Polybasic PSr is required for PM targeting of Drosophila aPKC. (A) PM localization of wild-type DaPKC::GFP and nonpolybasic DaPKC^KR8Q::GFP in Drosophila wild type and DaPKC^−/− mutant follicular epithelial cells. Asterisks indicate DaPKC^−/− mutant cells identified by the loss of Histon2A::RFP (His2A::RFP). Images are in cross-section view. (B) In Drosophila embryonic epithelial cells, PM localization of Par-6::GFP or DaPKC::GFP was lost under hypoxia (0.5% O₂) but recovered after posthypoxia reoxygenation. Images are in tangential view of the apical surface of embryonic epithelia. (C) Par-6::GFP showed acute and reversible loss of PM targeting under hypoxia in both wild-type and lgl^−/− mutant (marked by the loss of nuclear RFP) follicular epithelial cells. Note that in lgl^−/− mutant cells, Par-6 was no longer restricted to apical PM but localized to both apical and lateral PM. Images are in cross-section view. Scale bars: 5 µm.