Wnt-1 induces growth, cytosolic beta-catenin, and Tcf/Lef transcriptional activation in Rat-1 fibroblasts.
Genetic evidence suggests that regulation of beta-catenin and regulation of Tcf/Lef family transcription factors are downstream events of the Wnt signal transduction pathway. However, a direct link between Wnt activity and Tcf/Lef transcriptional activation has yet to be established. In this study, we show that Wnt-1 induces a growth response in a cultured mammalian cell line, Rat-1 fibroblasts. Wnt-1 induces serum-independent cellular proliferation of Rat-1 fibroblasts and changes in morphology. Rat-1 cells stably expressing Wnt-1 (Rat-1/Wnt-1) show a constitutive up-regulation of cytosolic beta-catenin, while membrane-associated beta-catenin remains unaffected. Induction of cytosolic beta-catenin in Rat-1/Wnt-1 cells is correlated with activation of a Tcf-responsive transcriptional element. We thus provide evidence that Wnt-1 induces Tcf/Lef transcriptional activation in a mammalian system. Expression of a mutant beta-catenin (beta-CatS37A) in Rat-1 cells does not result in a proliferative response or a detectable change in the cytosolic beta-catenin protein level. However, beta-CatS37A expression in Rat-1 cells results in strong Tcf/Lef transcriptional activation, comparable to that seen in Wnt-1-expressing cells. These results suggest that Wnt-1 induction of cytosolic beta-catenin may have functions in addition to Tcf/Lef transcriptional activation.
Young
C S
CS
Department of Pathology and Center for Reproductive Sciences, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Kitamura
M
M
Hardy
S
S
Kitajewski
J
J
D000818:Animals; D002453:Cell Cycle; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D015972:Gene Expression Regulation, Neoplastic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D015534:Trans-Activators; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
C495268:Ctnnb1 protein, rat; D016895:Culture Media, Serum-Free; D003598:Cytoskeletal Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495245:Wnt1 protein, rat; D029961:Zebrafish Proteins; D051176:beta Catenin