Wnt5a regulates distinct signalling pathways by binding to Frizzled2

Area of Science:

• Cell Biology
• Molecular Biology
• Signal Transduction

Background:

• Wnt5a is a key regulator of diverse intracellular signaling pathways.
• The mechanisms underlying Wnt5a's pathway specificity remain incompletely understood.
• Receptor internalization is a known modulator of Wnt signaling.

Purpose of the Study:

• To investigate the role of Wnt receptor internalization in Wnt5a-mediated signaling specificity.
• To determine if Wnt5a utilizes distinct mechanisms for activating beta-catenin-independent and -dependent pathways.

Main Methods:

• Utilized Wnt5a knockout embryonic fibroblasts.
• Assessed Rac activation and LRP6 phosphorylation.
• Investigated Frizzled2 (Fz2) internalization via clathrin-mediated pathways.
• Performed in vitro and cell-based binding assays.

Main Results:

• Wnt5a activated Rac in a beta-catenin-independent manner, requiring Frizzled2 (Fz2) and Ror1/Ror2 receptors.
• Wnt5a-induced Fz2 internalization occurred via clathrin-dependent endocytosis, essential for Rac activation.
• Wnt5a inhibited Wnt3a-induced LRP6 phosphorylation and beta-catenin accumulation.
• Wnt5a competed with Wnt3a for Fz2 binding, inhibiting beta-catenin signaling independently of Fz2 internalization.

Conclusions:

• Wnt5a employs distinct mechanisms for pathway regulation.
• Receptor internalization is critical for Wnt5a's beta-catenin-independent signaling.
• Wnt5a inhibits beta-catenin pathways through Fz2 binding competition, independent of internalization.