A novel role for extracellular signal-regulated kinase 5 and myocyte enhancer factor 2 in medulloblastoma cell death.
Expression of the neurotrophin-3 receptor, tyrosine kinase C (TrkC), is associated with favorable prognosis in medulloblastoma patients. This may be due to increased tumor apoptosis induced by TrkC activation. Neurotrophin-3/TrkC-induced apoptosis is inhibited by the mitogen-activated protein (MAP) kinase (MAPK) pharmacologic antagonists SB203580 and PD98059. In addition to extracellular signal-regulated kinase (ERK)-1/2, PD98059 also inhibits the more recently identified neurotrophin-responsive MAPK, ERK5 (big MAPK 1). In the present study, we investigate the contribution of ERK5 and its target myocyte enhancer factor 2 (MEF2) to neurotrophin-3/TrkC-induced medulloblastoma cell death. Neurotrophin-3 not only enhanced ERK5 phosphorylation but also significantly enhanced the transcriptional activity of MEF2, a specific target of ERK5. Overexpression of both ERK5 and MEF2 induced a statistically significant increase in cell death of neurotrophin-3-responsive and nonresponsive medulloblastoma cell lines (Daoy-trkC and Daoy) and primary cultures of patched heterozygous mouse medulloblastomas. Only those cells expressing MAP/ERK kinase 5 (MEK5) plus ERK5 or MEF2 constructs underwent apoptosis, indicating that overexpression of either is sufficient to induce medulloblastoma cell death. Expression of a dominant-negative MEF2 or small interfering RNA for the ERK5 activator, MEK5, significantly inhibited neurotrophin-3-induced cell death. The dominant-negative MEF2 construct also blocked MEK5/ERK5-induced cell death, supporting a role for MEF2 downstream of ERK5. Co-immunoprecipitation studies revealed direct interaction of phosphorylated ERK5 with MEF2 in response to neurotrophin-3. Our investigation of the mechanism of neurotrophin-3/TrkC-induced apoptosis has identified a novel role for both MEK5/ERK5 and MEF2 in cell death, suggesting that these molecules can be exploited to induce apoptosis in both TrkC-expressing and non-expressing medulloblastoma cells.
Program in Neuroscience, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA.
Lisa-Marie
LM
Sturla
Christopher W
CW
Cowan
Lillian
L
Guenther
Robert C
RC
Castellino
John Y H
JY
Kim
Scott L
SL
Pomeroy
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002528:Cerebellar Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D064326:MEF2 Transcription Factors; D008527:Medulloblastoma / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D048054:Mitogen-Activated Protein Kinase 7 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D020933:Neurotrophin 3 / Q000494:pharmacology; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D020812:Receptor, trkC / Q000096:biosynthesis / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D020933:Neurotrophin 3; D011725:Pyridines; D014157:Transcription Factors; D020812:Receptor, trkC; D048054:Mitogen-Activated Protein Kinase 7; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one