The ratio of red light (R) to far-red light (FR) varies remarkably in different environments. This ratio can be defined as follows:

TLS Online TPP Program

#Id: 9960

#Unit 4. Cell Communication and Cell Signaling

Wnt proteins are modified by linkage of a monounsaturated fatty acid, palmitoleic acid, to a serine in the middle of the protein.

TLS Online TPP Program

#Id: 9961

#Unit 4. Cell Communication and Cell Signaling

Lipid modifications of Wnt are catalyzed by the 

O-acetyltransferase Porcupine.

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#Id: 9962

#Unit 4. Cell Communication and Cell Signaling

Principal signaling receptor is Frizzled (Fz), contains 

7 TM α helices.

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#Id: 9963

#Unit 4. Cell Communication and Cell Signaling

The palmitoleate attached to the Wnt protein binds to a specific site on the Fz extracellular domain and stabilizes the Wnt-Fz complex.

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#Id: 9964

#Unit 4. Cell Communication and Cell Signaling

Wnt signal transduction pathways classify into:

1. Canonical wnt pathway (β-catenin dependent)

2. Noncanonical wnt pathways (β-catenin independent)

TLS Online TPP Program

#Id: 9965

#Unit 4. Cell Communication and Cell Signaling

Noncanonical pathways can be divided into two types: 

1. The “planar cell polarity” pathway

2. The “Wnt/calcium” pathway