Calcium promotes cell survival through CaM-K kinase activation of the protein-kinase-B pathway.
The protection against apoptosis provided by growth factors in several cell lines is due to stimulation of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway, which results in activation of protein kinase B (PKB; also known as c-Akt and Rac) and phosphorylation and sequestration to protein 14-3-3 of the proapoptotic Bcl-2-family member BAD. A modest increase in intracellular Ca2+ concentration also promotes survival of some cultured neurons through a pathway that requires calmodulin but is independent of PI(3)K and the MAP kinases. Here we report that Ca2+/calmodulin-dependent protein kinase kinase (CaM-KK) activates PKB directly, resulting in phosphorylation of BAD on serine residue 136 and the interaction of BAD with protein 14-3-3. Serum withdrawal induced a three- to fourfold increase in cell death of NG108 neuroblastoma cells, and this apoptosis was largely blocked by increasing the intracellular Ca2+ concentration with NMDA (N-methyl-D-aspartate) or KCl or by transfection with constitutively active CaM-KK. The effect of NMDA on cell survival was blocked by transfection with dominant-negative forms of CaM-KK or PKB. These results identify a Ca2+-triggered signalling cascade in which CaM-KK activates PKB, which in turn phosphorylates BAD and protects cells from apoptosis.
Yano
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S
Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Tokumitsu
H
H
Soderling
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TR
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002118:Calcium / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D003001:Cloning, Molecular; D004789:Enzyme Activation; D016296:Mutagenesis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D051025:bcl-Associated Death Protein
C494821:Bad protein, rat; D002352:Carrier Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D051025:bcl-Associated Death Protein; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium