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Characterization of the Interaction of Hypericin with Protein Kinase C in U‐87 MG Human Glioma Cells
Author(s) -
Kocanova Silvia,
Hornakova Tekla,
Hritz Jozef,
Jancura Daniel,
Chorvat Dusan,
Mateasik Anton,
Ulicny Jozef,
Refregiers Matthieu,
Maurizot JeanClaude,
Miskovsky Pavol
Publication year - 2006
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2005-09-26-ra-696
Subject(s) - protein kinase c , hypericin , colocalization , phorbol , activator (genetics) , gene isoform , chemistry , biophysics , binding site , microbiology and biotechnology , biochemistry , receptor , enzyme , biology , endocrinology , gene
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 (∼100 n M ) 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 α, δ, γ) with Hyp and our previously published model of the (C1B domain PKCγ)/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.