Phosphorylation of frizzled-3

Area of Science:

• Molecular Biology
• Developmental Biology
• Cell Signaling

Background:

• Wnt proteins are crucial secreted signaling molecules involved in numerous biological processes.
• Frizzled genes encode Wnt receptors that mediate intracellular signaling via the Disheveled protein.
• Biochemical regulation of Frizzled receptors remains incompletely understood.

Purpose of the Study:

• To investigate the biochemical regulation of Xenopus Frizzled-3.
• To determine the role of Disheveled in Frizzled-3 phosphorylation.
• To elucidate the functional consequences of Frizzled-3 phosphorylation on Wnt signaling.

Main Methods:

• Xenopus oocyte expression system.
• Site-directed mutagenesis of Frizzled-3 and Disheveled.
• Analysis of protein phosphorylation via electrophoretic mobility shifts.
• Assessment of Wnt signaling activity through neural crest marker induction.

Main Results:

• Xenopus Frizzled-3 is phosphorylated in a Disheveled-dependent manner, requiring the Disheveled DEP domain.
• Phosphorylation of serine 576 decreases electrophoretic mobility and represents a major phosphorylation site.
• Mutations impairing Frizzled-3 function also affect its phosphorylation.
• Mutation of C-terminal serines, including S576, enhances Frizzled-3-mediated neural crest marker induction.

Conclusions:

• Disheveled-dependent phosphorylation of Xenopus Frizzled-3 regulates its signaling activity.
• C-terminal phosphorylation, particularly at serine 576, acts as a negative regulator of Frizzled-3 signaling.
• These findings provide biochemical insights into Wnt receptor regulation.