Hydrolysis of pyrophosphate makes phosphodiester bond a highly favorable reaction with a DG of –7 kcal/mol, which corresponds to an equilibrium constant (Keq) of 105.

TLS Online TPP Program

#Id: 9974

#Unit 4. Cell Communication and Cell Signaling

In the absence of Wnt,

TCF is associated with transcriptional repressor proteins Groucho (Gro) that inhibit gene transcription in nucleus

TLS Online TPP Program

#Id: 9975

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9976

#Unit 4. Cell Communication and Cell Signaling

Formation of the Wnt/Fz/LRP complex at the cell

surface causes the adaptor protein Dishevelled, to bind to Fz and Axin to bind to LRP, resulting destabilization and inactivation of the destruction complex

TLS Online TPP Program

#Id: 9977

#Unit 4. Cell Communication and Cell Signaling

Unphosphorylated β-catenin translocates to the nucleus.

TLS Online TPP Program

#Id: 9978

#Unit 4. Cell Communication and Cell Signaling

β-catenin binds to TCF to displace the Gro repressor and recruits co-activator proteins Pygo, LGS, to activate target gene expression.

TLS Online TPP Program

#Id: 9979

#Unit 4. Cell Communication and Cell Signaling

Active Wnt signaling leads to the secretion of Notum.