Calmodulin mediates brain-derived neurotrophic factor cell survival signaling upstream of Akt kinase in embryonic neocortical neurons.
As a calcium-sensing protein, calmodulin acts as a transducer of the intracellular calcium signal for a variety of cellular responses. Although calcium is an important regulator of neuronal survival during development of the nervous system and is also implicated in the pathogenesis of neurodegenerative disorders, it is not known if calmodulin mediates these actions of calcium. To determine the role of calmodulin in regulating neuronal survival and death, we overexpressed calmodulin with mutations in all four Ca(2+)-binding sites (CaM(1-4)) or with disabled C-terminal Ca(2+)-binding sites (CaM(3,4)) in cultured neocortical neurons by adenoviral gene transfer. Long-term neuronal survival was decreased in neurons overexpressing CaM(1-4) and CaM(3,4), which could not be rescued by brain-derived neurotrophic factor (BDNF). The basal level of Akt kinase activation was decreased, and the ability of BDNF to activate Akt was completely abolished in neurons overexpressing CaM(1-4) or CaM(3,4). In contrast, BDNF-induced activation of p42/44 MAPKs was unaffected by calmodulin mutations. Treatment of neurons with calmodulin antagonists and a phosphatidylinositol 3-kinase inhibitor blocked the ability of BDNF to prevent neuronal death, whereas inhibitors of calcium/ calmodulin-dependent protein kinase II did not. Our findings demonstrate a pivotal role for calmodulin in survival signaling by BDNF in developing neocortical neurons by activating a transduction pathway involving phosphatidylinositol 3-kinase and Akt. In addition, our findings show that the C-terminal Ca(2+)-binding sites are critical for calmodulin-mediated cell survival signaling.
Cheng
Aiwu
A
Laboratories of Neurosciences and Cardiovascular Science, Gerontology Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
Wang
Shuqin
S
Yang
Dongmei
D
Xiao
Ruiping
R
Mattson
Mark P
MP
D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002470:Cell Survival; D053938:DNA Fragmentation; D004789:Enzyme Activation; D015151:Immunoblotting; D007150:Immunohistochemistry; D008858:Microscopy, Phase-Contrast; D020928:Mitogen-Activated Protein Kinases; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D019579:Neocortex / Q000196:embryology; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism
D019208:Brain-Derived Neurotrophic Factor; D002147:Calmodulin; D011518:Proto-Oncogene Proteins; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D001616:beta-Galactosidase; D002118:Calcium