Wnt/β-catenin signaling plays essential roles during development. The following statements are made about the Wnt/β-catenin signaling pathway:

A. In the absence of Wnt ligands, β-catenin is phosphorylated by the APC/Axin/GSK-3β complex, leading to its degradation.
B. The β-catenin/TCF complex acts as a repressor of gene expression upon activation of Wnt signaling.
C. The Wnt/β-catenin pathway is initiated by binding of Wnt ligands to receptor tyrosine kinases (RTKs).
D. β-catenin is involved in both cell-to-cell adhesion and transcriptional regulation.

Which one of the following options represents all correct statements?

Correct option is C

EXPLANATION-

Statement A - Correct. In the absence of Wnt ligands, β-catenin is targeted for phosphorylation by a destruction complex consisting of APC (Adenomatous Polyposis Coli), Axin, and GSK-3β (Glycogen Synthase Kinase 3 beta). This phosphorylation marks β-catenin for ubiquitination and subsequent proteasomal degradation, preventing its accumulation in the cytoplasm.

Statement B -  Incorrect. Upon activation of the Wnt signaling pathway, β-catenin accumulates and translocates to the nucleus, where it binds to TCF/LEF transcription factors to activate gene expression, not repress it.

Statement C -  Incorrect. The Wnt/β-catenin pathway is initiated by Wnt ligands binding to Frizzled receptors and LRP5/6 co-receptors, not receptor tyrosine kinases (RTKs).

Statement D -  Correct. β-catenin has dual roles: it functions at the plasma membrane in cell-to-cell adhesion by interacting with cadherins, and it also acts as a transcriptional co-activator in the nucleus regulating gene expression.

The correct answer is (c)  A and D only