Serine/threonine protein kinase which is required for apico-basal cell polarity in the germ line as well as in epithelial and neural precursor cells, for epithelial planar cell polarity and for cell proliferation. During oocyte development, required for the posterior translocation of oocyte specification factors and for the posterior establishment of the microtubule organizing center within the presumptive oocyte. Phosphorylates l(2)gl which restricts l(2)gl activity to the oocyte posterior and regulates posterior enrichment of par-1, leading to establishment of correct oocyte polarity. Essential for apical localization of l(2)gl and par-6 in neuroblasts and for exclusion of mira from the apical cortex. Phosphorylates baz which is required for targeting of baz to the postsynaptic region where it is involved in actin organization, and for apical exclusion of baz which is necessary for establishment of the apical/lateral border in epithelial cells. Phosphorylates yrt which prevents its premature apical localization and is necessary for correct epithelial cell polarization. Required for the establishment of mitotic spindle orientation during symmetric division of epithelial cells and for apical exclusion of raps/Pins. Involved in symmetric adherens junction positioning during embryogenesis. Required for polarization of the spermatid cyst which is necessary for sperm differentiation. Required for stimulation of the Toll signaling pathway which activates Dif and dl and plays a role in innate immunity. Plays a role in memory enhancement. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with baz; the interaction is required for apical localization of aPKC in neuroblasts and epithelial cells. Interacts with Dap160; the interaction promotes aPKC apical localization and kinase activity. Interacts with and phosphorylates l(2)gl and yrt. Interacts with crb and ref(2)P. Forms a complex with baz, fz and Patj. Cytoplasmic at interphase but localizes to the apical cell cortex during mitosis. Expressed in the testis. In spermatid cysts, localizes near the tips of spermatid flagellar axonemes (at protein level). Detectable in freshly laid eggs before onset of zygotic transcription so is deposited in the egg during oogenesis. At the cellular blastoderm stage, present in all cells except the pole cells. During gastrulation, strongly expressed in tissues undergoing morphogenetic movements such as invaginating mesoderm, proctodeum and cephalic furrow. Strongly expressed in neuroblasts. Zygotes survive to mid-larval stages where they exhibit defects in neuroblast and epithelial cell polarity. Mutant neuroblasts lack apical localization of l(2)gl and par-6, and fail to exclude mira from the apical cortex. Oocytes do not differentiate and display failure of BicD and ORB to translocate from the anterior to the posterior crescent, accumulation of Dhc64C in the two posterior-most presumptive pre-oocytes instead of in a single cell as normal, and defective posterior assembly of the microtubule organizing center. Adherens junctions form atypical planar-polarized puncta at gastrulation. Reduced yrt phosphorylation. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. PKC subfamily.