title: The designer cytokine hyper-interleukin-6 is a potent activator of STAT3-dependent gene transcription in vivo and in vitro.
abstract: Interleukin-6 (IL-6) triggers pivotal pathways in vivo. The designer protein hyper-IL-6 (H-IL-6) fuses the soluble IL-6 receptor (sIL-6R) through an intermediate linker with IL-6. The intracellular pathways that are triggered by H-IL-6 are not defined yet. Therefore, we studied the molecular mechanisms leading to H-IL-6-dependent gene activation. H-IL-6 stimulates haptoglobin mRNA expression in HepG2 cells, which is transcriptionally mediated as assessed by run-off experiments. The increase in haptoglobin gene transcription correlates with higher nuclear translocation of tyrosine-phosphorylated STAT3 and its DNA binding. As H-IL-6 stimulates STAT3-dependent gene transcription, we compared the molecular mechanism between IL-6 and H-IL-6. Transfection experiments were performed with a STAT3-dependent luciferase construct. The same amount of H-IL-6 stimulated luciferase activity faster, stronger, and for a longer period of time. Dose response experiments showed that a 10-fold lower dose of H-IL-6 stimulated STAT3-dependent gene transcription comparable with the higher amount of IL-6. Cotransfection with the gp80 and/or gp130 receptor revealed that the effect of H-IL-6 on STAT3-dependent gene transcription is restricted to the gp80/gp130 receptor ratio. High amounts of gp130 increased and high amounts of gp80 decreased the effect on H-IL-6-dependent gene transcription. To investigate the in vivo effect of H-IL-6 on gene transcription in the liver, H-IL-6 and IL-6 were injected into C3H mice. H-IL-6 was at least 10-fold more effective in stimulating the DNA binding and nuclear translocation of STAT3, which enhances haptoglobin mRNA and protein expression. Thus H-IL-6 stimulates STAT3-dependent gene transcription in liver cells in vitro and in vivo at least 10-fold more effectively than IL-6. Our results provide evidence that H-IL-6 is a promising designer protein for therapeutic intervention during different pathophysiological conditions also in humans.
authors.affiliation: Department of Gastroenterology and Hepatology, Medizinische Hochschule, Hannover, Federal Republic of Germany.
authors.forename: T
authors.initials: T
authors.lastname: Rakemann
authors.forename: M
authors.initials: M
authors.lastname: Niehof
authors.forename: S
authors.initials: S
authors.lastname: Kubicka
authors.forename: M
authors.initials: M
authors.lastname: Fischer
authors.forename: M P
authors.initials: MP
authors.lastname: Manns
authors.forename: S
authors.initials: S
authors.lastname: Rose-John
authors.forename: C
authors.initials: C
authors.lastname: Trautwein
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D050822:Cytokine Receptor gp130; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006242:Haptoglobins / Q000235:genetics; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D018123:Receptors, Interleukin / Q000378:metabolism*; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000494:pharmacology; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D004268:DNA-Binding Proteins; D006242:Haptoglobins; C494199:IL6ST protein, human; C494200:Il6st protein, mouse; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D019947:Receptors, Interleukin-6; D011993:Recombinant Fusion Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; C104543:interleukin 6-interleukin 6 receptor fusion protein, recombinant; C113250:interleukin-6 receptor alpha; D050822:Cytokine Receptor gp130; D014443:Tyrosine; D004247:DNA