title: Potentiation by thyroxine of interferon-gamma-induced HLA-DR expression is protein kinase A- and C-dependent.
abstract: L-Thyroxine (T4) and 3,3',5-L-triiodothyronine (T3) potentiate the antiviral state induced by interferon-gamma(IFN-gamma) in homologous cells by a mechanism that is dependent upon calcium/phospholipid-dependent protein kinase (PKC). L-T4 and T3 also potentiate induction by IFN-gamma of MHC class II HLA-DR antigen expression in HeLa cells. In the present studies of HLA-DR expression, the PKC inhibitor staurosporine (0.1-1 nM) enhanced the expression of HLA-DR when the inhibitor was added simultaneously with IFN-gamma, 100 IU/ml. In the presence of IFN-gamma and 10(-7) M T4, the same concentrations of staurosporine inhibited potentiation of HLA-DR expression by thyroid hormone. A more specific PKC inhibitor, CGP41251 (0.5-5 nM), similarly enhanced HLA-DR expression in the presence of IFN-gamma but inhibited thyroid hormone potentiation of antigen expression. Both actions of CGP41251 were suppressed when cells were also treated with phorbol 12-myristate 13-acetate (PMA). A phospholipase C inhibitor, U73122 (1-1000 nM), did not alter the potentiating ability of T4, although it inhibited in a concentration-dependent manner the expression of HLA-DR induced by IFN-gamma. The potentiating effect of T4 was much more sensitive to a cyclic AMP-dependent protein kinase (PKA) inhibitor,KT5720 (1-1000nM), than was the induction of HLA-DR by IFN-gamma. The inhibitory effects of KT5720 were reversed by concurrent 8-bromo-cAMP treatment. The calmodulin antagonist W-7 (5-50 microM) did not alter IFN-gamma induction of HLA-DR in either the presence or absence of T4. HLA-DR expression in HeLa cells appears to be under PKC-associated inhibition; IFN-gamma reverses this inhibition to promote the appearance of the DR antigen. In contrast, potentiation by T4 of induction of HLA-DR by IFN-gamma requires activation of PKC. PKA is involved both in DR induction by IFN-gamma and in potentiation of the latter by T4. Thus, PKA and PKC have discrete roles in IFN-gamma-induced MHC class II antigen expression and its modulation by thyroid hormone.
authors.affiliation: Department of Medicine, Albany Medical College, NY 12208, USA.
authors.forename: H Y
authors.initials: HY
authors.lastname: Lin
authors.forename: H R
authors.initials: HR
authors.lastname: Thacore
authors.forename: F B
authors.initials: FB
authors.lastname: Davis
authors.forename: L J
authors.initials: LJ
authors.lastname: Martino
authors.forename: P J
authors.initials: PJ
authors.lastname: Davis
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D002147:Calmodulin / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004357:Drug Synergism; D006684:HLA-DR Antigens / Q000096:biosynthesis*; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D011493:Protein Kinase C / Q000502:physiology*; D011994:Recombinant Proteins; D013974:Thyroxine / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D000998:Antiviral Agents; D002147:Calmodulin; D006684:HLA-DR Antigens; D011994:Recombinant Proteins; D007371:Interferon-gamma; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013974:Thyroxine