The coatomer protein β'-COP, a selective binding protein (RACK) for protein kinase Cε

Abstract

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 PKCβ. We have recently shown that at least part of the PKCε RACK-binding site on PKCε 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 PKCε V1 region to clone a PKCε- selective RACK, which was identified as the COPI coatomer protein, β'-COP. Similar to RACK1, β'-COP contains seven repeats of the WD40 motif and fulfills the criteria previously established for RACKs. Activated PKCε colocalizes with β'-COP in cardiac myocytes and binds to Golgi membranes in a β'-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 PKCε with a protein involved in vesicular trafficking.