Calmodulin-mediated activation of Akt regulates survival of c-Myc-overexpressing mouse mammary carcinoma cells.

Abstract

c-Myc-overexpressing mammary epithelial cells are proapoptotic; their survival is strongly promoted by epidermal growth factor (EGF). We now demonstrate that EGF-induced Akt activation and survival in transgenic mouse mammary tumor virus-c-Myc mouse mammary carcinoma cells are both calcium/calmodulin-dependent. Akt activation is abolished by the phospholipase C-gamma inhibitor U-73122, by the intracellular calcium chelator BAPTA-AM, and by the specific calmodulin antagonist W-7. These results implicate calcium/calmodulin in the activation of Akt in these cells. In addition, Akt activation by serum and insulin is also inhibited by W-7. EGF-induced and calcium/calmodulin-mediated Akt activation occurs in both tumorigenic and non-tumorigenic mouse and human mammary epithelial cells, independent of their overexpression of c-Myc. These results imply that calcium/calmodulin may be a common regulator of Akt activation, irrespective of upstream receptor activator, mammalian species, and transformation status in mammary epithelial cells. However, only c-Myc-overexpressing mouse mammary carcinoma cells (but not normal mouse mammary epithelial cells) undergo apoptosis in the presence of the calmodulin antagonist W-7, indicating the vital selective role of calmodulin for survival of these cells. Calcium/calmodulin-regulated Akt activation is mediated directly by neither calmodulin kinases nor phosphatidylinositol 3-kinase (PI-3 kinase). Pharmacological inhibitors of calmodulin kinase kinase and calmodulin kinases II and III do not inhibit EGF-induced Akt activation, and calmodulin antagonist W-7 does not inhibit phosphotyrosine-associated PI-3 kinase activation. Akt is, however, co-immunoprecipitated with calmodulin in an EGF-dependent manner, which is inhibited by calmodulin antagonist W-7. We conclude that calmodulin may serve a vital regulatory function to direct the localization of Akt to the plasma membrane for its activation by PI-3 kinase.

• Authors: Tushar B Deb, Christine M Coticchia, Robert B Dickson
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 279 Issue 37 Pg. 38903-11 (Sep 10 2004) ISSN: 0021-9258 [Print] United States
• PMID: 15247222 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Calmodulin
• Chelating Agents
• Enzyme Inhibitors
• Estrenes
• Phosphodiesterase Inhibitors
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-myc
• Pyrrolidinones
• Sulfonamides
• 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
• 1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester
• Egtazic Acid
• W 7
• AKT1 protein, human
• Protein Serine-Threonine Kinases
• Proto-Oncogene Proteins c-akt
• Type C Phospholipases
• Phospholipase C gamma

Topics

• Animals
• Apoptosis
• Blotting, Western
• Calmodulin (metabolism)
• Cell Line, Tumor
• Cell Survival
• Chelating Agents (pharmacology)
• Dose-Response Relationship, Drug
• Egtazic Acid (analogs & derivatives, pharmacology)
• Enzyme Inhibitors (pharmacology)
• Estrenes (pharmacology)
• Humans
• Mice
• Mice, Transgenic
• Models, Biological
• Neurons (metabolism)
• Phosphatidylinositol 3-Kinases (metabolism)
• Phosphodiesterase Inhibitors (pharmacology)
• Phospholipase C gamma
• Precipitin Tests
• Protein Serine-Threonine Kinases (metabolism)
• Protein Transport
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-akt
• Proto-Oncogene Proteins c-myc (metabolism)
• Pyrrolidinones (pharmacology)
• Signal Transduction
• Sulfonamides (pharmacology)
• Time Factors
• Type C Phospholipases (pharmacology)