Abstract
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Ten
protein kinase C (PKC) isozymes play divergent roles in signal transduction.
Because of sequence similarities, it is particularly difficult to
generate isozyme-selective small molecule inhibitors. In order to
identify such a selective binder, we derived a pharmacophore model
from the peptide EAVSLKPT, a fragment of PKCε that inhibits
the interaction of PKCε and receptor for activated C-kinase
2 (RACK2). A database of 330 000 molecules was screened in
silico, leading to the discovery of a series of thienoquinolines that
disrupt the interaction of PKCε with RACK2 in vitro. The most
active molecule, N-(3-acetylphenyl)-9-amino-2,3-dihydro-1,4-dioxino[2,3-g]thieno[2,3-b]quinoline-8-carboxamide
(8), inhibited this interaction with a measured IC50 of 5.9 μM and the phosphorylation of downstream target
Elk-1 in HeLa cells with an IC50 of 11.2 μM. Compound 8 interfered with MARCKS phosphorylation and TPA-induced translocation
of PKCε (but not that of PKCδ) from the cytosol to the
membrane. The compound reduced the migration of HeLa cells into a
gap, reduced invasion through a reconstituted basement membrane matrix,
and inhibited angiogenesis in a chicken egg assay.
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