Biomedical subjects

Y Jacques

Publications and source records attributed to Y Jacques.

At least 19 recordsLinked to original sources

PubMed2006

Loss of oncostatin M receptor beta in metastatic melanoma cells.

Oncostatin M (OSM) is an interleukin-6 (IL-6) type cytokine originally described by its capacity to inhibit melanoma proliferation in vitro. Here, the mechanisms involved in resistance to growth inhibition by OSM were analysed for the first time on a large panel of metastatic melanoma cell lines. OSM resistance did not strictly correlate with IL-6, interferon-gamma or tumor necrosis factor-alpha resistance. Rather, it correlated with a specific loss of the OSM receptor-beta (OSMRbeta) subunit, in conjunction with a lower level of histone acetylation in the OSMRbeta promoter region. Treatment of various OSM-resistant melanoma cells with the histone deacetylase inhibitor Trichostatin A increased activity and histone acetylation of the OSMRbeta promoter as well as expression of OSMRbeta mRNA and protein, allowing OSM to activate the signal transducer and activator of transcription 3 (STAT3) and to inhibit proliferation. Other defects associated with OSM resistance were identified at the level of OSMRbeta transcription or protein expression, as well as downstream of or parallel to STAT3 activation. Altogether, our results suggest a role for OSM in the prevention of melanoma progression and that metastatic melanoma cells could escape this growth control by the epigenetic silencing of OSMRbeta.

Acetylation↗

PubMed2001

Identification of agonistic and antagonistic antibodies against gp190, the leukemia inhibitory factor receptor, reveals distinct roles for its two cytokine-binding domains.

The receptor for the cytokine leukemia inhibitory factor (LIF) associates the low affinity binding component gp190 and the high affinity converter gp130, both of which are members of the family of hematopoietic receptors characterized by the cytokine receptor homology (CRH) domain. The gp190 is among the very few members of this large family to contain two CRH domains. The membrane-distal one (herein called D1) is followed by an Ig-like domain, a membrane-proximal CRH domain called D2, and three type III fibronectin repeats. We raised a series of monoclonal antibodies specific for the human gp190. Among them was the blocking antibody 1C7, which was directed against the D1Ig region and which impaired the binding of LIF to gp190. Another blocking antibody, called 12D3, was directed against domain D2 and interfered with the reconstitution of the high affinity receptor complex, independently of the interaction between LIF and gp190. The blocking effect of these two antibodies concerned four cytokines known to use gp190, i.e. LIF, oncostatin M, ciliary neurotrophic factor, and cardiotrophin-1. Among 23 antibodies tested alone or in combination (two anti-D2 and 21 anti-D1Ig), only the mixture of the two anti-D2 antibodies displayed agonistic activity in the absence of the cytokine. Taken together, these results demonstrate that the two CRH domains of gp190 play different functions in ligand binding and receptor activation.

Animals↗

PubMed2001

Identification of the domain in the human interleukin-11 receptor that mediates ligand binding.

The interleukin-11 receptor (IL-11R) belongs to the hematopoietic receptor superfamily. The functional receptor complex comprises IL-11, IL-11R and the signal-transducing subunit gp130. The extracellular part of the IL-11R consists of three domains: an N-terminal immunoglobulin-like domain, D1, and two fibronectin-type III-like (FNIII) domains and D2 and D3. The two FNIII domains comprise the cytokine receptor-homology region defined by a set of four conserved cysteine residues in the N-terminal domain (D2) and a WSXWS sequence motif in the C-terminal domain (D3). We investigated the structural and functional role of the third extracellular receptor domain of IL-11R. A molecular model of the human IL-11/IL-11R complex allowed the identification of amino acid residues in IL-11R to be involved in ligand binding. Most of them were located in the third extracellular domain, which therefore should be able to bind with high affinity to IL-11. To prove this prediction, domain D3 of the IL-11R was expressed in Escherichia coli, refolded and purified. For structural characterization, circular dichroism, fluorescence and NMR spectroscopy were used. By plasmon resonance experiments, we show that the ligand-binding capacity of this domain is as high as that one for the whole receptor. These results provide a basis for further structural investigations that could be used for the rational design of potential agonists and antagonists essential in human therapy.

Amino Acid Sequence↗

PubMed2001

Negative cross-talk between interleukin-3 and interleukin-11 is mediated by suppressor of cytokine signalling-3 (SOCS-3).

Previous studies have shown that addition of interleukin-3 (IL-3) abrogated the B-cell potential of primary colonies supported by IL-11, erythropoietin, IL-7 and steel factor. However, the mechanism by which IL-3 exerts its inhibitory role is not understood. Using a variant of the mouse pro-B cell line Ba/F3 which expresses both IL-3 and IL-11 receptors, we showed that pretreatment of these cells with IL-3 before stimulation by IL-11 suppressed the tyrosine phosphorylation and nuclear translocation of STAT3 (signal transducer and activator of transcription 3). This inhibition occurred within 30 min and required the synthesis of a negative regulator. The onset of IL-3-dependent inhibition was correlated temporally with the appearance of SOCS-3 (suppressor of cytokine signalling-3) protein. In addition, overexpression of SOCS-3 in the pro-B cell line effectively blocked STAT3 activation induced by IL-11. These findings establish that a cytokine (IL-3) that has been shown to modulate its own signal of activation is also able to down-regulate signalling activated by a different cytokine (IL-11). This cross-talk involves activation of the JAK (Janus kinase)/STAT signalling pathway, but not mitogen-activated protein kinase pathways, and is mediated, at least in part, by SOCS-3.

Animals↗

PubMed2001

Factors and strategies for improving buccal absorption of peptides.

Peptides and polypeptides have important pharmacological properties but only a limited number (e.g. insulin, oxytocin, vasopressin) have been exploited as therapeutics because of problems related to their delivery. The buccal mucosa offers an alternative route to conventional, parenteral administration. Peptides are generally not well absorbed through mucosae because of their molecular size, hydrophilicity and the low permeability of the membrane. Peptide transport across buccal mucosa occurs via passive diffusion and is often accompanied by varying degrees of metabolism. This review describes various approaches to improve the buccal absorption of peptides including the use of penetration enhancers to increase membrane permeability and/or the addition of enzyme inhibitors to increase their stability. Other strategies including molecular modification with bioreversible chemical groups or specific formulations such as bioadhesive delivery systems are also discussed.

Administration, Buccal↗

PubMed2001

Interleukin-15 expression in cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome).

BACKGROUND: Cytokines are of potential importance in the pathogenesis of cutaneous T-cell mediated disorders, including cutaneous T-cell lymphoma (CTCL). OBJECTIVES: To compare interleukin (IL)-15 expression in certain inflammatory cutaneous diseases, with that in CTCL (mycosis fungoides and Sézary syndrome). METHODS: IL-15 mRNA and protein expression were examined by in situ hybridization and immunohistochemistry, respectively, on formalin-fixed, paraffin-embedded biopsies of normal human skin, atopic dermatitis, psoriasis, parapsoriasis and CTCL. RESULTS: Despite similar expression of IL-15 mRNA, we found differences in IL-15 protein expression between normal human skin, atopic dermatitis and psoriasis on the one hand, and parapsoriasis and CTCL on the other. IL-15 protein expression was not detected in normal human skin, atopic dermatitis or psoriasis, but was detected, mainly at low levels but in a few patients at higher levels, in epidermal keratinocytes in parapsoriasis, mycosis fungoides and Sézary syndrome. CONCLUSIONS: Induction of keratinocyte IL-15 expression appears to be a feature of CTCL. The factors stimulating such an expression remain unknown.

Antineoplastic Agents↗

PubMed2001

Characterization of an IL-2 mimetic with therapeutic potential.

Human interleukin-2 (IL-2) interacts with two types of functional receptors (IL-2R alpha betagamma and IL-2R betagamma) and acts on a broad range of target cells involved in inflammatory reactions and immune responses. IL-2 is also used in different clinical trials aimed at improving the treatment of some cancers and the recovery of CD4 lymphocytes by HIV patients. The therapeutic index of IL-2 is limited by various side effects dominated by the vascular leak syndrome. We have shown that a chemically synthesised fragment of the IL-2 sequence can fold into a helical tetramer likely mimicking the quatemary structure of an hemopoietin. Indeed, peptide p1-30 (containing amino acids 1 to 30, including the sequence corresponding to the entire alpha helix A of IL-2) spontaneously folds into an alpha-helical homotetramer and stimulates the growth of T-cell lines expressing human IL-2R beta, whereas shorter versions of the peptide lack helical structure and are inactive. At the cellular level, p1-30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8 low lymphocytes and natural killer cells, which constitutively express IL-2R beta. A significant IFN-gamma production is also detected following p1-30 stimulation. A mutant form of p1-30 (Asp20-->Lys) which is likely unable to induce vascular leak syndrome remains capable to generate LAK cells like the original p1-30 peptide. Altogether our data suggest that p1-30 has therapeutic potential.

CD8-Positive T-Lymphocytes↗

PubMed2000

Stimulation of leukemia inhibitory factor receptor degradation by extracellular signal-regulated kinase.

Leukemia inhibitory factor (LIF) signals via the heterodimeric receptor complex comprising the LIF receptor alpha subunit (LIFRalpha) and the common signal transducing subunit for interleukin-6 cytokine receptors, gp130. This study demonstrates that in different cell types, the level of LIFRalpha decreases during treatment with LIF or the closely related cytokine oncostatin M (OSM). Moreover, insulin and epidermal growth factor induce a similar LIFRalpha down-regulation. The regulated loss of LIFRalpha is specific since neither gp130 nor OSM receptor beta shows a comparable change in turnover. LIFRalpha down-regulation correlates with reduced cell responsiveness to LIF. Using protein kinase inhibitors and point mutations in LIFRalpha, we demonstrate that LIFRalpha down-regulation depends on activation of extracellular signal-regulated kinase 1/2 and phosphorylation of the cytoplasmic domain of LIFRalpha at serine 185. This modification appears to promote the endosomal/lysosomal pathway of the LIFRalpha. These results suggest that extracellular signal-regulated kinase-activating factors like OSM and growth factors have the potential to lower specifically LIF responsiveness in vivo by regulating LIFRalpha half-life.

3T3 Cells↗

PubMed2000

Monoclonal antibodies against the human interleukin-11 receptor alpha-chain (IL-11Ralpha) and their use in studies of human mononuclear cells.

A panel of 14 hybridoma cell lines secreting monoclonal antibodies against the human interleukin-11 receptor alpha chain (hIL-11Ralpha) was obtained using two different approaches. Two antibodies were raised against peptides of the N- and C-terminal sequences, respectively, of the extracellular part of the hIL-11Ralpha. Another group of 12 antibodies was generated against a hybrid protein consisting of the extracellular part of the hIL-11Ralpha fused to mature full-length human IL-2. All these antibodies recognized native hIL-11Ralpha and most also recognized the denatured receptor on immunoblots after SDS-PAGE. Four different epitopes were identified on the extracellular part of the hIL-11Ralpha. One epitope, defined by the E27 antibody, is located at the N-terminus and the other three epitopes are clustered in the membrane-proximal, C-terminal region. The antibodies defining epitopes I and II recognized membrane-bound hIL-11Ralpha expressed in gp130/hIL-11Ralpha-co-transfected Ba/F3 cells. The E27 antibody cross-reacted with murine IL-11Ralpha, in agreement with the fact that the N-terminal region is highly conserved between species. The other 13 antibodies all recognized a region between amino acids 319 and 363, which is the membrane-proximal part of the hIL-11Ralpha. This region, which is less conserved between mouse and human, is shown here to be an immunodominant region. Anti-IL-11Ralpha monoclonal antibodies, which have not been described previously enabled us to explore the expression and tissue distribution of IL-11Ralpha on human peripheral blood mononuclear cells and cell lines. The antibodies provide powerful tools for the study of the regulation and function of the receptor.

Amino Acid Sequence↗

PubMed2000

The first alpha helix of interleukin (IL)-2 folds as a homotetramer, acts as an agonist of the IL-2 receptor beta chain, and induces lymphokine-activated killer cells.

Interleukin (IL)-2 interacts with two types of functional receptors (IL-2Ralphabetagamma and IL-2Rbetagamma) and acts on a broad range of target cells involved in inflammatory reactions and immune responses. For the first time, we show that a chemically synthesized fragment of the IL-2 sequence can fold into a molecule mimicking the quaternary structure of a hemopoietin. Indeed, peptide p1-30 (containing amino acids 1-30, covering the entire alpha helix A of IL-2) spontaneously folds into an alpha-helical homotetramer and stimulates the growth of T cell lines expressing human IL-2Rbeta, whereas shorter versions of the peptide lack helical structure and are inactive. We also demonstrate that this neocytokine interacts with a previously undescribed dimeric form of IL-2Rbeta. In agreement with its binding to IL-2Rbeta, p1-30 activates Shc and p56(lck) but unlike IL-2, fails to activate Janus kinase (Jak)1, Jak3, and signal transducer and activator of transcription 5 (STAT5). Unexpectedly, we also show that p1-30 activates Tyk2, thus suggesting that IL-2Rbeta may bind to different Jaks depending on its oligomerization. At the cellular level, p1-30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8(low) lymphocytes and natural killer cells, which constitutively express IL-2Rbeta. A significant interferon gamma production is also detected after p1-30 stimulation. A mutant form of p1-30 (Asp20-->Lys), which is likely unable to induce vascular leak syndrome, remains capable of generating LAK cells, like the original p1-30 peptide. Altogether, our data suggest that p1-30 has therapeutic potential.

Amino Acid Sequence↗

PubMed2000

Positive regulation of human T cell activation by Gi2 proteins and interleukin-8.

We investigated whether pertussis toxin (PT)-sensitive heterotrimeric Gi proteins (Gi1, Gi2, Gi3) are involved in the regulation of TCR-induced activation of human T cells. First, Gi proteins were inactivated by PT: pretreatment with PT of purified blood T lymphocytes before CD3 cross-linking inhibited cell proliferation (-71.1 +/- 22.0%, P < 0.001), production of interleukin-2 (IL-2; -47.3 +/- 12.6%, P = 0.008), and expression of CD25 (-24.6 +/- 11.7%, P < 0.001) and CD69 (-25.7 +/- 9.0%, P < 0.001). Then, to identify which of the three Gi was involved, Gi1, Gi2, and Gi3 proteins were specifically inactivated by stably transfecting dominant-negative mutated forms of their alpha subunit in Jurkat cells. After activation, IL-2 production and CD69 expression were inhibited only in cells expressing inactive Gi2. We then studied the effects of interleukin-8 (IL-8), a CXC-chemokine with receptors coupled to Gi2 and produced in an autocrine fashion by activated T cells. Although its effects varied among donors, exogenous IL-8 stimulated proliferation and CD25 expression (up to, respectively, 200 and 77%) of PB T lymphocytes in response to CD3 activation, in a PT-sensitive manner. IL-8 also stimulated IL-2 production (by up to 42%) and CD69 expression, although weakly (+27%). Anti-human IL-8 antibody inhibited proliferation (-43%) and CD25 up-regulation (-45%) of activated T lymphocytes. In summary, several major responses of human T lymphocytes to TCR-mediated activation are regulated by Gi2 proteins, which for this function can be activated by IL-8 in an autocrine manner.

Animals↗

PubMed2000

Cloning and expression of CIS6, chromosome assignment to 3p22 and 2p21 by in situ hybridization.

A family of negative regulators of JAK signaling pathway referred to as suppressor of cytokines signaling (SOCS) or cytokine-inducible SH2 protein (CIS) has been recently identified. In order to find additional members of this family, we have used a consensus amino acid sequence contained in the well-conserved central SH2 domain to search DNA databases. We isolated cDNA coding for the human homologue of SOCS-5, referred to as CIS6. Northern blot analysis revealed CIS6 mRNA expression in various tissues such as heart, muscle, spleen, and thymus and in all myeloma cell lines examined. The gene was assigned to human chromosome bands 2p21 and 3p22 by in situ hybridization. CIS6 is structurally related to other members of the CIS family and therefore could act as a negative regulator of signal transduction.

Amino Acid Sequence↗

PubMed2000

Subunit structure of the high and low affinity human interleukin-15 receptors.

Radio-iodinated cytokines and monoclonal antibodies directed at the IL-2R beta- and gamma-chains were used to analyze the structure of the cell-surface IL-15 and IL-2 receptors expressed by the human lymphoma cell clone YT-2C2. YT-2C2 cells are IL-2R alpha negative and express IL-2R gamma (15,000 molecules/cell) in excess of IL-2R beta (11,000 molecules/cell). Accordingly, they display a number of beta/gamma complexes of intermediate affinity for IL-2 and IL-15 which is equivalent to the number of beta-chains. Both cytokines compete for binding to this beta/gamma complex. There are about 800 high affinity IL-15 receptors, suggesting the presence of a similar number of IL-15R alpha-chains. Within the common intermediate affinity beta/gamma-complex, the anti-beta-chain A41 mAb defines an epitope which is similarly engaged in IL-2 and IL-15 binding, whereas the anti-beta-chain 284 mAb defines an epitope which does not display similar interaction with either cytokines. Thus, although IL-2 and IL-15 compete for binding to this beta/gamma-complex, they do not use similar binding areas. Cross-linking and immunoprecipitation experiments have shown that the high affinity IL-15 receptors comprises IL-2R beta/gamma, in association with IL-15R alpha and that the three chains can be efficiently cross-linked to IL-15 and co-immunoprecipitated. Contrary to the intermediate affinity situation, high affinity IL-15 binding and subunit cross-linking were not affected by excess amounts of IL-2, A41 or 284 mAb, suggesting that when engaged in the IL-15 high affinity complex, the beta- and gamma-chains adopt different conformations, at least with respect to IL-15 binding. Finally, we provide evidence for the participation of a novel 35 kDa component within the high affinity structure. This component is immunoprecipitated with anti-IL-2R gamma mAb but not with anti-IL-2R beta mAb and might correspond to a truncated form of IL-2R gamma-chain.

Antibodies, Monoclonal↗

PubMed1999

Natural splicing of exon 2 of human interleukin-15 receptor alpha-chain mRNA results in a shortened form with a distinct pattern of expression.

We report the existence of eight different interleukin-15 receptor alpha-chain (IL-15Ralpha) transcripts resulting from exon-splicing mechanisms within the IL-15Ralpha gene. Two main classes of transcripts can be distinguished that do or do not (Delta2 isoforms) contain the exon 2-coding sequence. Both classes were expressed in numerous cell lines and tissues (including peripheral blood lymphocytes) at comparable levels and could be transcribed in COS-7 cells, and the proteins were expressed at the cell surface. Both receptor forms displayed numerous glycosylation states, reflecting differential usage of a single N-glycosylation site as well as extensive O-glycosylations. Whereas IL-15Ralpha bound IL-15 with high affinity, Delta2IL-15Ralpha was unable to bind IL-15, thus revealing the indispensable role of the exon 2-encoded domain in cytokine binding. A large proportion of IL-15Ralpha was expressed at the nuclear membrane with some intranuclear localization, supporting a potential direct action of the IL-15.IL-15Ralpha complex at the nuclear level. In sharp contrast, Delta2IL-15Ralpha was found only in the non-nuclear membrane compartments, indicating that the exon 2-encoded domain (which is shown to contain a potential nuclear localization signal) plays an important role in receptor post-translational routing. Together, our data indicate that exon 2 splicing of human IL-15Ralpha is a natural process that might play regulatory roles at different levels.

Animals↗

PubMed1999

Mannose 6-Phosphate/Insulin-like growth factor II receptor mediates internalization and degradation of leukemia inhibitory factor but not signal transduction.

Leukemia inhibitory factor (LIF) is a multifunctional cytokine belonging to the interleukin-6 subfamily of helical cytokines, all of which use the glycoprotein (gp) 130 subunit for signal transduction. The specific receptor for LIF, gp190, binds this cytokine with low affinity and is also required for signal transduction. We have recently reported that glycosylated LIF produced by transfected Chinese hamster ovary cells also binds to a lectin-like receptor, mannose 6-phosphate/insulin-like growth factor II receptor (Man-6-P/IGFII-R) (Blanchard, F., Raher, S., Duplomb, L., Vusio, P., Pitard, V., Taupin, J. L., Moreau, J. F., Hoflack, B., Minvielle, S., Jacques, Y., and Godard, A. (1998) J. Biol. Chem. 273, 20886-20893). The present study shows that (i) mannose 6-phosphate-containing LIF is naturally produced by a number of normal and tumor cell lines; (ii) other cytokines in the interleukin-6 family do not bind to Man-6-P/IGFII-R; and (iii) another unrelated cytokine, macrophage-colony-stimulating factor, is also able to bind to Man-6-P/IGFII-R in a mannose 6-phosphate-sensitive manner. No functional effects or signal transductions mediated by this lectin-like receptor were observed in various biological assays after LIF binding, and mannose 6-phosphate-containing LIF was as active as non-glycosylated LIF. However, mannose 6-phosphate-sensitive LIF binding resulted in rapid internalization and degradation of the cytokine on numerous cell lines, which suggests that Man-6-P/IGFII-R plays an important role in regulating the amounts of LIF available in vivo.

3T3 Cells↗

PubMed1999

Binding of leukemia inhibitory factor (LIF) to mutants of its low affinity receptor, gp190, reveals a LIF binding site outside and interactions between the two cytokine binding domains.

The gp190 transmembrane protein, the low affinity receptor for the leukemia inhibitory factor (LIF), belongs to the hematopoietin family of receptors characterized by the cytokine binding domain (CBD). gp190 is one of the very few members of this family to contain two such domains. The membrane-proximal CBD (herein called D2) is separated from the membrane-distal one (called D1) by an immunoglobulin-like (Ig) domain and is followed by three fibronectin type III repeats. We used truncated gp190 mutants and a blocking anti-gp190 monoclonal antibody to study the role of these repeats in low affinity receptor function. Our results showed that the D1Ig region was involved in LIF binding, while D2 appeared to be crucial for the proper folding of D1, suggesting functionally important interactions between the two CBDs in the wild-type protein. In addition, a point mutation in the carboxyl terminus of the Ig region strongly impaired ligand binding. These findings suggest that at least two distinct sites, both located within the D1Ig region, are involved in LIF binding to gp190, and more generally, that ligand binding sites on these receptors may well be located outside the canonical CBDs.

Animals↗

PubMed1999

A fusion protein of interleukin-11 and soluble interleukin-11 receptor acts as a superagonist on cells expressing gp130.

Interleukin-11 is a hematopoietic cytokine that signals via the signal transducer gp130. Although gp130 is ubiquitously expressed, interleukine-11 responsiveness is restricted to cells that express the interleukine-11 receptor alpha-subunit. The interleukine-11 receptor alpha-subunit can be functionally replaced by its soluble form indicating that the transmembrane and cytoplasmic parts are not required for signal transduction. Here, we show that a recombinant fusion protein of a fragment of the human interleukine-11 receptor alpha-subunit ectodomain linked to human interleukine-11 acts as a superagonist on cells expressing gp130 but lacking the membrane-bound interleukine-11 receptor alpha-subunit. It induces acute phase protein synthesis in hepatoma cells and efficiently promotes proliferation of Ba/F3 cells stably, transfected with gp130. In these bioassays, the fusion protein of a fragment of the human interleukine-11 receptor alpha-subunit ectodomain linked to human interleukine-11 is 50 times more potent than the combination of interleukine-11 and the soluble interleukine-11 receptor alpha-subunit. Thus, our findings support the concept that covalent fusion of two soluble proteins required for receptor activation dramatically increases their bioactivity.

Acute-Phase Proteins↗

PubMed1999

Definition of receptor binding sites on human interleukin-11 by molecular modeling-guided mutagenesis.

Interleukin-11 (IL-11) belongs to the interleukin-6 (IL-6)-type subfamily of long-chain helical cytokines including IL-6, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), oncostatin M, and cardiotrophin-1, which all share the glycoprotein gp130 as a signal transducing receptor component. IL-11 acts on cells expressing gp130 and the IL-11 receptor (IL-11R) alpha-subunit (IL-11Ralpha). The structural epitopes of IL-11 required for the recruitment of the individual receptor subunits have not yet been defined. Based on the structure of CNTF, a three-dimensional model of human IL-11 was built. Using this model, 10 surface exposed amino acid residues of IL-11 were selected for mutagenesis using analogies to the well-characterized receptor recruitment sites of IL-6, CNTF, and LIF. The respective mutants of human IL-11 were expressed as soluble fusion proteins in bacteria. Their biological activities were determined on HepG2 and Ba/F3-130-11alpha cells. Several mutants with substantially decreased bioactivity and one hyperagonistic mutant were identified and further analyzed with regard to recruitment of IL-11Ralpha and gp130. The low-activity mutant I171D still binds IL-11Ralpha but fails to recruit gp130, whereas the hyperagonistic variant R135E more efficiently engages the IL-11R subunits. The low-activity mutants R190E and L194D failed to bind to IL-11Ralpha. These findings reveal a common mechanism of receptor recruitment in the family of IL-6-type cytokines and offer considerable perspectives for the rational design of IL-11 antagonists and hyperagonists.

Amino Acid Sequence↗