Interleukin-6 receptor and signals.
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Amino Acid Sequence↗
Biomedical subjects
T Taga
Publications and source records attributed to T Taga.
Role of a two-chain IL-6 receptor system in immune and hematopoietic cell regulation.
Three factors with distinct function are involved in the regulation of the B-cell response into antibody-producing cells: (1) a factor for the activation of resting B cells (BSF1/IL-4), (2) a factor for the growth of activated B cells (BCGFII/IL-5), and (3) a factor for the final maturation of B cells into antibody-producing cells (BSF2/IL-6). The cDNAs for these three molecules have been cloned, and studies with recombinant molecules demonstrated that their individual functions were not confined to the B-lineage cells; they were found to have a wide variety of biological functions. A typical example of a pleiotropic function of such interleukins is BSF2/IL-6. BSF2/IL-6 is not only a B-cell-differentiation factor, but also is a potent growth factor for myeloma cells. Moreover, BSF2/IL-6 acts as hepatocyte-stimulating factor to induce acute-phase proteins and multicolony-stimulating factor to activate hematopoietic stem cells. It appears that BSF2/IL-6 plays an essential role in the host defense mechanisms against infections, inflammation, and injury. Receptors for BSFs have not yet been molecularly cloned because of the low density of receptor molecules. Recently, the cloning of the cDNA for BSF2/IL-6 receptor has been achieved and its molecular structure and the signals transduced through it are described herein.
Amino Acid Sequence↗
Critical cytoplasmic region of the interleukin 6 signal transducer gp130 is conserved in the cytokine receptor family.
Interleukin 6 (IL-6) signal is transduced through gp130 that associates with a complex of IL-6 and IL-6 receptor. Truncations or amino acid substitutions offe introduced in the cytoplasmic region of human gp130, and the mutant cDNAs were transfected into murine interleukin 3-dependent cells to determine amino acid residues critical for generating the IL-6-mediated growth signal. In the 277-amino acid cytoplasmic region of gp130, a 61-amino acid region proximal to the transmembrane domain was sufficient for generating the growth signal. In this region, two short segments were significantly homologous with other cytokine-receptor family members. One segment is conserved in almost all members of the family, and the other is found especially in granulocyte colony-stimulating factor receptor, interleukin 2 receptor beta chain, erythropoietin receptor, KH97 (a granulocyte/macrophage colony-stimulating factor receptor-associated molecule), and interleukin 3 receptor. gp130 molecules with mutations in either of these two segments could not transduce growth signal. Loss of signal-transducing ability of gp130 with such a mutation coincided with disappearance of IL-6-induced tyrosine phosphorylation of gp130.
Amino Acid Sequence↗
Structure of benzyloxycarbonyl-L-isoleucyl-L-alanyl-alpha- aminoisobutyryl-alpha-aminoisobutyrate methyl ester, Z-L-Ile-L-Ala-Aib-Aib-OMe.
C26H40N4O7, Mr = 520.6, tetragonal, P4(3)2(1)2, a = 10.433 (1), c = 54.476 (7) A, V = 5930 (1) A3, Z = 8, Dm = 1.155 (3), Dx = 1.166 Mg m-3, lambda (Cu K alpha) = 1.54178 A, mu = 0.665 mm-1, F(000) = 2240, T = 295 K, R = 0.057 for 2037 observed reflections. The tetrapeptide adopts a type II beta-turn conformation with an extremely weak 4----1 intramolecular hydrogen bond [3.479 (7) A]. The molecules are held together in the crystal by three kinds of N-H---O intermolecular hydrogen bonds.
Amino Acid Sequence↗
Retinoic acid-induced growth inhibition of a human myeloma cell line via down-regulation of IL-6 receptors.
In this report we demonstrate that retinoic acid (RA) down-regulated the number of IL-6R on human leukocyte cell lines, including the myeloma cell line AF10, and two B cell hybridomas that correspond to cells at earlier stages of B cell development. Using AF10 cells, whose growth was determined to be mediated by the autocrine action of IL-6, we found that RA reduction of IL-6R was concentration-dependent over a range of 10(-11) to 10(-5) M and corresponded to the ability of the retinoid to inhibit cell proliferation. The down-regulation of IL-6R number by RA was accompanied by reduced IL-6R mRNA expression. RA did not affect endogeneous IL-6 synthesis or secretion from AF10 cells. However, addition of exogenous rIL-6 could overcome RA-induced growth inhibition. Menthol, a structurally unrelated compound to RA, also suppressed IL-6R expression and, correspondingly, inhibited cell growth. Taken together, our results suggest that the antiproliferative action of RA on AF10 cells is caused by reduction of IL-6R expression and subsequent inhibition of IL-6-mediated autocrine growth. These findings suggest the possibility that down-regulation of IL-6R is a means by which RA can modulate immune function.
Cell Division↗
Cytokine regulation of localized inflammation. Induction of activated B cells and IL-6-mediated polyclonal IgG and IgA synthesis in inflamed human gingiva.
It is well established that increased numbers of plasma cells occur in the localized tissues of chronic inflammatory diseases such as adult periodontitis, and enzymatic isolation has shown that most B lineage cells produce IgG-subclass with some IgA-subclass responses. It would be of importance to determine if excess production of cytokines in the localized lesion account for these responses and in the present study we have assessed gingival mononuclear cell (GMC) supernatants for cytokines that activate B cells including IL-6R expression and for levels of IL-6 present. Inasmuch as limited numbers (approximately 1 to 3 x 10(6) cells) of GMC were obtained from surgically removed tissues (approximately 400 mg), we have focused on the analysis of IL-6 production by GMC in this study. Further, initial evidence of additional cytokines that are produced by GMC and induce expression of IL-6R on resting B cells has been obtained. The GMC and PBMC from individual patients were cultured in the presence (or absence) of Con A. Higher levels of IL-6 were produced spontaneously by GMC when compared with Con A-stimulated PBMC. When PBMC cultures were supplemented with GMC supernatants obtained from the same patient, high numbers of spot-forming cells (SFC), mainly of IgG followed by IgA isotype, were seen. The induction of SFC by GMC supernatants was inhibited by incubation with a goat anti-human IL-6 antibody. When the effect of GMC supernatants on subclasses of PBMC SFC was determined, the response was IgG1 greater than IgG2 greater than IgG3 = IgG4 and IgA1 greater than IgA2, a pattern remarkably similar to the distribution of plasma cells in the GMC itself. To assess for cytokines in GMC supernatants that mediated B cell activation, supernatants containing anti-IL-6 were cultured with PBMC or purified B cells for 72 h. This treatment induced small proliferative B cell responses and elevated expression of IL-6R on B cells, but did not induce SFC responses. Further, incubation of B cells with GMC supernatants induced resting B cells (G0/G1) to enter the cell cycle (S and G2/M). Addition of human rIL-6 to these cultures on day 3 restored IgG- and IgA-subclass SFC responses by day 7. Cytokine-induced IL-6R expression also occurred in vivo because freshly isolated GMC expressed high levels of this receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
B-Lymphocytes↗
Histamine influences the expression of the interleukin-6 receptor on human lymphoid, monocytoid and hepatoma cell lines.
Based on our earlier data on the enhancing effect of histamine on the action of interleukin-6 (IL-6), we have studied the molecular mechanisms of these interactions. The effect of histamine was investigated on the binding of 125I-IL-6 by B lymphoma cell line CESS, monocytoid cell line U937 and hepatoma cell line HepG2. Histamine increases the IL-6 binding by CESS cells and inhibits that by U937 and HepG2 cells. Using H1 receptor (cetirizin and loderix) and H2 receptor (cimetidine and ranitidine) specific antagonists, an H1-dependent stimulation of IL-6 binding by CESS cells was found. In contrast, down-regulation of IL-6 binding by histamine was clearly mediated through H2 receptors. On U937 cells, using a monoclonal antibody reacting with the 80 kd chain of the human IL-6 receptor, and H2-receptor mediated inhibition of IL-6 receptor expression was found by FACS analysis.
Carcinoma, Hepatocellular↗
Anti-murine IL-6 receptor antibody inhibits IL-6 effects in vivo.
Thrombopoiesis, as well as antibody production, is one of the major events in which interleukin-6 (IL-6) has been reported to be involved. Polyclonal anti-murine IL-6 receptor antibody was prepared to examine the effect of the antibody on these events in IL-6-treated mice. Administration of the anti-mIL-6R antibody inhibited the IL-6-induced increase in the number of platelets. Enhancement of the serum level of DNP-specific antibody by intraperitoneal injection of IL-6 was inhibited completely with simultaneous administration of the anti-mIL-6R antibody. The level of DNP-specific antibody was decreased, even below the basal value, by the higher dose of anti-mIL-6R antibody, indicating its effect also on endogenous IL-6. This work provides evidence that anti-IL-6R antibody inhibits IL-6 function in vivo, and provides an animal model of the therapeutic use of anti-IL-6R antibody for IL-6-related disease.
Animals↗
Neuronal differentiation of Ewing's sarcoma induced by cholera toxin B and bromodeoxyuridine--establishment of Ewing's sarcoma cell line and histochemical study.
An Ewing's sarcoma (ES) cell line was established from a metastatic bone marrow specimen in a patient with advanced disease, and some histochemical characteristics were investigated by neuronal differentiation induced with cholera toxin B (CTB) and bromodeoxyuridine (BrdU). Neuronal differentiation was investigated by the expression of neurofilament and Leu-7, and glial differentiation was observed by expression of S-100 protein. Neurofilament (NF) and Leu-7 were positive in ES cells and these were expressed more intensively by induction with CTB than with BrdU. There was no expression of S-100 protein in untreated or differentiated ES cells. ES cells became differentiated to neuronal cells with CTB and BrdU, but it was not observed, that ES cells had the potential to differentiate to glial cells. It appears that ES is of more primitive neural origin than neuroblastoma, primitive neuroectodermal tumors and other related neural tumors.
Antigens, Differentiation↗
Human appendix B cells naturally express receptors for and respond to interleukin 6 with selective IgA1 and IgA2 synthesis.
Past studies have shown that freshly isolated human B cells from peripheral blood and tonsils do not express IL-6 receptors (IL-6R); however, mitogen or antigen activation of these B cells induces IL-6R and responsiveness to IL-6. In this study, we have shown that a high proportion of B cells enzymatically dissociated from human appendix, a gut-associated lymphoreticular tissue (GALT), expresses the IL-6R, and that recombinant human IL-6 induces significant increases in the number of Ig-producing cells. The recombinant human IL-6-induced increase in Ig-producing cells is restricted to the IgA isotype. Further, IgA2 is the major subclass; however, significant numbers of IgA1 producing cells are also seen. In contrast, human tonsillar and peripheral blood B cells express low levels of IL-6R, and exogenous IL-6 does not increase numbers of Ig-producing cells. When PBMC or tonsillar cells are stimulated with PWM, the former display an equal distribution of IgA1 and IgA2 secreting cells, while tonsillar B cells are mainly of the IgA1 subclass. The distribution of surface Ig-positive (sIg+) B cells in the appendix B cell population is sIgA+ greater than sIgG+ greater than sIgM+, and the sIgA+ B cells express higher levels of IL-6R when compared with sIgG+ or sIgM+ B cells. These studies show that human appendix contains B cell subsets that constitutively express IL-6R, and that a high proportion of these cells are committed to the IgA isotype. Furthermore, higher numbers of IL-6 responsive IgA2 B cells are present in the human appendix as compared to tonsils or PBMC.
Appendix↗
Molecular cloning and expression of an IL-6 signal transducer, gp130.
Interleukin-6 (IL-6) signal is transduced through a membrane glycoprotein, gp130, which associates with IL-6 receptor (IL-6-R). A cDNA encoding human gp130 has been cloned, revealing that it consists of 918 amino acids with a single transmembrane domain. The extracellular region comprises six units of a fibronectin type III module, and part of this region of approximately 200 amino acids has features typical of a cytokine receptor family. A cDNA-expressed gp130 showed no binding property to IL-6 or several other cytokines. Although a transfectant with an IL-6-R cDNA expressed mainly low affinity IL-6 binding sites, an increase in high affinity binding sites was observed after cotransfection with a gp130 cDNA. This confirmed that a gp130 is involved in the formation of high affinity IL-6 binding sites. A cloned gp130 could associate with a complex of IL-6 and soluble IL-6-R and transduce the growth signal when expressed in a murine IL-3-dependent cell line.
Amino Acid Sequence↗
Functional murine interleukin 6 receptor with the intracisternal A particle gene product at its cytoplasmic domain. Its possible role in plasmacytomagenesis.
Two species of the cDNAs encoding murine IL-6-R (one is abnormal and the other authentic) have been cloned from a plasmacytoma cell line, P3U1, and BALB/c mouse spleen cDNA libraries. In the cDNA encoding the abnormal IL-6-R, the region corresponding to an intracytoplasmic domain was replaced with a part of the long terminal repeat of the intracisternal A particle gene (IAP-LTR). The authentic IL-6-R consists of 460 amino acids with the domain of the Ig superfamily. The overall homology between murine and human IL-6-R was 69 and 54% at DNA and protein levels, respectively. The extracellular domain after the Ig-like domain of murine IL-6-R was found to have an homology with those of murine erythropoietin R, human IL-2-R beta chain, murine IL-4-R, and human granulocyte-macrophage CSF-R, as in the case of human IL-6-R, and these receptors have been classified as members of the IL receptor family. In P3U1 cells, the expression of the mRNA encoding abnormal IL-6-R was much higher than that of the mRNA encoding authentic IL-6-R. An IL-6-dependent human T cell line, KT-3, which did not respond to murine IL-6, acquired the responsiveness to murine IL-6 when transfected with the cDNA encoding abnormal IL-6-R, indicating that abnormal IL-6-R lacking a normal cytoplasmic domain can function. Since IL-6 functions as a potent growth factor for murine plasmacytomas, over-expression of abnormal IL-6-R may function as a positive selection element for the development of certain plasmacytomas.
Amino Acid Sequence↗
Interleukin 6 and its receptor in the immune response and hematopoiesis.
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 indicate that the IL-6R system consists of two polypeptide chains: one is an 80 kDa ligand-binding molecule and the other is a possible signal transducer, gp130.
Animals↗
Interleukin 6 (IL-6) and its receptor (IL-6R) in myeloma/plasmacytoma.
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Animals↗
Complex formation by bovine trypsin and a tetrapeptide (Leu-Arg-Pro-Gly-NH2): X-ray structure analysis of the complex in the orthorhombic crystal form with low molecular packing density.
The title tetrapeptide, Leu-Arg-Pro-Gly-NH2, forms a complex with trypsin in a novel orthorhombic crystal form with low molecular packing density. The complex formation was directly evidenced by X-ray crystallography. The crystal structure at 1.8 A resolution was refined to an R-factor of 20.5% for 13,923 reflection data, which were measured with synchrotron radiation. The tetrapeptide is bound to trypsin at the active site, and the binding mode is very similar to that of a bovine pancreatic trypsin inhibitor (BPTI):trypsin complex. The tetrapeptide:trypsin complex is the first observation that a peptide forms a stable complex with trypsin.
Amino Acid Sequence↗
Biological and clinical aspects of interleukin 6.
Interleukin 6 (IL-6) is a multi-functional cytokine that is produced by a range of cells and plays a central role in host defense mechanisms. Abnormal production of IL-6 has been suggested to be involved in glomerulonephritis, plasmacytomagenesis and in the pathogenesis of autoimmune diseases. In this review, Toshio Hirano and colleagues discuss the possible involvement of IL-6 in a variety of diseases, the regulatory mechanism(s) of expression of the IL-6 gene and the structure and function of the IL-6 receptor.
Acute-Phase Reaction↗
Immune and hematopoietic cell regulation: cytokines and their receptors.
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Amino Acid Sequence↗
Interleukin 6 and expression of its receptor on epidermal keratinocytes.
Interleukin 6 (IL 6) was detected in the culture supernatants of human epidermal keratinocytes and its production was enhanced by stimulation with cytokines. Production of IL 6 in keratinocytes was demonstrated directly by immunohistochemical staining of cultured cells with anti-IL 6 antibody. Keratinocyte-growth was increased by stimulation with recombinant IL 6 (as measured by either [3H] thymidine uptake or direct cell count). Moreover, expression of IL 6 receptor was demonstrated on monolayered cells, and the deeper cells of stratified keratinocytes in culture by immunohistochemistry. On the other hand, differentiated cells in the upper layers did not express IL 6 receptor on their surfaces, suggesting that the expression of IL 6 receptors may be confined to the proliferative cells. Thus, IL 6, which is produced by epidermal keratinocytes, may be involved in the regulation of normal keratinocyte growth.
Cell Division↗