Coordinated movement of RACK1 with activated beta IIPKC

Protein kinase C (PKC) isozymes move upon activation from one intracellular site to another. PKC-binding proteins, such as receptors for activated C k inase (RACKs), play an important role in regulating the localization and di verse functions of PKC isozymes. RACK1, the receptor for activated beta IIP KC, determines the localization and functional activity of beta IIPKC. Howe ver, the mechanism by which RACK1 localizes activated beta IIPKC is not kno wn. Here, we provide evidence that the intracellular localization of RACK1 changes in response to PKC activation. In Chinese hamster ovary cells trans fected with the dopamine D2L receptor and in NG108-15 cells, PKC activation by either phorbol ester or a dopamine D2 receptor agonist caused the movem ent of RACK1. Moreover, PKC activation resulted in the in situ association and movement of RACK1 and beta IIPKC to the same intracellular sites. Time course studies indicate that PKC activation induces the association of the two proteins prior to their co-movement. We further show that association o f RACK1 and beta IIPKC is required for the movement of both proteins. Our r esults suggest that RACK1 is a PKC shuttling protein that moves beta IIPKC from one intracellular site to another.