p62 forms a ternary complex with PKCζ and PAR‐4 and antagonizes PAR‐4‐induced PKCζ inhibition

Abstract
It has been reported that prostate apoptosis response‐4 (PAR‐4) binds to and inhibits protein kinase Cζ (PKCζ) which phosphorylates IκB kinase β (IKKβ) for nuclear factor κB (NFκB) activation, while p62 binds to and recruits PKCζ to the NFκB signaling complex. Thus, a mechanism to coordinate the two binding proteins for the regulation of PKCζ is expected to exist. The present data show that p62 and PAR‐4 do not compete for PKCζ binding but directly interact each other and form a ternary complex with PKCζ. Furthermore, p62 not only enhances the catalytic activity of PKCζ but also reactivates catalytically inactive PAR‐4‐bound PKCζ. As the result, over‐expression of p62 protects cells from PAR‐4‐mediated inactivation of NFκB and apoptotic death. Thus, the regulatory role of p62 for free and PAR‐4‐bound PKCζ is important in activation of NFκB.