cPKC-dependent sequestration of membrane-recycling components in a subset of recycling endosomes

In addition to the classical role of protein kinase C (PKC) as a mediator of transmembrane signals initiated at the plasma membrane, there is also significant evidence to suggest that a more sustained PKC activity is necessary for a variety of long term cellular responses. To date, the subcellular localization of PKC during sustained activation has not been extensively studied. We report here that long term activation of PKC (1 h) leads to the selective translocation of classical PKC isoenzymes, alpha and betaII, to a juxtanuclear compartment. Juxtanuclear translocation of PKC required an intact C1 and C2 domain, and occurred in a microtubule-dependent manner. This juxtanuclear compartment was localized close to the Golgi complex but displayed no overlap with Golgi markers, and was resistant to dispersal with Golgi disrupting agents, brefeldin A and nocodazole. Further characterization revealed that PKCalpha and betaII translocated to a compartment that colocalized with the small GTPase, rab11, which is a marker for the subset of recycling endosomes concentrated around the microtubule-organizing center/centrosome. Analysis of the functional consequence of cPKC translocation on membrane recycling demonstrated a cPKC-dependent sequestration of transferrin, a marker of membrane recycling, in the cPKC compartment. These results identify a novel site for cPKC translocation and define a novel function for the sustained activation of PKCalpha and betaII in regulation of recycling components.