The role of atypical protein kinase C in the control of cell polarity of neuroblasts and epithelia in Drosophila

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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 apical-basal polarity in epithelia and in neuroblasts, the stem cells of the central nervous system. We have recently shown that Baz directly binds to the Drosophila atypical isoform of protein kinase C (DaPKC) and that both proteins are mutually dependent on each other for correct apical localization. Loss-of-function mutants of DaPKC show loss of apical-basal polarity, multilayering of epithelia, mislocalization of cell fate determinants and abnormal spindle orientation in neuroblasts. Together, these data provide strong evidence for the existence of an evolutionarily conserved mechanism that controls apical-basal polarity in epithelia and neuronal stem cells. In the proposed project we want to investigate how DaPKC controls the establishment of polarity in neuroblasts and epithelia and whether the kinase activity of the DaPKC protein is functionally important. We will assay the function of several mutant versions of DaPKC generated by in vitro mutagenesis both in vivo using transgenic flies and in tissue culture. In addition, we want to identify interaction partners and phosphorylation targets of DaPKC by immunoaffinity chromatography, followed by mass spectrometry analysis.