Interleukin-6 N-terminal peptides modulate the expression of junB protooncogene and the production of fibrinogen in HepG2 cells.
Interleukin-6 (IL-6) is a helical cytokine exerting pleiotropic activities including the regulation of hematopoiesis, B cell activation and acute-phase reaction. The structure-function relationship of the molecule is the subject of intensive investigation using point and deletion mutants. Our objective was to analyse the role of the N-terminal 18-46 region in IL-6-mediated expression of junB protooncogene and fibrinogen production, reflecting the acute phase response, with synthetic overlapping peptides. mRNA expression of junB was monitored by competitive RT-PCR, while sandwich ELISA was used for the detection of fibrinogen in the supernatant of HepG2 human hepatoma cells. We found that even short synthetic octapeptides can be stimulatory (in the absence of IL-6) or inhibitory (in the presence of IL-6) in both assays. To establish the molecular mechanism by which synthetic peptides exert their biological effects electromobility shift assay was carried out using HepG2 nuclear extracts. Peptides inducing junB expression initiate gel shifts of STAT3/DNA complexes, which may indicate the involvement of this signal transduction pathway. Circular dicroism spectroscopy data suggest that 8-11-mer peptides representing different parts of the 18-46 region have a marked tendency to adopt ordered conformations in a water/trifluoroethanol (1:1 v/v) mixture. Competition studies with rhIL-6 and selected fluorophore-labelled peptides indicate the presence of more than one binding site on soluble IL-6 receptor. Considering the possible multiple etiologic role of IL-6 in the pathogenesis of various diseases, these peptides could be useful for dissection of IL-6 related biological effects.
Bosze
Szilvia
S
Research Group of Peptide Chemistry, Hungarian Academy of Sciences, Eötvös L. University, P.O. Box 32, H-1518 Budapest 112, Hungary
Hudecz
Ferenc
F
Igaz
Péter
P
Ortutay
Zsuzsanna
Z
Csík
Gabriella
G
Falus
András
A
Tóth
Sára
S
D001667:Binding, Competitive; D004797:Enzyme-Linked Immunosorbent Assay; D005340:Fibrinogen / Q000096:biosynthesis*; D006801:Humans; D015850:Interleukin-6 / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D015850:Interleukin-6; D010446:Peptide Fragments; D016755:Proto-Oncogene Proteins c-jun; D005340:Fibrinogen