Isoenzyme-specific translocation of protein kinase C (PKC)betaII and not PKCbetaI to a juxtanuclear subset of recycling endosomes: involvement of phospholipase D.

Elucidation of isoenzyme-specific functions of individual protein kinase C (PKC) isoenzymes has emerged as an important goal in the study of this family of kinases, but this task has been complicated by modest substrate specificity and high homology among the individual members of each PKC subfamily. The classical PKCbetaI and PKCbetaII isoenzymes provide a unique opportunity because they are the alternatively spliced products of the beta gene and are 100% identical except for the last 50 of 52 amino acids. In this study, it is shown that green fluorescent protein-tagged PKCbetaII and not PKCbetaI translocates to a recently described juxtanuclear site of localization for PKCalpha and PKCbetaII isoenzymes that arises with sustained stimulation of PKC. Mechanistically, translocation of PKCbetaII to the juxtanuclear region required kinase activity. PKCbetaII, but not PKCbetaI, was found to activate phospholipase D within this time frame. Inhibitors of phospholipase D (1-butanol and a dominant negative construct) prevented the translocation of PKCbetaII to the juxtanuclear region but not to the plasma membrane, thus demonstrating a role for phospholipase D in the juxtanuclear translocation of PKCbetaII. Taken together, these results define specific biochemical and cellular actions of PKCbetaII when compared with PKCbetaI.