Keratinocyte adherens junctions initiate nuclear signaling by translocation of plakoglobin from the membrane to the nucleus.
Because changes in cell-cell adhesion have profound effects on cellular behavior, we hypothesized a link between the adhesion and signaling functions of plakoglobin and beta-catenin. To investigate the existence of adherens-junction-mediated signaling, we used peroxovanadate to tyrosine phosphorylate plakoglobin and beta-catenin and to dissociate adherens junctions. The distribution of plakoglobin and beta-catenin was determined by immunofluorescence, western blot analysis, pulse-chase radiolabeling, and biochemical subcellular fractionation. Coimmunoprecipitation studies from nuclear fractions, gel-shift assays, and transient transfections with T cell factor (TCF)/lymphoid enhancer factor (LEF) optimized promoter reporter constructs were used to investigate the ability of plakoglobin and beta-catenin that had redistributed from the membrane to the nucleus to form functional transcriptional regulatory complexes with TCF/LEF family member transcription factors. Tyrosine phosphorylation of plakoglobin and beta-catenin resulted in their rapid translocation from the cell membrane to the nucleus. Nuclear translocation was associated with increased plakoglobin and decreased beta-catenin binding to nuclear TCF/LEF and downregulation of gene transcription from TCF/LEF reporter constructs. These results are consistent with a signaling pathway initiated by structural changes in the adherens junction in which adherens-junction-derived plakoglobin regulates nuclear transcription by antagonizing the binding of beta-catenin to TCF/LEF proteins.
Hu
Peiqi
P
Department of Dermatology, University of North Carolina--Chapel Hill, School of Medicine, Chapel Hill, North Carolina 27599-7287, USA.
Berkowitz
Paula
P
O'Keefe
Edward J
EJ
Rubenstein
David S
DS
D022005:Adherens Junctions / Q000502:physiology*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000502:physiology*; D046508:Culture Techniques; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051180:Desmoplakins; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051821:Lymphoid Enhancer-Binding Factor 1; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D051176:beta Catenin; D051185:gamma Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D051180:Desmoplakins; D051821:Lymphoid Enhancer-Binding Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D051176:beta Catenin; D051185:gamma Catenin; C069276:peroxovanadate; D014638:Vanadates; D014443:Tyrosine