IL-6 activates STAT5 in T cells
Highlights
► IL-6 induces STAT5 phosphorylation in CD4 T cells. ► IL-6 up-regulates the STAT5-regulated CIS mRNA level in CD4 T cells. ► “Inflammatory” IL-6 levels are required to induce STAT5 activation.
Introduction
IL-6 is a cytokine extensively characterized for its role in the maturation of B cells [1] and the induction of the acute phase response [2], [3]. This role has been illustrated in IL-6-deficient mice that have a markedly impaired response to infection and lack the liver-induced acute phase response to infection and trauma [4]. During acute inflammation, IL-6 has a unique function in driving the transition from the early, predominantly neutrophilic innate response to the mononuclear adaptive response [5]. Recently, IL-6 has also emerged as a signal promoting the development of pro-inflammatory CD4 T cell helper (Th), Th17 [6], [7], [8], [9], [10] and follicular T helper (Tfh) cells [11], [12] and as an inhibitory signal for the differentiation of Th1 [13] and CD4 T regulatory (Treg) cell subsets [6], [14]. Besides their important roles in host defense, Th17 cells have been associated with several autoimmune and inflammatory disorders such as rheumatic diseases, multiple sclerosis and inflammatory bowel diseases [7], [15]. Tregs are central to the maintenance of peripheral immune tolerance and deficiencies in this population lead to devastating autoimmunity in both mice and human [16], [17].
Inhibition of IL-6 is a promising therapeutic avenue which has been extensively investigated in preclinical models of inflammatory and auto-immune diseases [18], [19], [20]. This has led to the development of humanized and fully human antibodies (Abs) directed against both IL-6 [21] and IL-6Rα such as tocilizumab [22], [23]. This antibody has been tested in clinical trials for the treatment of Castelman’s disease [24], rheumatoid arthritis [25], [26], [27], juvenile idiopathic arthritis [28] and Crohn’s disease [29]. It has been approved by Japanese, European and US regulatory agencies [23], [30].
IL-6 signals through a receptor comprising the non-signaling IL-6Rα chain and gp130 [31]. This leads to the activation of several signaling pathways among which Janus kinase (JAK)/signal transducers and activators of transcription 3 (STAT3) is the most validated in the control of CD4 Th differentiation [32], [33], [34], [35] and in IL-6 mediated pathologies [31], [36], [37], [38], [39]. The IL-6 receptor α chain is shared by IL-6 and ciliary neurotrophic factor while gp130 is a common signaling component in other cytokine receptors such as IL-11, leukemia inhibitory factor, ciliary neurotrophic factor, cardiotrophin-1, oncostatin M, cardiotrophin-like cytokine, neuropoietin, IL-27 and IL-35 [31], [40], [41], [42].
Soluble forms of IL-6Rα have been found in various body fluids [20], [31]. They are generated by metalloproteinase cleavage of the membrane form of IL-6Rα or by the translation of an mRNA encoding a secreted IL-6Rα generated by alternative splicing [20], [43], [44]. These soluble forms bind IL-6 and activate cells expressing only gp130, a process known as trans-signaling [20], [31]. As expression of IL-6Rα is very restricted whereas the expression of gp130 is ubiquitous, IL-6 trans-signaling plays a crucial role in mediating IL-6 functions during inflammation [20], [31], [45].
The IL-6-mediated induction of Th17 and Tfh differentiation can be inhibited by IL-2 via STAT5 [46], [47]. STAT5 is believed to compete with STAT3 and to repress STAT3 target promoters [48], [49]. Surprisingly, we observed that IL-6 induces STAT5 activation in mouse T cells in vitro. In CD4 T cells this was paralleled by the up-regulation of cytokine-inducible SH2-containing protein (CIS) mRNA which is encoded by a gene regulated by STAT5. These results suggest an unexpected level of complexity in the activation of the STAT signaling pathways activated by IL-6 in CD4 T cells.
Section snippets
Experimental animals
All procedures conformed to the Canadian Council on Animal Care guidelines and were approved by the Animal Ethics Committee of the Université de Montréal. Six- to eight-week-old female C57BL/6 mice were purchased from Jackson Laboratory, Bar Harbor, ME.
Expression and isolation of recombinant proteins
The construct for the expression of mouse hyper-IL-6 was described previously [50]. Recombinant proteins were expressed and purified under conditions ensuring the absence of endotoxin contamination [50] and quantified by Western blot analysis
IL-6 induces STAT5 phosphorylation in resting T cells
IL-6 is known to induce STAT1 and STAT3 phosphorylation in IL-6Rα expressing immune cells [31], [54]. Unexpectedly, we observed that this cytokine can also induce STAT5 phosphorylation in a fraction of mouse spleen mononuclear cells (Fig. 1A). Hyper-IL-6, a soluble IL-6Rα-IL6 fusion protein, can be used to induce IL-6 trans-signaling, which is mediated by soluble IL-6Rα-IL6 complexes binding and activating cells expressing only gp130 [20], [31], [54]. STAT5 phosphorylation was induced in a
Discussion
We observed that incubation of resting or activated CD4 T cells with IL-6 induces the phosphorylation of STAT5. Since STAT5 activation by IL-2 is believed to be a key signaling event for constraining the role of IL-6 in Tfh and Th17 differentiation, our observation was unexpected [46], [47], [48], [49], [56]. IL-6 induced the up-regulation of CIS mRNA, a gene which is known to be regulated by STAT5 [62], [63], [64], indicating that STAT5 phosphorylation results in the functional activation of
Acknowledgments
We thank S. Sénechal (Université de Montréal, Montreal, Canada) for help with flow cytometry and the IRIC genomic platform (Université de Montréal, Montreal, Canada) for the real time PCR assays. This work was supported by the Canadian Institutes of Health Research (MOP-57832).
References (86)
- et al.
Recombinant human B cell stimulatory factor 2 (BSF-2/IFN-beta 2) regulates beta-fibrinogen and albumin mRNA levels in Fao-9 cells
FEBS Lett
(1987) - et al.
Il-6 and its soluble receptor orchestrate a temporal switch in the pattern of leukocyte recruitment seen during acute inflammation
Immunity
(2001) - et al.
TGFbeta in the context of an inflammatory cytokine milieu supports de novo differentiation of IL-17-producing T cells
Immunity
(2006) - et al.
Generation of T follicular helper cells is mediated by interleukin-21 but independent of T helper 1, 2, or 17 cell lineages
Immunity
(2008) - et al.
Inhibition of Th1 differentiation by IL-6 is mediated by SOCS1
Immunity
(2000) - et al.
The wolf in sheep’s clothing: the role of interleukin-6 in immunity, inflammation and cancer
Trend Mol Med
(2008) - et al.
IL-6 in autoimmune disease and chronic inflammatory proliferative disease
Cytokine Growth Factor Rev
(2002) - et al.
Humanized anti-interleukin-6 receptor antibody treatment of multicentric Castleman disease
Blood
(2005) - et al.
Effect of interleukin-6 receptor inhibition with tocilizumab in patients with rheumatoid arthritis (OPTION study): a double-blind, placebo-controlled, randomised trial
Lancet
(2008) - et al.
Efficacy and safety of tocilizumab in patients with systemic-onset juvenile idiopathic arthritis: a randomised, double-blind, placebo-controlled, withdrawal phase III trial
Lancet
(2008)
A pilot randomized trial of a human anti-interleukin-6 receptor monoclonal antibody in active Crohn’s disease
Gastroenterology
STAT3 regulates cytokine-mediated generation of inflammatory helper T cells
J Biol Chem
IL-6 and Stat3 are required for survival of intestinal epithelial cells and development of colitis-associated cancer
Cancer Cell
Gp130-mediated Stat3 activation in enterocytes regulates cell survival and cell-cycle progression during colitis-associated tumorigenesis
Cancer Cell
Signaling of human ciliary neurotrophic factor (CNTF) revisited. The interleukin-6 receptor can serve as an alpha-receptor for CTNF
J Biol Chem
Isolation of an mRNA encoding a soluble form of the human interleukin-6 receptor
Cytokine
Cellular cholesterol depletion triggers shedding of the human interleukin-6 receptor by ADAM10 and ADAM17 (TACE)
J Biol Chem
Interleukin-2 signaling via STAT5 constrains T helper 17 cell generation
Immunity
New insights into the roles of Stat5a/b and Stat3 in T cell development and differentiation
Semin Cell Dev Biol
Preparation of cDNA and the generation of cDNA libraries: overview
Methods Enzymol
Increased plasma levels of interleukin-6 in sepsis
Blood
Serum cytokine levels in human septic shock. Relation to multiple-system organ failure and mortality
Chest
Multiple reasons for an inefficient STAT1 response upon IL-6-type cytokine stimulation
Cell Signal
STAT5A-deficient mice demonstrate a defect in granulocyte-macrophage colony-stimulating factor-induced proliferation and gene expression
Blood
CIS, a cytokine inducible SH2 protein, is a target of the JAK-STAT5 pathway and modulates STAT5 activation
Blood
The role of shared receptor motifs and common Stat proteins in the generation of cytokine pleiotropy and redundancy by IL-2, IL-4, IL-7, IL-13, and IL-15
Immunity
IL-27, a heterodimeric cytokine composed of EBI3 and p28 protein, induces proliferation of naive CD4(+) T cells
Immunity
Pathogenic significance of interleukin-6 (IL-6/BSF-2) in Castleman’s disease
Blood
An indirect effect of Stat5a in IL-2-induced proliferation: a critical role for Stat5a in IL-2-mediated IL-2 receptor alpha chain induction
Immunity
Nonredundant roles for Stat5a/b in directly regulating Foxp3
Blood
T cell-produced transforming growth factor-beta1 controls T cell tolerance and regulates Th1- and Th17-cell differentiation
Immunity
TGF-beta suppresses tumor progression in colon cancer by inhibition of IL-6 trans-signaling
Immunity
STAT3 and STAT5B are targets of two different signal pathways activated by hematopoietin receptors and control transcription via separate cytokine response elements
J Biol Chem
Transcription factors Stat3 and Stat5b are present in rat liver nuclei late in an acute phase response and bind interleukin-6 response elements
J Biol Chem
Complementary DNA for a novel human interleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin
Nature
Interferon beta 2/B-cell stimulatory factor type 2 shares identity with monocyte-derived hepatocyte-stimulating factor and regulates the major acute phase protein response in liver cells
Proc Natl Acad Sci USA
Impaired immune and acute-phase responses in interleukin-6-deficient mice
Nature
Reciprocal developmental pathways for the generation of pathogenic effector TH17 and regulatory T cells
Nature
T(H)-17 cells in the circle of immunity and autoimmunity
Nat Immunol
TGF-beta and IL-6 drive the production of IL-17 and IL-10 by T cells and restrain T(H)-17 cell-mediated pathology
Nat Immunol
Transforming growth factor-beta induces development of the T(H)17 lineage
Nature
IL-21 and IL-6 are critical for different aspects of B cell immunity and redundantly induce optimal follicular helper CD4 T cell (Tfh) differentiation
PLoS One
Toll pathway-dependent blockade of CD4 + CD25 + T cell-mediated suppression by dendritic cells
Science
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