. Selective activation of Jak2, Stat3, and Stat5b. J Biol Chem 273:1058-1063. DOI: 10.1074/jbc.273.2.1058.

Cumaraswamy AA, Lewis AM, Geletu M, Todic A, Diaz DB, Cheng XR, Brown CE, Laister RC, Muench D, Kerman K, Grimes HL, Minden MD, Gunning PT. 2014. Nanomolar-Potency Small Molecule Inhibitor of STAT5 Protein. ACS Med Chem Lett 5:1202-1206. DOI: 10.1021/ml500165r.

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.

Kirken RA, Rui H, Malabarba MG, Howard OM, Kawamura M, O'Shea JJ, Farrar WL. 1995. Activation of JAK3, but not JAK1, is critical for IL-2-induced proliferation and STAT5 recruitment by a COOH-terminal region of the IL-2 receptor beta-chain. Cytokine 7:689-700. DOI: S1043466685700816 [pii]


Nelson BH, Lord JD, Greenberg PD. 1996. A membrane-proximal region of the interleukin-2 receptor gamma c chain sufficient for Jak kinase activation and induction of proliferation in T cells. Mol Cell Biol 16:309-317. DOI: 10.1128/MCB.16.1.309.

Pei H, He L, Shao M, Yang Z, Ran Y, Li D, Zhou Y, Tang M, Wang T, Gong Y, Chen X, Yang S, Xiang M, Chen L. 2018. Discovery of a highly selective JAK3 inhibitor for the treatment of rheumatoid arthritis. Sci Rep 8:5273. DOI: 10.1038/s41598-018-23569-y.

Tothova Z, Tomc J, Debeljak N, Solar P. 2021. STAT5 as a Key Protein of Erythropoietin Signalization. Int J Mol Sci 22. DOI: 7109 [pii]10.3390/ijms22137109ijms22137109 [pii].

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.

Zhang H, Conrad DM, Butler JJ, Zhao C, Blay J, Hoskin DW. 2004. Adenosine acts through A2 receptors to inhibit IL-2-induced tyrosine phosphorylation of STAT5 in T lymphocytes: role of cyclic adenosine 3',5'-monophosphate and phosphatases. J Immunol 173:932-944. DOI: 10.4049/jimmunol.173.2.932.