Neuroprotection of immortalized hippocampal neurones by brain-derived neurotrophic factor and Raf-1 protein kinase: role of extracellular signal-regulated protein kinase and phosphatidylinositol 3-kinase.
We have investigated the molecular mechanisms of neurotrophin-mediated cell survival in HT22 cells, a murine cell line of hippocampal origin, expressing the brain-derived neurotrophic factor (BDNF) receptor TrkB as well as the TrkB.T1 splice variant. Stimulation with BDNF protected HT22-TrkB cells, but not HT22-TrkB.T1 cells, against programmed cell death induced by serum deprivation. BDNF did not, however, provide protection against oxidative glutamate toxicity, indicating that serum deprivation-induced cell death differs substantially from glutamate-induced cell death. Using a pharmacological strategy to block either the extracellular signal-regulated protein kinase (ERK) or the phosphatidylinositol 3-kinase (PI3) pathway, we show that activation of PI3 kinase is required for the neuroprotective activity of BDNF in HT22 cells. To further analyse the role of ERK in neuroprotection we expressed an inducible deltaRaf-1:ER fusion protein in HT22 cells. Activation of this conditionally active form of Raf-1 induced a sustained phosphorylation of ERK, and protected the cells from serum withdrawal-induced cell death. Inhibition of ERK activation at different time points revealed that a prolonged activation of ERK is essential to protect HT22 cells from cell death triggered by the withdrawal of serum, indicating that the duration of ERK activation is of major importance for its neuroprotective biological function.
Department of Medical Biochemistry and Molecular Biology, University of Saarland Medical Center, Homburg, Germany.
Oliver G
OG
Rössler
Klaus M
KM
Giehl
Gerald
G
Thiel
D017398:Alternative Splicing; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D051766:Early Growth Response Protein 1; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018014:Gene Transfer Techniques; D018698:Glutamic Acid / Q000633:toxicity; D006624:Hippocampus / Q000166:cytology; D017874:Immediate-Early Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism*; D020813:Receptor, trkB / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000096:biosynthesis
D019208:Brain-Derived Neurotrophic Factor; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; D004791:Enzyme Inhibitors; D018698:Glutamic Acid; D017874:Immediate-Early Proteins; D020928:Mitogen-Activated Protein Kinases; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019908:Proto-Oncogene Proteins c-raf; D020813:Receptor, trkB; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C486109:Egr1 protein, mouse