Dollo’s law: A biological generalization positing that complex characters, once lost in evolution, are extremely unlikely to reappear and thus the loss of complex characters is virtually always irreversible.

TLS Online TPP Program

#Id: 10538

#Unit 4. Cell Communication and Cell Signaling

In healthy cells, the Bcl-2 or Bcl-xL blocking the ability of Bak or Bax to oligomerize and form pores in the outer mitochondrial membrane.

TLS Online TPP Program

#Id: 10539

#Unit 4. Cell Communication and Cell Signaling

Trophic factors (NGF) leads to activation of receptor tyrosine kinases (TrkA) and activation of the protein kinase B pathway

TLS Online TPP Program

#Id: 10540

#Unit 4. Cell Communication and Cell Signaling

PKB phosphorylates Bad, and phosphorylated Bad forms a complex with a cytosolic 14-3-3 protein.

TLS Online TPP Program

#Id: 10541

#Unit 4. Cell Communication and Cell Signaling

In the absence of trophic factors, nonphosphorylated

Bad binds to Bcl-2, releasing Bax and Bak and allowing them to form oligomeric membrane pores and holes.

TLS Online TPP Program

#Id: 10542

#Unit 4. Cell Communication and Cell Signaling

DNA damage or UV irradiation leads to induction of synthesis of the BH3-only Puma protein which binds to Bak and Bax as well as to Bcl-2, allowing Bak and

Bax to form oligomeric pores.

TLS Online TPP Program

#Id: 10543

#Unit 4. Cell Communication and Cell Signaling

Removal of a cell from its substratum disrupts integrin signaling, leading to release of the BH3-only Bim

protein from the cytoskeleton which binds to Bak and Bax to promote pore formation.