Biochemical characterization of suramin as a selective inhibitor for the PKA-mediated phosphorylation of HBV core protein in vitro.
The inhibitory effect of suramin on the phosphorylation of GST-HBV core fusion protein (GST-Hcore) and two GST-Hcore fusion polypeptides (Hcore157B and Hcore164B) by two alpha-type cAMP-dependent protein kinases (PKAIalpha and PKAIIalpha) was biochemically investigated in vitro. It was found that (i) this phosphorylation was inhibited by suramin at a low concentration (IC(50)=approx. 10 nM); (ii) a relative high dose of suramin was required to inhibit an autophosphorylation of PKAIIalpha (IC(50)=approx. 0.7 muM) and the PKAIIalpha-mediated phosphorylation of histone H2B (IC(50)=approx. 0.4 muM); (iii) the PKAIIalpha-mediated phosphorylation of Hcore157B was more sensitive to suramin than the phosphorylation of Hcore157B by Ca(2+)-dependent protein kinase (PKC); and (iv) suramin had a high binding affinity for Hcore157B, but not for histone H2B in vitro. These results suggest that suramin selectively inhibits the PKA-mediated phosphorylation of HBV-CP through the direct binding in vitro of suramin to the Arg-rich C-terminal region (containing three potential phosphorylation sites for PKA) on HBV-CP.
Okabe
Motohito
M
Genetical Biochemistry, School of Allied Health Sciences, Kitasato University, Kitasato, Sagamihara, Japan.
Enomoto
Masato
M
Maeda
Haruki
H
Kuroki
Kazuyuki
K
Ohtsuki
Kenzo
K
D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D006515:Hepatitis B virus / Q000187:drug effects*; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013498:Suramin / Q000378:metabolism / Q000494:pharmacology*; D014758:Viral Core Proteins / Q000737:chemistry / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D014758:Viral Core Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D013498:Suramin; D017868:Cyclic AMP-Dependent Protein Kinases