Confocal microscopy of fixed larval Drosophila CNS stained with antibodies to detect atypical Protein Kinase C

Recruitment of the Par complex protein atypical Protein Kinase C (aPKC) to
a specific membrane domain is a key step in the polarization of animal
cells. While numerous proteins and phospholipids interact with aPKC, how
these interactions cooperate to control its membrane recruitment has been
unknown. Here we identify aPKC’s C1 domain as a phospholipid interaction
module that targets aPKC to the membrane of Drosophila neural stem cells
(NSCs). The isolated C1 binds the NSC membrane in an unpolarized manner
during interphase and mitosis and is uniquely sufficient among aPKC
domains for targeting. Other domains, including the catalytic module and
those that bind the upstream regulators Par-6 and Bazooka, restrict C1’s
membrane targeting activity – spatially and temporally – to the apical NSC
membrane during mitosis. Our results suggest that aPKC polarity results
from cooperative activation of autoinhibited C1-mediated membrane binding
activity.