References of "Haan, Claude 50001912"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailPerspectives for the use of structural information and chemical genetics to develop inhibitors of Janus kinases.
Haan, Claude UL; Behrmann, Iris UL; Haan, Serge UL

in Journal of Cellular & Molecular Medicine (2010), 14(3), 504-27

Gain-of-function mutations in the genes encoding Janus kinases have been discovered in various haematologic diseases. Jaks are composed of a FERM domain, an SH2 domain, a pseudokinase domain and a kinase ... [more ▼]

Gain-of-function mutations in the genes encoding Janus kinases have been discovered in various haematologic diseases. Jaks are composed of a FERM domain, an SH2 domain, a pseudokinase domain and a kinase domain, and a complex interplay of the Jak domains is involved in regulation of catalytic activity and association to cytokine receptors. Most activating mutations are found in the pseudokinase domain. Here we present recently discovered mutations in the context of our structural models of the respective domains. We describe two structural hotspots in the pseudokinase domain of Jak2 that seem to be associated either to myeloproliferation or to lymphoblastic leukaemia, pointing at the involvement of distinct signalling complexes in these disease settings. The different domains of Jaks are discussed as potential drug targets. We present currently available inhibitors targeting Jaks and indicate structural differences in the kinase domains of the different Jaks that may be exploited in the development of specific inhibitors. Moreover, we discuss recent chemical genetic approaches which can be applied to Jaks to better understand the role of these kinases in their biological settings and as drug targets. [less ▲]

Detailed reference viewed: 81 (0 UL)
Full Text
Peer Reviewed
See detailOncostatin M-induced and constitutive activation of the JAK2/STAT5/CIS pathway suppresses CCL1, but not CCL7 and CCL8, chemokine expression
Hintzen, Christoph UL; Haan, Claude UL; Tuckermann, Jan P. et al

in Journal of Immunology (2009), 181(10), 7341-7349

The recruitment of leukocytes to injured tissue is crucial for the initiation of inflammatory responses as well as for immune surveillance to fight tumor progression. In this study, we show that ... [more ▼]

The recruitment of leukocytes to injured tissue is crucial for the initiation of inflammatory responses as well as for immune surveillance to fight tumor progression. In this study, we show that oncostatin M, a member of the IL-6-type cytokine family and potent proinflammatory cytokine stimulates the expression of the chemokines CCL1, CCL7, and CCL8 in primary human dermal fibroblasts at a faster kinetic than IL-1beta or TNF-alpha. The production of CCL1 and CCL8 is important for migration of monocytes, while specific Abs against CCL1 additionally inhibit the migration of T lymphocytes. We identify the mitogen-activated protein kinases ERK1/2 and p38 as crucial factors for the enhanced expression of CCL1 and CCL8. Depletion of the ERK1/2 target genes c-Jun or c-Fos strongly decrease CCL1 and CCL8 expression, while p38 MAPK prolongs the half-life of CCL1, CCL7, and CCL8 mRNA through inhibition of tristetraprolin. None of the STAT transcription factors STAT1, STAT3, or STAT5 stimulate transcription of CCL1 or CCL8. However, we identify a negative regulatory function of activated STAT5 for the gene expression of CCL1. Importantly, not STAT5 itself, but its target gene cytokine inducible SH2-domain containing protein is required for the STAT5 inhibitory effect on CCL1 expression. Finally, we show that constitutive activation of STAT5 through a mutated form of JAK2 (JAK2 V617F) occurring in patients with myeloproliferative disorders similarly suppresses CCL1 expression. Taken together, we identify novel important inflammatory target genes of OSM which are independent of STAT signaling per se, but depend on MAPK activation and are partly repressed through STAT5-dependent expression of cytokine inducible SH2-domain containing protein. [less ▲]

Detailed reference viewed: 65 (1 UL)
Full Text
Peer Reviewed
See detailAn unusual insertion in Jak2 is crucial for kinase activity and differentially affects cytokine responses
Haan, Claude UL; Kroy, Daniela C.; Wüller, Stefan et al

in Journal of Immunology (2009), 182(5), 2969-2977

The Janus kinases, Jaks, constitutively associate with the cytoplasmic region of cytokine receptors and play an important role in a multitude of biological processes. Jak2 dysfunction has been implicated ... [more ▼]

The Janus kinases, Jaks, constitutively associate with the cytoplasmic region of cytokine receptors and play an important role in a multitude of biological processes. Jak2 dysfunction has been implicated in myeloproliferative diseases and leukemia. Although Jaks were studied extensively for many years, the molecular mechanism of Jak activation upon cytokine stimulation of cells is still incompletely understood. In this study, we investigated the importance of an unusual insertion located within the kinase domain in Jak2. We found that the deletion of this insertion, which we named the Jak-specific insertion (JSI), totally abrogates Jak2 autophosphorylation. We further point mutated four residues within the JSI that are conserved in all Jak family members. Three of these mutants showed abrogated or reduced autophosphorylation, whereas the fourth displayed increased autophosphorylation. We found that the phosphorylation state of these mutants is not influenced by other domains of the kinase. Our data further suggest that the JSI is not required for the negative regulation of kinase activity by the suppressor of cytokine signaling proteins, SOCS. Most importantly, we show that mutations in this region differentially affect IFN-gamma and erythropoietin signal transduction. Taken together, the dramatic effects on the phosphorylation status of Jak2 as well as the differential effects on the signaling via different cytokines highlight the importance of this unusual region for the catalytic activity of Jaks. [less ▲]

Detailed reference viewed: 77 (4 UL)
Full Text
Peer Reviewed
See detailInterleukin-27 displays interferon-gamma-like functions in human hepatoma cells and hepatocytes.
Bender, Herdis; Wiesinger, Monique UL; Nordhoff, Carolin et al

in Hepatology (Baltimore, Md.) (2009), 50(2), 585-91

Interleukin-27 (IL-27) is a cytokine belonging to the IL-6/IL-12 cytokine family. It is secreted by antigen-presenting cells, strongly acts on T cells, and also stimulates innate immune cells. In most ... [more ▼]

Interleukin-27 (IL-27) is a cytokine belonging to the IL-6/IL-12 cytokine family. It is secreted by antigen-presenting cells, strongly acts on T cells, and also stimulates innate immune cells. In most studies, the effects of IL-27 on T cells were investigated; however, not much is known about possible effects of IL-27 on other cell types. IL-27 signals via the common IL-6-type cytokine receptor chain gp130 and the IL-27-specific chain WSX-1. Given the importance of gp130 in regulating liver responses such as the acute phase response or liver regeneration, we investigated whether IL-27 could also have a function in liver cells. We find that IL-27 stimulates hepatoma cells and hepatocytes by inducing a sustained signal transducer and activator of transcription (STAT)1 and STAT3 activation. Whereas the STAT3 mediated responses to IL-27 (gamma-fibrinogen and hepcidin induction) are not detectable, we observe an interferon-gamma (IFN-gamma)-like STAT1 response leading to the induction of interferon-regulated proteins such as STAT1, STAT2, interferon response factor (IRF)-1, IRF-9, myxovirus resistance A and guanylate binding protein 2. CONCLUSION: Our study provides evidence for a function of IL-27 in hepatoma cells and hepatocytes and shows that IL-27 responses are not restricted to the classical immune cells. Our results suggest that IL-27 exerts IFN-like functions in liver cells and that it can contribute to the antiviral response in these cells. [less ▲]

Detailed reference viewed: 41 (6 UL)
Full Text
Peer Reviewed
See detailSOCS-mediated downregulation of mutant Jak2 (V617F, T875N and K539L) counteracts cytokine-independent signaling.
Haan, Serge UL; Wuller, S.; Kaczor, Jakub UL et al

in Oncogene (2009), 28(34), 3069-80

Recently, mutations in the gene of Janus kinase 2 (Jak2) were discovered in patients suffering from chronic myeloproliferative disorders (MPD) and leukemia. As suppressors of cytokine signaling (SOCS ... [more ▼]

Recently, mutations in the gene of Janus kinase 2 (Jak2) were discovered in patients suffering from chronic myeloproliferative disorders (MPD) and leukemia. As suppressors of cytokine signaling (SOCS) proteins are potent feedback inhibitors of Jak-mediated signaling, we investigated their role in signal transduction through constitutively active Jak2 mutants. We selected two mutants, Jak2-V617F and Jak2-K539L, found in patients with MPDs and Jak2-T875N identified in acute megakaryoblastic leukemia. We found SOCS family members to be induced through Jak2-V617F in human leukemia cell lines expressing the mutant allele and in stable HEK transfectants inducibly expressing constitutively active Jak2 mutants. SOCS proteins were recruited to the membrane and bound to the constitutively active Jaks. In contrast to wild-type Jak2, the mutant proteins were constitutively ubiquitinated and degraded through the proteasome. Taken together, we show a SOCS-mediated downregulation of the constitutively active, disease-associated mutant Jak2 proteins. Furthermore, a threshold level of mutant Jak expression has to be overcome to allow full cytokine-independent constitutive activation of signaling proteins, which may explain progression to homozygocity in MPDs as well as gene amplification in severe phenotypes and leukemia. [less ▲]

Detailed reference viewed: 98 (1 UL)
Full Text
Peer Reviewed
See detailHypoxia-inducible factor 1alpha is up-regulated by oncostatin M and participates in oncostatin M signaling
Vollmer, Stefan UL; Kappler, Valérie; Kaczor, Jakub UL et al

in Hepatology (Baltimore, Md.) (2009), 2009(3),

The interleukin-6-type cytokine oncostatin M (OSM) acts via the Janus kinase/signal transducer and activator of transcription pathway as well as via activation of mitogen-activated protein kinases and is ... [more ▼]

The interleukin-6-type cytokine oncostatin M (OSM) acts via the Janus kinase/signal transducer and activator of transcription pathway as well as via activation of mitogen-activated protein kinases and is known to critically regulate processes such as liver development and regeneration, hematopoiesis, and angiogenesis, which are also determined by hypoxia with the hypoxia-inducible factor 1alpha (HIF1alpha) as a key component. Here we show that treatment of hepatocytes and hepatoma cells with OSM leads to an increased protein level of HIF1alpha under normoxic and hypoxic conditions. Furthermore, the OSM-dependent HIF1alpha increase is mediated via Janus kinase/signal transducer and activator of transcription 3 and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 pathways. OSM-mediated HIF1alpha up-regulation did not result from an increase in HIF1alpha protein stability but from increased transcription from the HIF1alpha gene. In addition, we show that the OSM-induced HIF1alpha gene transcription and the resulting enhanced HIF1alpha protein levels are important for the OSM-dependent vascular endothelial growth factor and plasminogen activator inhibitor 1 gene induction associated with several diseases. Conclusion: HIF1alpha levels increase significantly after treatment of hepatocytes and hepatoma cells with OSM, and HIF1alpha contributes to OSM downstream signaling events, pointing to a cross-talk between cytokine and hypoxia signaling in processes such as liver development and regeneration. (HEPATOLOGY 2009.). [less ▲]

Detailed reference viewed: 45 (1 UL)
Peer Reviewed
See detailDual role of the Jak1 FERM and kinase domains in cytokine receptor binding and in stimulation-dependent Jak activation
Haan, Serge UL; Margue, Christiane UL; Engrand, A. et al

in Journal of Immunology (2008), 180(2), 998-1007

Jak1 is a tyrosine kinase that noncovalently forms tight complexes with a variety of cytokine receptors and is critically involved in signal transduction via cytokines. Jaks are predicted to have a 4.1 ... [more ▼]

Jak1 is a tyrosine kinase that noncovalently forms tight complexes with a variety of cytokine receptors and is critically involved in signal transduction via cytokines. Jaks are predicted to have a 4.1, ezrin, radixin, moesin (FERM) domain at their N terminus. FERM domains are composed of three structurally unrelated subdomains (F1, F2, and F3) which are in close contact to one another and form the clover-shaped FERM domain. We generated a model structure of the Jak1 FERM domain, based on solved FERM structures and the alignments with other FERM domains. To destabilize different subdomains and to uncover their exact function, we mutated specific hydrophobic residues conserved in FERM domains and involved in hydrophobic core interactions. In this study, we show that the structural integrity of the F2 subdomain of the FERM domain of Jak1 is necessary to bind the IFN-gammaRalpha. By mutagenesis of hydrophobic residues in the hydrophobic core between the three FERM subdomains, we find that the structural context of the FERM domain is necessary for the inhibition of Jak1 phosphorylation. Thus, FERM domain mutations can have repercussions on Jak1 function. Interestingly, a mutation in the kinase domain (Jak1-K907E), known to abolish the catalytic activity, also leads to an impaired binding to the IFN-gammaRalpha when this mutant is expressed at endogenous levels in U4C cells. Our data show that the structural integrity of both the FERM domain and of the kinase domain is essential for both receptor binding and catalytic function/autoinhibition. [less ▲]

Detailed reference viewed: 106 (9 UL)
Full Text
Peer Reviewed
See detailRecombinant interleukin-24 lacks apoptosis-inducing properties in melanoma cells
Kreis, Stephanie UL; Philippidou, Demetra UL; Margue, Christiane UL et al

in PLoS ONE (2007), 2(12), 1300

IL-24, also known as melanoma differentiation antigen 7 (mda-7), is a member of the IL-10 family of cytokines and is mainly produced by Th(2) cells as well as by activated monocytes. Binding of IL-24 to ... [more ▼]

IL-24, also known as melanoma differentiation antigen 7 (mda-7), is a member of the IL-10 family of cytokines and is mainly produced by Th(2) cells as well as by activated monocytes. Binding of IL-24 to either of its two possible heterodimeric receptors IL-20R1/IL-20R2 and IL-22R/IL-20R2 activates STAT3 and/or STAT1 in target tissues such as lung, testis, ovary, keratinocytes and skin. To date, the physiological properties of IL-24 are still not well understood but available data suggest that IL-24 affects epidermal functions by increasing proliferation of dermal cells. In stark contrast to its "normal" and physiological behaviour, IL-24 has been reported to selectively and efficiently kill a vast variety of cancer cells, especially melanoma cells, independent of receptor expression and Jak-STAT signalling. These intriguing properties have led to the development of adenovirally-expressed IL-24, which is currently being evaluated in clinical trials. Using three different methods, we have analysed a large panel of melanoma cell lines with respect to IL-24 and IL-24 receptor expression and found that none of the investigated cell lines expressed sufficient amounts of functional receptor pairs and therefore did not react to IL-24 stimulation with Jak/STAT activation. Results for three cell lines contrasted with previous studies, which reported presence of IL-24 receptors and activation of STAT3 following IL-24 stimulation. Furthermore, evaluating four different sources and modes of IL-24 administration (commercial recombinant IL-24, bacterially expressed GST-IL-24 fusion protein, IL-24 produced from transfected Hek cells, transiently over-expressed IL-24) no induction or increase in cell death was detected when compared to appropriate control treatments. Thus, we conclude that the cytokine IL-24 itself has no cancer-specific apoptosis-inducing properties in melanoma cells. [less ▲]

Detailed reference viewed: 66 (5 UL)
Full Text
Peer Reviewed
See detailA cost effective non-commercial ECL-solution for Western blot detections yielding strong signals and low background
Haan, Claude UL; Behrmann, Iris UL

in Journal of Immunological Methods (2007), 318(1-2), 11-9

We compared several alternative ECL solutions for Western blot detection of endogenous proteins in whole cell lysates using inexpensive, commercially available reagents. Starting from an existing protocol ... [more ▼]

We compared several alternative ECL solutions for Western blot detection of endogenous proteins in whole cell lysates using inexpensive, commercially available reagents. Starting from an existing protocol based on p-coumaric acid (pCA) as enhancer, we found that the ECL solution containing 4-iodophenylboronic acid (4IPBA) generated strong specific signals and low background chemiluminescence. We optimised the luminol, 4IPBA and hydrogenperoxide concentrations of this 4IPBA-ECL solution. The optimised 4IPBA-ECL solution (100 mM Tris/HCl pH 8.8, 1.25 mM luminol, 2 mM 4IPBA, 5.3 mM hydrogenperoxide) shows a greatly increased signal intensity compared to the initial pCA-ECL protocol and to some commercially available ECL solutions. In addition, the optimised 4IPBA-ECL solution also generates much lower background chemiluminescence than other non-commercial ECL solutions using p-coumaric acid or 4-iodophenol as enhancers. The 4IPBA-ECL solution was stable when stored but had the lowest background when prepared freshly from stock solutions. Thus, we present an optimised protocol for a well-performing inexpensive ECL solution which is an alternative to expensive commercial ECL solutions and which achieves a better signal and lower background than the commercial solutions tested. [less ▲]

Detailed reference viewed: 66 (2 UL)
Full Text
Peer Reviewed
See detailJaks and cytokine receptors - an intimate relationship
Haan, Claude UL; Kreis, Stephanie UL; Margue, Christiane UL et al

in Biochemical Pharmacology (2006), 72(11), 1538-46

Most cytokine receptors lack intrinsic kinase activity and many of them signal via Janus kinases (Jaks). These tyrosine kinases are associated with cytokine receptor subunits, they become activated upon ... [more ▼]

Most cytokine receptors lack intrinsic kinase activity and many of them signal via Janus kinases (Jaks). These tyrosine kinases are associated with cytokine receptor subunits, they become activated upon receptor triggering and subsequently activate downstream signalling events, e.g. the phosphorylation of STAT transcription factors. The successful interplay between cytokines, their receptors and the connected Jaks not only determines signalling competence but is also vital for intracellular traffic, stability, and fate of the cognate receptors. Here, we will discuss underlying mechanisms as well as some structural features with a focus on Jak1 and two of the signal transducing receptor subunits of interleukin (IL)-6 type cytokines, gp130 and OSMR. Regions that are critically involved in Jak-binding have been identified for many cytokine receptor subunits. In most cases the membrane-proximal parts comprising the box1 and box2 regions within the receptor are involved in this association while, within Jaks, the N-terminal FERM domain, possibly together with the SH2-like domain, are pivotal for binding to the relevant receptors. The exclusive membrane localisation of Jaks depends on their ability to associate with cytokine receptors. For gp130 and Jak1, it was shown that the cytokine receptor/Jak complex can be regarded as a receptor tyrosine kinase since both molecules have the same diffusion dynamics and are virtually undissociable. Furthermore, Jaks take an active role in the regulation of the surface expression of at least some cytokine receptors, including the OSMR and this may provide a quality control mechanism ensuring that only signalling-competent receptors (i.e. those with an associated Jak) would be enriched at the cell surface. [less ▲]

Detailed reference viewed: 69 (5 UL)
Peer Reviewed
See detailThe Jak1 SH2 domain does not fulfill a classical SH2 function in Jak/STAT signaling but plays a structural role for receptor interaction and up-regulation of receptor surface expression
Radtke, S.; Haan, Serge UL; Jörissen, A. et al

in Journal of Biological Chemistry (2005), 280(27), 25760-8

The presence of a Src homology 2 (SH2) domain sequence similarity in the sequence of Janus kinases (Jaks) has been discussed since the first descriptions of these enzymes. We performed an in depth study ... [more ▼]

The presence of a Src homology 2 (SH2) domain sequence similarity in the sequence of Janus kinases (Jaks) has been discussed since the first descriptions of these enzymes. We performed an in depth study to determine the function of the Jak1 SH2 domain. We investigated the functionality of the Jak1 SH2 domain by stably reconstituting Jak1-defective human fibrosarcoma cells U4C with endogenous amounts of Jak1 in which the crucial arginine residue Arg466 within the SH2 domain has been replaced by lysine. This mutant still binds to the receptor subunits gp130 and OSMR. Moreover, the SH2 R466K mutation does not affect the subcellular distribution of Jak1 as assessed by cell fractionation and confocal microscopy of cells expressing endogenous levels of non-tagged or a yellow fluorescent protein (YFP)-tagged Jak1-R466K, respectively. Likewise, the signaling capacity of Jak1 was not affected by this point mutation. However, we found that the SH2 domain is structurally important for cytokine receptor binding and surface expression of the OSMR. [less ▲]

Detailed reference viewed: 73 (2 UL)
Peer Reviewed
See detailMultiple reasons for an inefficient STAT1 response upon IL-6-type cytokine stimulation
Haan, Serge UL; Keller, J. F.; Behrmann, Iris UL et al

in Cellular Signalling (2005), 17(12), 1542-50

IL-6-type cytokines play an important role during inflammation and the immune response. In addition, they are involved in haematopoiesis, liver and neuronal regeneration, embryonic development and ... [more ▼]

IL-6-type cytokines play an important role during inflammation and the immune response. In addition, they are involved in haematopoiesis, liver and neuronal regeneration, embryonic development and fertility. We found that IL-6-type cytokine stimulation of cell lines and primary human macrophages results in a different distribution of the DNA-binding competent STAT dimer species in the cytosol and nucleus as demonstrated by electrophoretic mobility shift assays. In the absence of detergent, STAT3/STAT3, STAT1/STAT3 were the predominant species in the cytoplasm while STAT3/STAT3 was predominant in the nucleus. However, in detergent containing total cellular lysates and nuclear fractions prepared with detergent containing buffers, the STAT1/STAT1 homodimer was as prominent or even more prominent than STAT3/STAT3 and STAT1/STAT3. We were interested in the cause of this discrepancy since STAT1-regulated genes have not been described to be expressed upon IL-6-type cytokine stimulation. In addition to the more transient STAT1 activation, IL-6-type cytokines such as IL-6 and OSM lead to a much less efficient STAT1 activation compared to the potent STAT1 activators IFNgamma and IFNalpha. Studies with STAT1-deficient cells revealed that STAT1 activation does not seem to be an important competitive process to STAT3 activation arguing again for a very inefficient STAT1 activation upon IL-6-type cytokine stimulation. We also describe that pY-STAT3 is much more efficiently shuttled into the nucleus than pY-STAT1. [less ▲]

Detailed reference viewed: 75 (2 UL)
Peer Reviewed
See detailJanus kinase (Jak) subcellular localization revisited: the exclusive membrane localization of endogenous Janus kinase 1 by cytokine receptor interaction uncovers the Jak.receptor complex to be equivalent to a receptor tyrosine kinase
Behrmann, Iris UL; Smyczek, Tanja; Heinrich, Peter C. et al

in Journal of Biological Chemistry (2004), 279(34), 35486-93

The Janus kinases are considered to be cytoplasmic kinases that constitutively associate with the cytoplasmic region of cytokine receptors, and the Janus kinases (Jaks) are crucial for cytokine signal ... [more ▼]

The Janus kinases are considered to be cytoplasmic kinases that constitutively associate with the cytoplasmic region of cytokine receptors, and the Janus kinases (Jaks) are crucial for cytokine signal transduction. We investigated Jak1 localization using subcellular fractionation techniques and fluorescence microscopy (immunofluorescence and yellow fluorescent protein-tagged Jaks). In the different experimental approaches we found Jak1 (as well as Jak2 and Tyk2) predominantly located at membranes. In contrast to previous reports we did not observe Jak proteins in significant amounts within the nucleus or in the cytoplasm. The cytoplasmic localization observed for the Jak1 mutant L80A/Y81A, which is unable to associate with cytokine receptors, indicates that Jak1 does not have a strong intrinsic membrane binding potential and that only receptor binding is crucial for the membrane recruitment. Finally we show that Jak1 remains a membrane-localized protein after cytokine stimulation. These data strongly support the hypothesis that cytokine receptor.Janus kinase complexes can be regarded as receptor tyrosine kinases. [less ▲]

Detailed reference viewed: 63 (2 UL)
Peer Reviewed
See detailLong term association of the cytokine receptor gp130 and the Janus kinase Jak1 revealed by FRAP analysis
Giese, B.; Au-Yeung, C. K.; Herrmann, A. et al

in Journal of Biological Chemistry (2003), 278(40), 39205-13

Signal transduction through cytokine receptors is mediated mainly by non-covalently associated Jak tyrosine kinases. By confocal microscopy, the cytokine receptor gp130 and Jak1, fused with either yellow ... [more ▼]

Signal transduction through cytokine receptors is mediated mainly by non-covalently associated Jak tyrosine kinases. By confocal microscopy, the cytokine receptor gp130 and Jak1, fused with either yellow (YFP) or cyan (CFP) fluorescent protein, were found to be colocalized predominantly at intracellular vesicular structures and at the plasma membrane. Quantitative fluorescence recovery after photobleaching (FRAP) analysis at the plasma membrane revealed equal mobilities for gp130-YFP and Jak1-YFP. Thus, Jak1-YFP diffuses like a transmembrane protein indicating that membrane-bound Jak1 does not exchange rapidly with cytosolic Jaks. Applying a novel dual-color FRAP approach we found that immobilization of gp130-CFP by a pair of monoclonal antibodies led to a corresponding immobilization of co-transfected Jak1-YFP. We conclude from these findings that Jak1, once bound to a gp130 molecule, does not exchange between different receptors at the plasma membrane neither via the cytoplasmic compartment nor via a membrane-associated state. [less ▲]

Detailed reference viewed: 65 (1 UL)
Peer Reviewed
See detailNovel role of Janus kinase 1 in the regulation of oncostatin M receptor surface expression
Radtke, S.; Hermanns, H. M.; Haan, Claude UL et al

in Journal of Biological Chemistry (2002), 277(13), 11297-305

The oncostatin M receptor (OSMR) is part of a heterodimeric receptor complex that mediates signal transduction of the pleiotropic cytokine OSM via a signaling pathway involving Janus kinases (Jaks) and ... [more ▼]

The oncostatin M receptor (OSMR) is part of a heterodimeric receptor complex that mediates signal transduction of the pleiotropic cytokine OSM via a signaling pathway involving Janus kinases (Jaks) and transcription factors of the signal transducers and activators of transcription (STAT) family. Upon heterologous expression of the OSMR in several cell lines, we observed that its surface expression was significantly enhanced by coexpression of the Janus kinases Jak1, Jak2, and Tyk2 but not Jak3. Chimeric receptors consisting of the extracellular region of the interleukin-5 receptor beta chain and the transmembrane and intracellular part of the OSMR were similarly up-regulated on the plasma membrane when Jak1 was coexpressed. The overall expression level of these constructs did not change significantly, but Jak1 coexpression increased the amount of endoglycosidase H-resistant, fully processed OSMR chimeras. Using mutated receptor and Jak1 constructs, we were able to demonstrate that association of Jak1 with the membrane proximal region of the receptor, but not its kinase activity, is necessary for this effect. Moreover, deletion of the OSMR box1/2 region also resulted in an improved surface expression indicating that this region may contain a signal preventing efficient receptor surface expression in the absence of associated Jaks. Finally we demonstrate that in Jak1-deficient cells, the endogenous OSMR is significantly down-regulated, an effect that can be reversed by transient expression of Jak1 in these cells. [less ▲]

Detailed reference viewed: 58 (1 UL)
Peer Reviewed
See detailA single amino acid substitution (Trp(666)-->Ala) in the interbox1/2 region of the interleukin-6 signal transducer gp130 abrogates binding of JAK1, and dominantly impairs signal transduction
Haan, Claude UL; Hermanns, H. M.; Heinrich, P. C. et al

in Biochemical Journal (2001), 349(Pt 1), 261-6

gp130 is the common signal-transducing receptor chain of interleukin (IL)-6-type cytokines. Here we describe, for the first time, a single amino acid substitution (Trp(666)-->Ala) in the membrane-proximal ... [more ▼]

gp130 is the common signal-transducing receptor chain of interleukin (IL)-6-type cytokines. Here we describe, for the first time, a single amino acid substitution (Trp(666)-->Ala) in the membrane-proximal interbox1/2 region that abrogates activation of STAT (signal transducer and activator of transcription) transcription factors and the proliferative response of pro-B-cell transfectants. Moreover, association of the Janus kinase JAK1 is prevented. No signalling of heterodimeric IL-5 receptor (IL-5R)/gp130 chimaeras occurs in COS-7 cells, even when only a single cytoplasmic chain of a gp130 dimer contains the Trp(666)Ala mutation, indicating that it acts dominantly. [less ▲]

Detailed reference viewed: 79 (3 UL)
Peer Reviewed
See detailStructural requirements of the interleukin-6 signal transducer gp130 for its interaction with Janus kinase 1: the receptor is crucial for kinase activation
Haan, Claude UL; Heinrich, P. C.; Behrmann, Iris UL

in Biochemical Journal (2001), 361(Pt 1), 105-11

We analysed the interaction of gp130, the common signal-transducing receptor chain of interleukin (IL)-6 type cytokines, with Jak1, the Janus family kinase which is crucial for signal transduction of this ... [more ▼]

We analysed the interaction of gp130, the common signal-transducing receptor chain of interleukin (IL)-6 type cytokines, with Jak1, the Janus family kinase which is crucial for signal transduction of this group of cytokines. With a truncated chimaeric IL-5Rbeta-gp130 receptor expressed in COS-7 cells, we show that the membrane-proximal 69 amino acids are sufficient to mediate Jak1 binding and activation. Deletion of box2 drastically reduced binding of endogenous, but not of overexpressed, Jak1. Several point mutations in the membrane-proximal region of gp130 (W652A, P671/P672A, F676A, Y683F, where W, A, P, F and Y are tryptophan, alanine, proline, phenylalanine and tyrosine) did not affect Jak1 association. However, stimulation of chimaeric receptors with the mutations P671/P672A and F676A in the interbox1/box2 region resulted in a reduced activation of STAT (signal transducer and activator of transcription) transcription factors. Most importantly, signalling by the receptor with the box1 mutation W652A was totally abrogated. Although this mutation did not affect Jak1 association, stimulation-dependent phosphorylation of Jak1 was prevented. The W652 mutation acts dominantly, since no signalling occured even when only a single cytoplasmic chain of a gp130 dimer contained the mutation. Our data demonstrate that the mere proximity of Jaks in an activated receptor complex is not sufficient to mediate their activation. Rather, it seems that parts of the receptor, including the box1 region, are involved in positioning Jaks correctly so that ligand-induced receptor dimerization and reorientation can lead to their mutual activation and subsequently to downstream signalling events. [less ▲]

Detailed reference viewed: 54 (1 UL)
Peer Reviewed
See detailMapping of a region within the N terminus of Jak1 involved in cytokine receptor interaction
Haan, Claude UL; Isharc, H.; Hermanns, H. M. et al

in Journal of Biological Chemistry (2001), 276(40), 37451-8

Janus kinase 1 (Jak1) is a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors. Here we show that the in vitro translated N-terminal domains of Jak1 are ... [more ▼]

Janus kinase 1 (Jak1) is a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors. Here we show that the in vitro translated N-terminal domains of Jak1 are sufficient for binding to a biotinylated peptide comprising the membrane-proximal 73 amino acids of gp130, the signal-transducing receptor chain of interleukin-6-type cytokines. By the fold recognition approach amino acid residues 36-112 of Jak1 were predicted to adopt a beta-grasp fold, and a structural model was built using ubiquitin as a template. Substitution of Tyr(107) to alanine, a residue conserved among Jaks and involved in hydrophobic core interactions of the proposed beta-grasp domain, abrogated binding of full-length Jak1 to gp130 in COS-7 transfectants. By further mutagenesis we identified the loop 4 region of the Jak1 beta-grasp domain as essential for gp130 association and gp130-mediated signal transduction. In Jak1-deficient U4C cells reconstituted with the loop 4 Jak1 mutants L80A/Y81A and Delta(Tyr(81)-Ser(84)), the interferon-gamma, interferon-alpha, and interleukin-6 responses were similarly impaired. Thus, loop 4 of the beta-grasp domain plays a role in the association of Jak1 with both class I and II cytokine receptors. Taken together the structural model and the mutagenesis data provide further insight into the interaction of Janus kinases with cytokine receptors. [less ▲]

Detailed reference viewed: 56 (1 UL)
Peer Reviewed
See detailTermination of IL-6-induced STAT activation is independent of receptor internalization but requires de novo protein synthesis
Thiel, S.; Sommer, U.; Kortylewski, M. et al

in FEBS Letters (2000), 470(1), 15-9

The interleukin-6 (IL-6) receptor complex comprises the IL-6 receptor (IL-6R, gp80) and the signal transducer gp130. Binding of IL-6 to its receptor results in dimerization of gp130, activation of the Jak ... [more ▼]

The interleukin-6 (IL-6) receptor complex comprises the IL-6 receptor (IL-6R, gp80) and the signal transducer gp130. Binding of IL-6 to its receptor results in dimerization of gp130, activation of the Jak/STAT pathway, and in a down-regulation of IL-6 binding sites by endocytosis. The STAT activation after stimulation is transient, being maximal after 15-30 min and disappearing after 60-90 min. The mechanism which leads to the termination of the signal is still unknown.In this paper we have studied whether the down-modulation of the STAT signal requires the endocytosis of the receptor complex. Our results suggest that the desensitization of the IL-6 signal is not due to internalization of the receptor complex but requires de novo protein synthesis. [less ▲]

Detailed reference viewed: 59 (1 UL)
Peer Reviewed
See detailSignalling of interleukin-6 type cytokines via gp130, leukemia inhibitory factor (LIF) receptor and oncostatin M receptor
Behrmann, Iris UL; Hermanns, H. M.; Haan, Claude UL et al

in European Cytokine Network (2000), 11(3), 491-2

Detailed reference viewed: 29 (1 UL)