Drosophila atypical protein kinase C associates with Bazooka and controls polarity of epithelia and neuroblasts

The establishment and maintenance of polarity is of fundamental importance for the function of epithelial and neuronal cells, In Drosophila, the multi -PDZ domain protein Bazooka (Baz) is required for establishment of apico-ba sal polarity in epithelia and in neuroblasts, the stem cells of the central nervous system, In the latter, Bat anchors Inscuteable in the apical cytoc ortex, which is essential for asymmetric localization of cell fate determin ants and for proper orientation of the mitotic spindle. Here we show that B at directly binds to the Drosophila atypical isoform of protein kinase C an d that both proteins are mutually dependent on each other for correct apica l localization. Loss-of-function mutants of the Drosophila atypical isoform of PKC show loss of apico-basal polarity, multilayering of epithelia, misl ocalization of Inscuteable and abnormal spindle orientation in neuroblasts, Together, these data provide strong evidence for the existence of an evolu tionary conserved mechanism that controls apico-basal polarity in epithelia and neuronal stem cells. This study is the first functional analysis of an atypical protein kinase C isoform using a loss-of-function allele in a gen etically tractable organism.