STUDIES ON THE STRUCTURE AND REGULATION OF THE HUMAN HEPATIC INTERLEUKIN-6 RECEPTOR

Affinity cross‐linking of 125I‐labeled recombinant human interleukin‐6 (IL‐6) to human hepatoma cells (HepG2) allowed the detection of three IL‐6‐containing complexes with molecular masses of 100 kDa, 120 kDa and 200 kDa. Treatment of HepG2 cells with dexamethasone led to a time‐ and dose‐dependent up‐regulation of IL‐6‐receptor mRNA levels. By the use of cross‐linking this effect was also seen at the protein level, where all three IL‐6‐binding complexes increased upon incubation of HepG2 cells with dexamethasone. Under conditions of IL‐6‐receptor up‐regulation by dexamethasone, γ‐fibrinogen mRNA induction by IL‐6 is stronger and occurs earlier than without dexamethasone. We propose therefore that the expression of the IL‐6 receptor might be a rate‐limiting step in acute‐phase‐protein induction. Copyright © 1990, Wiley Blackwell. All rights reserved