The lipophilicity of phorbol esters as a critical factor in determining the pattern of translocation of protein kinase C delta fused to green fluorescent protein

Our previous study showed differential subcellular localization of protein kinase C (PKC) delta by phorbol esters and related ligands, using a green f luorescent protein-tagged construct in living cells. Here we compared the a bilities of a series of symmetrically substituted phorbol 12,13-diesters to translocate PKC delta. In vitro, the derivatives bound to PBC with similar potencies but differed in rate of equilibration. In vivo, the phorbol dies ters with short, intermediate, and long chain fatty acids induced distinct patterns of translocation. Phorbol 12,13-dioctanoate and phorbol 12,13-nona noate, the intermediate derivatives and most potent tumor promoters, showed patterns of translocation typical of phorbol 12-myristate 13-acetate, with plasma membrane and subsequent nuclear membrane translocation. The more hy drophilic compounds (phorbol 12,13-dibutyrate and phorbol 12,13-dihexanoate ) induced a patchy distribution in the cytoplasm, more prominent nuclear me mbrane translocation, and little plasma membrane localization at all concen trations examined (100 nM to 10 mu M). The highly lipophilic derivatives, p horbol 12,13-didecanoate and phorbol 12,13-diundecanoate, at 1 mu M caused either plasma membrane translocation only or no translocation at incubation times up to 60 min. Our results indicate that Lipophilicity of phorbol est ers is a critical factor contributing to differential PKC delta localizatio n and thereby potentially to their different biological activities.