Department of Dermatology, University of North Carolina – Chapel Hill, School of Medicine, Chapel Hill, North Carolina, USA

Correspondence: David S. Rubenstein, Department of Dermatology, University of North Carolina – Chapel Hill, School of Medicine, Suite 3100 Thurston-Bowles Bldg CB 7287, Chapel Hill, NC 27599-7287; Email: druben@med.unc.edu

Received 13 November 2002; Revised 8 January 2003; Accepted 20 March 2003; Published online 23 July 2003.

Abstract

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 -catenin. To investigate the existence of adherens-junction-mediated signaling, we used peroxovanadate to tyrosine phosphorylate plakoglobin and -catenin and to dissociate adherens junctions. The distribution of plakoglobin and -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 -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 -catenin resulted in their rapid translocation from the cell membrane to the nucleus. Nuclear translocation was associated with increased plakoglobin and decreased -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 -catenin to TCF/LEF proteins.