The hepatic interleukin-6 receptor. Studies on its structure and regulation by phorbol 12-myristate 13-acetate-dexamethasone.

摘要: Recombinant human 125I-interleukin-6 (IL-6) was cross-linked with the homobifunctional reagent disuccinimidyl suberate to hepatoma cells (HepG2). Three recombinant 125I-IL-6-containing complexes of apparent molecular masses 100, 120, and 200 kDa were immunoprecipitated specific antibodies IL-6 or 80-kDa receptor subunit. We show by immunoprecipitation, peptide mapping, use a cleavable heterobifunctional cross-linker (Denny-Jaffe reagent) that different polypeptides are involved in formation 100- 120-kDa IL-6-containing complexes. The compositions identified. 100-kDa complex consisted one ligand subunit, glycoprotein 80 (gp80), whereas found be composed polypeptide which immunoprecipitable monoclonal antibody AM64 directed against gp130. Exposure HepG2 phorbol 12-myristate 13-acetate (PMA) PMA-dexamethasone led an increase mRNA functional protein. Whereas treatment PMA gp80.gp130.IL-6 determined cross-linking, no corresponding high affinity binding sites found. existence third subunit present limiting amounts on is proposed explain this discrepancy. Evidence presented up-regulation caused depletion protein kinase C since inhibitor staurosporine mimics effect PMA-dexamethasone.