The conserved polarity effector proteins PAR-3， PAR-6， CDC-42， and atypical protein kinase C (aPKC) form a core unit of the PAR protein network， which plays a central role in polarizing a broad range of animal cell types. To functionally polarize cells， these proteins must activate aPKC within a spatially defined membrane domain on one side of the cell in?response to symmetry-breaking cues. Using the Caenorhabditis elegans zygote as a model， we find that the localization and activation of aPKC involve distinct， specialized aPKC-containing assemblies: a PAR-3-dependent assembly that responds to polarity cues and promotes efficient segregation of aPKC toward the anterior but holds aPKC in an inactive state， and a CDC-42-dependent assembly in which aPKC is?active but poorly segregated. Cycling of aPKC between these distinct functional assemblies， which appears to depend on aPKC activity， effectively links?cue-sensing and effector roles within the PAR network to ensure robust establishment of polarity.