The Journal of Neuroscience, April 25, 2007, 27(17):4562-4571; doi:10.1523/JNEUROSCI.5110-06.2007
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Neurobiology of Disease
Phosphatidylinositol 3-Akt-Kinase-Dependent Phosphorylation of p21Waf1/Cip1 as a Novel Mechanism of Neuroprotection by Glucocorticoids
Christoph Harms,1,2
Katharina Albrecht,3
Ulrike Harms,1
Kerstin Seidel,3
Ludger Hauck,4
Tina Baldinger,1,2
Denise Hübner,1,2
Golo Kronenberg,1,5
Junfeng An,4
Karsten Ruscher,1
Andreas Meisel,1
Ulrich Dirnagl,6
Rüdiger von Harsdorf,4
Matthias Endres,1,2 and
Heide Hörtnagl3
1Klinik und Poliklinik für Neurologie, 2Neurowissenschaftliches Forschungszentrum, and 3Institut für Pharmakologie und Toxikologie, Charité Campus Mitte, CharitéUniversitätsmedizin Berlin, D-10117 Berlin, Germany, 4Max Delbrück Center for Molecular Medicine, D-13125 Berlin, Germany, 5Klinik und Poliklinik für Psychiatrie, Charité Campus Benjamin Franklin, D-14050 Berlin, Germany, and 6Abteilung für Experimentelle Neurologie, CharitéUniversitätsmedizin Berlin, D-10117 Berlin, Germany
Correspondence should be addressed to either of the following: Dr. Matthias Endres, Klinik und Poliklinik für Neurologie, Charitéplatz 1, D-10117 Berlin, Germany, Email: matthias.endres{at}charite.de; or Dr. Heide Hörtnagl, Institut für Pharmakologie und Toxikologie, Charité, Dorotheenstrasse 94, D-10117 Berlin, Germany, Email: heide.hoertnagl{at}charite.de
The role of glucocorticoids in the regulation of apoptosis remains incongruous. Here, we demonstrate that corticosterone protects neurons from apoptosis by a mechanism involving the cyclin-dependent kinase inhibitor p21Waf1/Cip1. In primary cortical neurons, corticosterone leads to a dose- and Akt-kinase-dependent upregulation with enhanced phosphorylation and cytoplasmic appearance of p21Waf1/Cip1 at Thr 145. Exposure of neurons to the neurotoxin ethylcholine aziridinium (AF64A) results in activation of caspase-3 and a dramatic loss of p21Waf1/Cip1 preceding apoptosis in neurons. These effects of AF64A are reversed by pretreatment with corticosterone. Corticosterone-mediated upregulation of p21Waf1/Cip1 and neuroprotection are completely abolished by glucocorticoid and mineralocorticoid receptor antagonists as well as inhibitors of PI3- and Akt-kinase. Both germline and somatically induced p21Waf1/Cip1 deficiency abrogate the neuroprotection by corticosterone, whereas overexpression of p21Waf1/Cip1 suffices to protect neurons from apoptosis. We identify p21Waf1/Cip1 as a novel antiapoptotic factor for postmitotic neurons and implicate p21Waf1/Cip1 as the molecular target of neuroprotection by high-dose glucocorticoids.
Key words: apoptosis; neuroprotection; cortical neurons; p21Waf1/Cip1; glucocorticoid; Akt-kinase
Received July 19, 2006;
revised March 6, 2007;
accepted March 19, 2007.
Correspondence should be addressed to either of the following: Dr. Matthias Endres, Klinik und Poliklinik für Neurologie, Charitéplatz 1, D-10117 Berlin, Germany, Email: matthias.endres{at}charite.de; or Dr. Heide Hörtnagl, Institut für Pharmakologie und Toxikologie, Charité, Dorotheenstrasse 94, D-10117 Berlin, Germany, Email: heide.hoertnagl{at}charite.de