Mouse Embryonic Fibroblasts lacking the NHERF1 gene undergo cell transformation and down regulation of the Beta-Catenin-E-Cadherin complexes

KREIMANN EL; MORALES FC; TAKAHASHI Y; MOLINA J; GEORGESCU MM

Snowbird Resort, Snowbird, Utah, USA

Conferencia; Wnt and beta-Catenin Signaling in Development and Disease (E1); 2006

Keystone Symposium

  NHERF1/EBP50 is an adaptor protein containing two PDZ domains and Ezrin-binding region that interact with proteins at the plasma membrane and regulate its interaction with the cell cytoskeleton, endocytic and signaling pathways. NHERF1 binds to the Ezrin-radixin-moesin (ERM) family of proteins (Reczek D et al., 1997), platelet derived growth factor receptor (PDGFR) (Maudsley et al., 2000) and b-catenin (Shibata et al., 2003), among other proteins. b-catenin associates with cadherins at the cell membrane but as a transcriptional regulator when the Wnt pathway is activated.  EBP50 interacts with the carboxy domain of b-catenin through it PDZ2 domain and the association of EBP50 with stabilized b-catenin promotes transcriptional transactivation (Shibata et al., 2003). However, the effect of the NHERF1 -b-catenin interaction in the formation and maintenance of the adherent junctions had not been studied. Furthermore, the role of NHERF1   in cell transformation is still unclear. We have generated the NHERF1 deficient mice in order to define the importance of NHERF1 protein in cell growth, cell transformation and assembly and stability of the adherent junctions.                  Mouse embryonic fibroblasts (MEFs) from the NHERF1 (-/-) and NHERF1 (+/+) littermates were isolated from E14 embryos.  No difference in proliferation between NHERF1 (-/-) and (+/+) was apparent, however, the NHERF1 (-/-) MEFs were capable of forming colonies in soft agar.  There was an increase in the cytoplasmic accumulation of b-catenin and a disruption of the interaction of b-catenin with its partner proteins. These findings showed that the lack of the NHERF1 function potentiates cell transformation and NHERF1 gene could act as a tumor suppressor gene.   Acknowledgments: The first author is a recipient of a postdoctoral training grant in Molecular Genetics of Cancer at The University of Texas, MD Anderson Cancer Center. NCI CA09299-25.   NHERF1/EBP50 is an adaptor protein containing two PDZ domains and Ezrin-binding region that interact with proteins at the plasma membrane and regulate its interaction with the cell cytoskeleton, endocytic and signaling pathways. NHERF1 binds to the Ezrin-radixin-moesin (ERM) family of proteins (Reczek D et al., 1997), platelet derived growth factor receptor (PDGFR) (Maudsley et al., 2000) and b-catenin (Shibata et al., 2003), among other proteins. b-catenin associates with cadherins at the cell membrane but as a transcriptional regulator when the Wnt pathway is activated.  EBP50 interacts with the carboxy domain of b-catenin through it PDZ2 domain and the association of EBP50 with stabilized b-catenin promotes transcriptional transactivation (Shibata et al., 2003). However, the effect of the NHERF1 -b-catenin interaction in the formation and maintenance of the adherent junctions had not been studied. Furthermore, the role of NHERF1   in cell transformation is still unclear. We have generated the NHERF1 deficient mice in order to define the importance of NHERF1 protein in cell growth, cell transformation and assembly and stability of the adherent junctions.                  Mouse embryonic fibroblasts (MEFs) from the NHERF1 (-/-) and NHERF1 (+/+) littermates were isolated from E14 embryos.  No difference in proliferation between NHERF1 (-/-) and (+/+) was apparent, however, the NHERF1 (-/-) MEFs were capable of forming colonies in soft agar.  There was an increase in the cytoplasmic accumulation of b-catenin and a disruption of the interaction of b-catenin with its partner proteins. These findings showed that the lack of the NHERF1 function potentiates cell transformation and NHERF1 gene could act as a tumor suppressor gene.   Acknowledgments: The first author is a recipient of a postdoctoral training grant in Molecular Genetics of Cancer at The University of Texas, MD Anderson Cancer Center. NCI CA09299-25.