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Received for publication October 11, 2007.
Revised December 22, 2007.
Accepted for publication January 17, 2008.
PKC Associated with
RACK: Cross-talk Between PKA and PKC Signaling Pathways
Previously we found that neural responses to ethanol and the dopamine D2 receptor (D2) agonist NPA involve both epsilon protein kinase C (
PKC) and cAMP-dependent protein kinase A (PKA). However, little is known about the mechanism underlying ethanol- and D2-mediated activation of
PKC and the relationship to PKA activation. In the present study, we used a new
PKC antibody, 14E6, that selectively recognizes active
PKC when not bound to its anchoring protein
RACK (receptor for activated C-kinase), and PKC isozyme-selective inhibitors and activators, to measure PKC translocation and catalytic activity. We show here that ethanol and NPA activated
PKC and also induced translocation of both
PKC and its anchoring protein,
RACK to a new cytosolic site. The selective
PKC agonist, pseudo-
RACK, activated
PKC but did not cause translocation of the
PKC/
RACK complex to the cytosol. These data suggest a step-wise activation and translocation of
PKC following NPA or ethanol treatment where
PKC first translocates and binds to its RACK and subsequently the
PKC/
RACK complex translocates to a new subcellular site. Direct activation of PKA by Sp-cAMPS, PGE1 or the adenosine A2A receptor is sufficient to cause
PKC translocation to the cytosolic compartment in a process that is dependent on PLC activation and requires PKA activity. These data demonstrate a novel cross-talk mechanism between
PKC and PKA signaling systems. PKA and PKC signaling have been implicated in alcohol rewarding properties in the mesolimbic dopamine system. Cross-talk between PKA and PKC may underlie some of the behaviors associated with alcoholism.
Key words:
Dopamine, Protein Kinase A, Protein Kinase C, Alcohols
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