The coatomer protein beta'-COP, a selective binding protein (RACK) for protein kinase C epsilon

Distinct subcellular localization of activated protein kinase C (PKC) isozymes is mediated by their binding to isozyme-specific RACKs (receptors for activated C-kinase), Our laboratory has previously isolated one such protein, RACK1, and demonstrated that this protein displays specificity for PKC beta. We have recently shown that at least part of the PKC epsilon RACK-binding site on PKC epsilon lies within the unique V1 region of this isozyme (Johnson, J. A., Gray, M. O., Chen, C.-H., and Mochly-Rosen, D. (1996) J. Biol, Chem. 271, 24962-24966), Here, we have used the PKC epsilon V1 region to clone a PKC epsilon-selective RACK, which was identified as the COPI coatomer protein, beta'-COP. Similar to RACK1, beta'-COP contains seven repeats of the WD40 motif and fulfills the criteria previously established for RACKs. Activated PKC epsilon colocalizes with beta'-COP in cardiac myocytes and binds to Golgi membranes in a beta'-COP-dependent manner, A role for PKC in control of secretion has been previously suggested, but this is the first report of direct protein/protein interaction of PKC epsilon with a protein involved in vesicular trafficking.