Rap1 and p38 MAPK mediate 8-chloro-cAMP-induced growth inhibition in mouse fibroblast DT cells.
8-Cl-cAMP, which is known to induce differentiation, growth inhibition, and apoptosis in various cancer cells, has been investigated as a putative anti-cancer drug. Previously, we reported that 8-Cl-cAMP and its metabolite 8-Cl-adenosine induce growth inhibition and apoptosis through p38 mitogen-activated protein kinase (MAPK) activation. To further investigate the signal mechanisms that regulate the cellular effects of 8-Cl-cAMP, we focused on a small GTPase Rap1 that is known to be involved in growth inhibition and reverse-transformation. 8-Cl-cAMP and 8-Cl-adenosine could increase Rap1 activity, which was blocked by ABT702-an adenosine kinase inhibitor. This suggests that 8-Cl-cAMP-induced Rap1 activation is also dependent on the metabolic degradation of 8-Cl-cAMP. Overexpression of a constitutively active mutant form of Rap1 (Rap1V12) attenuated cellular growth and soft-agar colony formation, which was basically the same effect as that observed with the 8-Cl-cAMP treatment. Furthermore, the Rap1V12 transfectant showed a high level of p38 MAPK activation. However, 8-Cl-cAMP-induced Rap1 activation was not diminished by SB203580, a p38 MAPK inhibitor, suggesting that Rap1 activation might act upstream of p38 MAPK activation during 8-Cl-cAMP-induced growth inhibition.
Ahn
Young-Ho
YH
School of Biological Sciences, and Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea.
Han
Jee Hae
JH
Hong
Seung Hwan
SH
D016475:3T3 Cells; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D007155:Immunologic Factors / Q000378:metabolism*; D051379:Mice; D015398:Signal Transduction / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
D000970:Antineoplastic Agents; D007155:Immunologic Factors; D015124:8-Bromo Cyclic Adenosine Monophosphate; C044258:8-chloro-cyclic adenosine monophosphate; D048051:p38 Mitogen-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins