title: Characterization of the interaction of hypericin with protein kinase C in U-87 MG human glioma cells.
abstract: A fluorescence imaging technique was used to monitor intracellular localization of protein kinase C (PKC) in U-87 MG human glioma cells in the presence of hypericin (Hyp) and phorbol 12-myristate-13-acetate (PMA). It is shown that PKC localization, which reflects its activity, is influenced by Hyp and this influence is different from that observed for PMA which acts as PKC activator. Fluorescence binding experiments were used to determine the binding constants of Hyp to several isoforms of PKC. The obtained values of K(d)s (approximately 100 nM) suggest that Hyp binds with high affinity to PKC. Finally, molecular modeling was used to compare structural models of the interaction of C1B domain of PKC (PKC isoforms alpha, delta, gamma) with Hyp and our previously published model of the (C1B domain PKCgamma)/PMA complex. The influence of Hyp on PKC translocation in U-87 MG cells in comparison with PMA, colocalization fluorescence pattern of Hyp and PKC, the higher binding affinity of Hyp to PKC in comparison with known binding constants of phorbol esters, as well as the binding mode of Hyp and PMA to the C1B domain of PKC suggested by molecular modeling, support the idea that Hyp and PMA might competitively bind to the regulatory domain of PKC.
authors.affiliation: Department of Biophysics, University of PJ Safarik, Kosice, Slovak Republic.
authors.forename: Silvia
authors.initials: S
authors.lastname: Kocanova
authors.forename: Tekla
authors.initials: T
authors.lastname: Hornakova
authors.forename: Jozef
authors.initials: J
authors.lastname: Hritz
authors.forename: Daniel
authors.initials: D
authors.lastname: Jancura
authors.forename: Dusan
authors.initials: D
authors.lastname: Chorvat
authors.forename: Anton
authors.initials: A
authors.lastname: Mateasik
authors.forename: Jozef
authors.initials: J
authors.lastname: Ulicny
authors.forename: Matthieu
authors.initials: M
authors.lastname: Refregiers
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Maurizot
authors.forename: Pavol
authors.initials: P
authors.lastname: Miskovsky
mesh_terms: D000873:Anthracenes; D045744:Cell Line, Tumor; D005910:Glioma / Q000473:pathology*; D006801:Humans; D010569:Perylene / Q000031:analogs & derivatives* / Q000494:pharmacology; D011493:Protein Kinase C / Q000032:analysis / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000873:Anthracenes; D010569:Perylene; C004965:hypericin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate