Dopamine and ethanol cause translocation of εPKC associated with εRACK:: Cross-talk between cAMP-dependent protein kinase A and protein kinase C signaling pathways

We found previously that neural responses to ethanol and the dopamine D2 receptor (D2) agonist 2,10,11-trihydroxy-N-propylnorapomorphine hydrobromide (NPA) involve both epsilon protein kinase C (epsilon PKC) and cAMP-dependent protein kinase A (PKA). However, little is known about the mechanism underlying ethanol- and D2-mediated activation of epsilon PKC and the relationship to PKA activation. In the present study, we used a new epsilon PKC antibody, 14E6, that selectively recognized active epsilon PKC when not bound to its anchoring protein epsilon 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 epsilon PKC and induced translocation of both epsilon PKC and its anchoring protein, epsilon RACK to a new cytosolic site. The selective epsilon PKC agonist, pseudo-epsilon RACK, activated epsilon PKC but did not cause translocation of the epsilon PKC/epsilon RACK complex to the cytosol. These data suggest a step-wise activation and translocation of epsilon PKC after NPA or ethanol treatment, where epsilon PKC first translocates and binds to its RACK and subsequently the epsilon PKC/epsilon RACK complex translocates to a new subcellular site. Direct activation of PKA by adenosine-3',5'-cyclic monophosphorothioate, Sp-isomer (Sp-cAMPS), prostaglandin E1, or the adenosine A2A receptor is sufficient to cause epsilon PKC translocation to the cytosolic compartment in a process that is dependent on PLC activation and requires PKA activity. These data demonstrate a novel crosstalk mechanism between epsilon PKC and PKA signaling systems. PKA and PKC signaling have been implicated in alcohol rewarding properties in the mesolimbic dopamine system. Crosstalk between PKA and PKC may underlie some of the behaviors associated with alcoholism.