Wnt signaling controls the phosphorylation status of beta-catenin.
At the heart of the canonical Wnt signaling cascade, adenomatous polyposis coli (APC), axin, and GSK3 constitute the so-called destruction complex, which controls the stability of beta-catenin. It is generally believed that four conserved Ser/Thr residues in the N terminus of beta-catenin are the pivotal targets for the constitutively active serine kinase GSK3. In cells that do not receive Wnt signals, glycogen synthase kinase (GSK) is presumed to phosphorylate beta-catenin, thus marking the latter for proteasomal degradation. Wnt signaling inhibits GSK3 activity. As a consequence, beta-catenin would no longer be phosphorylated and accumulate to form nuclear complexes with TCF/LEF factors. Although mutations in or near the N-terminal Ser/Thr residues stabilize beta-catenin in several types of cancer, the hypothesis that Wnt signaling controls phosphorylation of these residues remains unproven. We have generated a monoclonal antibody that recognizes an epitope containing two of the four residues when both are not phosphorylated. The epitope is generated upon Wnt signaling as well as upon pharmacological inhibition of GSK3 by lithium, providing formal proof for the regulated phosphorylation of the Ser/Thr residues of beta-catenin by Wnt signaling. Immunohistochemical analysis of mouse embryos utilizing the antibody visualizes sites that transduce Wnt signals through the canonical Wnt cascade.
van Noort
Mascha
M
Department of Immunology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Meeldijk
Jan
J
van der Zee
Ruurd
R
Destree
Olivier
O
Clevers
Hans
H
D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017354:Point Mutation; D011247:Pregnancy; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013329:Structure-Activity Relationship; D013912:Threonine / Q000378:metabolism; D015534:Trans-Activators; D014162:Transfection; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
D000911:Antibodies, Monoclonal; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; D013912:Threonine; D012694:Serine; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3