Interaction between the transforming growth factor-beta type II receptor/Smad pathway and beta-catenin during transforming growth factor-beta1-mediated adherens junction disassembly.
The aim of the current study was to examine the influence of transforming growth factor (TGF)-beta 1 on proximal tubular epithelial cell-cell interaction, with particular emphasis on the regulation of adherens junction complex formation. Stimulation of the proximal tubular cell line HK-2 cells by TGF-beta 1 led to loss of cell-cell contact and disassembly of both adherens and tight junctional complexes. Adherens junction disassembly was associated with reduction of both Triton-soluble and Triton-insoluble E-cadherin, and an increase in detergent-soluble beta-catenin. Under these conditions, immunoprecipitation and Western analysis demonstrated decreased association of beta-catenin, both with E-cadherin, alpha-catenin, and the cell cytoskeleton. Confocal microscopy after immunostaining, showed decreased intensity of peripheral E-cadherin staining, and redistribution of beta-catenin expression to a perinuclear location. Tight junction disassembly was manifest by a reduction in the expression of Triton-soluble occludin and ZO-1 by Western analysis and their disassociation manifested by immunostaining and confocal microscopy. Loss of cell-cell contact and disassembly of adherens junctions were seen after addition of TGF-beta 1 to the basolateral aspect of the cells. Immunoprecipitation experiments demonstrated co-localization of E-cadherin, beta-catenin, and TGF-beta 1 RII in unstimulated cells. After TGF-beta 1 stimulation, the TGF-beta 1 RII no longer associated with either E-cadherin or beta-catenin. Dissociation of the adherens junction protein from the TGF-beta 1 receptor was associated with increased beta-catenin tyrosine phosphorylation and decreased threonine phosphorylation. Furthermore after receptor ligand binding, beta-catenin became associated with the TGF-beta 1-signaling molecules Smad3 and Smad4.
Tian
Ya Chung
YC
Institute of Nephrology, University of Wales College of Medicine, Heath Park, Cardiff, Wales.
Phillips
Aled Owain
AO
D022005:Adherens Junctions / Q000187:drug effects* / Q000378:metabolism; D002461:Cell Line, Transformed; D016764:Cell Polarity; D048429:Cell Size / Q000187:drug effects; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein; D051901:Smad4 Protein; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D051176:beta Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D018125:Receptors, Transforming Growth Factor beta; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; C508960:TGFB1 protein, human; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D051176:beta Catenin; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II