Activation of gp130 signalingin vivo by the IL-6 super-agonist K-7 / D-6 accelerates repopulation of lymphoid organs after irradiation (original) (raw)
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Interleukin-6 triggers the association of its receptor with a possible signal transducer, gp130
Cell, 1989
Interleukin-6 mediates pleiotropic functions in various types of cells through its specific receptor (IL-6-R) the cDNA of which has already been cloned. We report here that an 60 kd single polypeptide chain (IL-6-R) is involved in IL-6 binding and that IL-6 triggers the association of this receptor with a non-ligand-binding membrane glycoprotein, gp130. The association takes place at 37°C within 5 min and is stable for at least 40 min in the presence of IL-6, but does not occur at 0%. Human IL-6-R can associate with a murine gpl30 homolog and is functional in murine cells. Mutant IL-6-R lacking the intracytoplasmic portion is functional, suggesting that the two polypeptide chains interact to involve their extracellular portion. In fact, a soluble IL-6-R lacking the transmembrane and intracytoplasmic domains can associate with gp130 in the presence of IL-6 and mediate its function. These findings indicate that the complex of IL-6 and IL-6-R can interact with a non-ligand-binding membrane glycoprotein, gp130, extracellularly and can provide the IL-6 signal.
Cytokine, 1995
Interleukin 6 (IL-6) is a cytokine with a myriad of biological activities and has been implicated in the pathogenesis of autoimmune, inflammatory and neoplastic diseases (for reviews, see Refs 1-3). The biological activities of IL-6 result from interaction of the cytokine with a complex receptor consisting of two transmembrane glycoproteins. IL-6 first binds with low affinity to an 80 kDa receptor chain (IL-6Rα). The IL-6/IL-6Rα complex then binds with high affinity to the 130 kDa signal transducing chain (gp130 or IL-6R), leading to disulphide linked homodimerization and tyrosine phosphorylation of this molecule and signal transduction. 4 The IL-6 signal transduction pathways are just beginning to be unravelled. Recently it was shown that gp130 can associate with various signal transducing molecules including the transcription factor APRF/STAT3, 5-7 the JAK-Tyk family of protein kinases 4,5,8,9 and the Src-related tyrosine kinase Hck. 10 The IL-6Rα is specific for IL-6, while gp130 is also part of the high affinity receptors for oncostatin M (OM), leukaemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and IL-11, explaining the functional redundancy of this family of cytokines. 11-16 Also at the structural level similarities between these cytokines can be observed: they all belong to the group of long chain cytokines with a similar antiparallel four ␣-helical bundle core structure as growth hormone. 17,18 At the amino acid sequence level these proteins have two regions with notable similarities. 19,20 One of these regions is called the D1-motif and for IL-6 is formed by the amino acids Asn156-Thr164. It is intriguing to speculate that this region is involved in contact formation to the protein gp130 which is common to the receptor complexes of both IL-6, LIF, OM, CNTF and IL-11.
Interleukin 6 and its receptor in the immune response and hematopoiesis
International journal of cell cloning, 1990
Interleukin 6 (IL-6) plays critical roles in the immune response and hematopoiesis. It is a potent B cell differentiation factor inducing antibody-forming plasma cells. It enhances interleukin 3-induced proliferation of hematopoietic stem cells. Furthermore, IL-6 induces maturation of megakaryocytes. In IL-6 transgenic mice, a massive polyclonal plasmacytosis and an increase in the number of mature megakaryocytes in the bone marrow were observed. The data indicated that deregulated expression of the IL-6 gene induced a polyclonal plasmacytosis and could be involved in the oncogenesis of plasma cell neoplasias. IL-6 receptor (IL-6R) was molecularly cloned and found to be an immunoglobulin superfamily having an MW of 80 kDa. Upon the binding of IL-6 to its 80 kDa IL-6R, a second non-binding molecule, gp130 was shown to associate with IL-6R. The complex of IL-6 and soluble IL-6R lacking both transmembrane and cytoplasmic domains could bind gp130 and transduce the signal. The results in...
In Vitro Reconstitution of Recognition and Activation Complexes between Interleukin-6 and gp130
Biochemistry, 2001
Gp130 is a shared signal-transducing receptor for a family of four-helix cytokines, of which interleukin-6 is a prototypic member. IL-6-type cytokines activate gp130 to elicit downstream intracellular JAK/STAT signaling cascades through formation of hetero-oligomeric receptor complexes. Interleukin-6 must first complex with its specific R-receptor (RR) in order to bind and activate gp130. We have dissected the extracellular activation pathway of human gp130 by human IL-6 through reconstitution of soluble complexes representing intermediate and final states in the hierarchical assembly of the IL-6/IL-6RR/ gp130 signaling complex. To isolate these hetero-complexes, we have applied a protein engineering strategy of covalently linking IL-6 to its RR, which results in a "hyperactive" single-chain complex (hyper-IL-6) which we express in both Escherichia coli and insect cells. We have determined that IL-6/IL-RR and the cytokine-binding homology region (CHR) of gp130 (D2D3) form a stable trimolecular "recognition" complex (trimer) consisting of 1IL-6,1 IL-6RR, and 1 gp130-CHR. Addition of the N-terminal (D1) Iglike domain (IGD) of gp130 to the CHR results in a transition to a hexameric "activation" complex containing 2 IL-6, 2IL-6RR, and 2 gp130. These results clearly demonstrate that the recognition and activation complexes are disparate hetero-oligomeric molecular species linked by the recruitment of the gp130 IGD by the unique site III epitope present on all gp130-class cytokines. The results of these studies are relevant to other members of the IL-6 family of gp130-cytokines and address a longstanding question concerning the respective roles of the gp130 CHR and IGD in assembly of the active signaling oligomer.
Regulated expression of gp130 and IL-6 receptor alpha chain in T cell maturation and activation
International Immunology, 1998
The functional receptor for the inflammatory cytokine IL-6 is composed of the ligand binding IL-6 receptor α chain (IL-6Rα) and the signal transducing chain gp130, which is a shared component of multiple cytokine receptors. We analyzed the surface expression of gp130 and IL-6Rα in thymocytes and peripheral T cells. While all thymocytes expressed gp130 throughout thymic maturation, they gained expression of IL-6Rα at the CD4 or CD8 single-positive stage. Approximately 10-30% of the CD4 -CD8 ⍣ and 40-50% of the CD4 ⍣ CD8thymocytes expressed IL-6Rα. Within the CD4 ⍣ CD8population, the IL-6Rαsubpopulation was cortisone sensitive, appeared immature according to the cell surface markers expressed and failed to proliferate after TCR cross-linking. Peripheral T cells were predominantly gp130 ⍣ and IL-6Rα ⍣ , but downregulated gp130 and IL-6Rα expression upon TCR engagement in vitro and in vivo. Peripheral gp130 low/-IL-6Rα low/-T cells expressed surface markers characteristic of memory T cells. We show that gp130 and IL-6Rα are expressed in a regulated manner in T cells, depending on the developmental and functional stage.
Stem Cells, 2006
Interleukin-6 (IL-6) and its soluble receptor (sIL-6R) are major factors for maintenance and expansion of hematopoietic stem cells (HSCs). Sensitivity of HSCs to IL-6 has been previously studied, in part by measuring the expression of IL-6R on the membrane (mIL-6R). Several studies have described the regulation of cell surface expression of IL-6R by several cytokines, but the role of glycoprotein 130 activation has not yet been investigated. In this study, CD133 ؉ cells were purified from adult peripheral blood and were precultured in the absence or presence of 5-fluorouracil (5-FU) for selection of quiescent HSCs. Cells were cultured with continuous or pulsed stimulations of an IL-6 -sIL-6R fusion protein (hyperinterleukin-6 [HIL-6]) to 1) detect mIL-6R by flow cytometry, 2) assess mIL-6R and sIL-6R RNAs by reverse transcription-polymerase chain reaction, 3) measure sIL-6R in supernatants by enzyme-linked immunosorbent assay, 4) analyze cell-cycle status, and 5) perform long-term culture-initiating cell assays. The level of mIL-6R ؊ cells was preserved by 5-FU incubation. HIL-6 increased steady-state mIL-6R RNA and expression rate on HSCs, independently of treatment with 5-FU. Enhanced production of sIL-6R was observed with short pulses of HIL-6 on CD133 ؉ 5-FUpretreated cells. This overproduction of sIL-6R was abrogated by tumor necrosis factor-␣ protease inhibitor-1, an inhibitor of a disintegrin and metalloprotease proteases, suggesting the shedding of mIL-6R. This phenomenon was mediated through the phosphatidylinositol-3kinase pathway and was involved in the maintenance of primitive HSCs. In conclusion, expression and production of IL-6R are tightly regulated and stage specific. We assume that sIL-6R produced by shedding should be involved in autocrine and paracrine loops in the HSC microenvironment.