Unpaired protein activates the JAK-STAT pathway in the adjacent germ stem cells to specify their self-renewal

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#Unit 4. Cell Communication and Cell Signaling

“canonical” Wnt signaling uses a second TM protein, LRP that associates with Frizzled in a Wnt signal– dependent manner.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Homologs

LRP in vertebrates = Arrow in Drosophila

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

In the absence of Wnts,

“free” β-catenin are targeted for degradation by a cytosolic destruction complex that is held together by the tumor suppressor protein Axin.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

β-catenin Destruction Complex contains:

Tumor suppressor APC

Dvl protein

Constitutively active protein kinases GSK 3β and CK1

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#Unit 4. Cell Communication and Cell Signaling

Kinases CK1 and GSK3,

sequentially phosphorylate β-catenin at multiple serine and threonine residues

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

E3 βTrCP ubiquitin ligase then binds to two phosphorylated residues on β catenin, leading to ubiquitinylation and degradation in proteasomes.