title: Characterization of complement C3 as a glycyrrhizin (GL)-binding protein and the phosphorylation of C3alpha by CK-2, which is potently inhibited by GL and glycyrrhetinic acid in vitro.
abstract: The physiological interaction between glycyrrhizin (GL) and serum complement C3, and the inhibitory effects of GL, glycyrrhetinic acid (GA), and a GA derivative (oGA) on the phosphorylation of C3 by casein kinase 2 (CK-2), were investigated in vitro. C3 was found to be a GL-binding protein (gbP), because (i) of its high affinity for a GL-affinity HPLC column; and (ii) both GL and GA induce conformational changes in C3. At least four trypsin-resistant fragments (p30, p25, p18, and p15) were detected when the (32)P-labeled C3alpha was digested with trypsin in the presence of 100 micro M GA. Two of these (p25 and p15) were immuno-precipitated with anti-C3a serum. Furthermore, it was found that C3a contains GL-binding domains, because (i) C3a (anaphylatoxin) could be selectively purified from the synovial fluids of patients with rheumatoid arthritis by GL-affinity column chromatography (HPLC); and (ii) purified human C3a has a high affinity for a GL-affinity column. In addition, C3alpha (p115) of C3 was effectively phosphorylated by CK-2 in the presence of poly-Arg (a CK-2 activator) in vitro. This phosphorylation was completely inhibited by 10 micro M oGA, 30 micro M GA, or 100 micro M GL. Taken together, these results suggest that the GL-induced inhibition of the physiological activities of C3a and C3alpha may be involved in the anti-inflammatory effect of GL in vivo.
authors.affiliation: Genetical Biochemistry and Signal Biology, Graduate School of Medical Sciences, Kitasato University, 1-15-1 Kitasato, Sagamihara 228-8555, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Kawakami
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shimoyama
authors.forename: Kenzo
authors.initials: K
authors.lastname: Ohtsuki
mesh_terms: D001168:Arthritis; D001665:Binding Sites; D047390:Casein Kinase II; D003176:Complement C3 / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015926:Complement C3a / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006034:Glycyrrhetinic Acid / Q000494:pharmacology*; D006035:Glycyrrhiza / Q000737:chemistry; D019695:Glycyrrhizic Acid / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D013582:Synovial Fluid / Q000737:chemistry
chemical_list: D003176:Complement C3; D019695:Glycyrrhizic Acid; D015926:Complement C3a; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D006034:Glycyrrhetinic Acid