The tumor suppressor proteins p53 and Rb act as guardians of the cell cycle.

TLS Online TPP Program

#Id: 9087

#Unit 4. Cell Communication and Cell Signaling

Association with ARF6 activates A1, which catalyzes the transfer of ADP-ribose from NAD to the critical Arg residue in the P loop of the  subunit of Gαs. 

TLS Online TPP Program

#Id: 9088

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 9089

#Unit 4. Cell Communication and Cell Signaling

ADP-ribosylation blocks the GTPase activity of Gαs and renders Gαs permanently active. 

TLS Online TPP Program

#Id: 9090

#Unit 4. Cell Communication and Cell Signaling

This results in continuous activation of the AC of intestinal epithelial cells, chronically active PKA which phosphorylates the CFTR Cl- channel and a Na-H exchanger in the intestinal epithelial cells. 

TLS Online TPP Program

#Id: 9091

#Unit 4. Cell Communication and Cell Signaling

The resultant efflux of NaCl triggers massive water loss through the intestine as cells respond to the ensuing osmotic imbalance causes severe dehydration and electrolyte loss.

TLS Online TPP Program

#Id: 9092

#Unit 4. Cell Communication and Cell Signaling

Pertussis toxin, produced by Bordetella pertussis, catalyzes ADP-ribosylation of the  subunit of Gαi, preventing GDP-GTP exchange and blocking inhibition of adenylyl cyclase.