Role of small GTP binding proteins in the growth-promoting and antiapoptotic actions of gastrin.
G17 has growth promoting and antiapoptotic effects on the AR4-2J pancreatic acinar cell line. We previously reported that whereas MAPK regulates G17-stimulation of AR4-2J cell proliferation, Akt mediates the antiapoptotic action of G17. We examined the signal-transduction pathways mediating G17 stimulation of AR4-2J cell growth and survival. G17 activated the small GTP binding proteins Ras, Rac, Rho, and Cdc42. Transduction of the cells with adenoviral vectors expressing dominant negative Akt, Ras, Rho, and Cdc42 but not dominant negative Rac inhibited AR4-2J cell proliferation and survival. Both exoenzyme C3 from Clostridium botulinum (C3), a toxin known to inactivate Rho, and PD98059, a MAPK inhibitor, reversed G17 inhibition of AR4-2J cell apoptosis. G17 induction of Akt activation was reduced by >60% by both dominant negative Ras and Rho and by 30% by dominant negative Cdc42. In contrast, G17-stimulated MAPK activation was blocked by >80% by dominant negative Ras but not by dominant negative Rho and Cdc42. Similar results were observed in the presence of C3. Dominant negative Rac failed to affect G17 induction of both Akt and MAPK, whereas it inhibited sorbitol by almost 50% but not G17-stimulated activation of p38 kinase. Thus G17 promotes AR4-2J cell growth and survival through the activation of multiple GTP binding proteins, which, in turn, regulate different protein kinase cascades. Whereas Ras activates Akt and MAPK, Rho and Cdc42 appear to regulate Akt and possibly other as yet unidentified kinases mediating the growth-stimulatory actions of G17.
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0682, USA.
Vinzenz
V
Stepan
Saravanan
S
Ramamoorthy
Nonthalee
N
Pausawasdi
Craig D
CD
Logsdon
Frederick K
FK
Askari
Andrea
A
Todisco
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D005755:Gastrins / Q000502:physiology*; D006133:Growth Substances / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology; D020287:In Situ Nick-End Labeling; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D010957:Plasmids / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051381:Rats; D013936:Thymidine / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000502:physiology; D020744:rac GTP-Binding Proteins / Q000502:physiology; D018631:ras Proteins / Q000502:physiology; D020741:rho GTP-Binding Proteins / Q000502:physiology
D005755:Gastrins; D006133:Growth Substances; D018398:Homeodomain Proteins; D011518:Proto-Oncogene Proteins; D000246:Adenosine Diphosphate Ribose; D019950:Mitogen-Activated Protein Kinase 1; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D013936:Thymidine