Manipulating JNK Signaling
with (−)-Zuonin
A
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Abstract
Recently, in a virtual screening strategy to identify
new compounds
targeting the D-recruitment site (DRS) of the c-Jun N-terminal kinases
(JNKs), we identified the natural product (−)-zuonin A. Here
we report the asymmetric synthesis of (−)-zuonin A and its
enantiomer (+)-zuonin A. A kinetic analysis for the inhibition of
c-Jun phosphorylation by (−)-zuonin A revealed a mechanism
of partial competitive inhibition. Its binding is proposed to weaken
the interaction of c-Jun to JNK by approximately 5-fold, without affecting
the efficiency of phosphorylation within the complex. (−)-Zuonin
A inhibits the ability of both MKK4 and MKK7 to phosphorylate and
activate JNK. The binding site of (−)-zuonin A is predicted
by docking and molecular dynamics simulation to be located in the
DRS of JNK. (+)-Zuonin A also binds JNK but barely impedes the binding
of c-Jun. (−)-Zuonin A inhibits the activation of JNK, as well
as the phosphorylation of c-Jun in anisomycin-treated HEK293 cells,
with the inhibition of JNK activation being more pronounced. (−)-Zuonin
A also inhibits events associated with constitutive JNK2 activity,
including c-Jun phosphorylation, basal Akt activation, and MDA-MB-231
cell migration. Mutations in the predicted binding site for (−)-zuonin
A can render it significantly more or less sensitive to inhibition
than wild type JNK2, allowing for the design of potential chemical
genetic experiments. These studies suggest that the biological activity
reported for other lignans, such as saucerneol F and zuonin B, may
be the result of their ability to impede protein–protein interactions
within MAPK cascades