Abstract 1051: Atypical PKC and TGFβ receptors co-operate to phosphorylate Par6

Abstract

Abstract Transforming growth factor beta (TGFβ) is involved in many aspects of cellular behavior including apoptosis and differentiation. In tumor cells, TGFβ signaling alters cell plasticity through a loss in apical-basal cell polarity and induces epithelial to mesenchymal transition (EMT). Integral to this process is the phosphorylation of a polarity protein, Par6, on a conserved serine residue (S345). Recent work has shown that phosphorylation of this site not only increases cell plasticity and EMT, but also promotes an invasive phenotype in breast cancer cells. Our work suggests that a polarity partner of Par6, atypical Protein Kinase C (aPKC), can also phosphorylate Par6 on this critical site to drive distinct cellular changes in non-small cell lung cancer (NSCLC) cells. Using co-immunoprecipitation studies and immunofluorescence microscopy, we show that aPKCι interacts with TGFβ receptors through the adaptor Par6, and that these proteins localize to the leading edge of migrating cells. Furthermore, co-expression of Par6 with TGFβ receptors results in increased phospho-Par6 levels as previously reported. However, we have also found that phosphorylation of Par6 increases in the presence of aPKC. aPKC kinase activity as well as association with Par6 were found to be important for Par6 phosphorylation as evidenced by a loss in phospho-Par6 using a kinase deficient mutant of PKCζ (PKCζ -KR) as well as a mutant of Par6 that does not bind aPKC (Par6-K19A). Furthermore, gene silencing of atypical PKC reduces TGFβ induced cell morphology changes, E-cadherin loss, and stress fiber production. Finally, gene silencing of atypical PKC was observed to reduce TGFβ dependent migration of NSCLC cells. In conclusion, our results indicate that atypical PKC cooperate with TGFβ receptors to regulate phospho-Par6 levels to drive an invasive phenotype of NSCLC cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1051. doi:10.1158/1538-7445.AM2011-1051