TY - JOUR
T1 - Dual roles for c-Jun N-terminal kinase in developmental and stress responses in cerebellar granule neurons
AU - Coffey, E T
AU - Hongisto, V
AU - Dickens, M
AU - Davis, R J
AU - Courtney, M J
PY - 2000/10/15
Y1 - 2000/10/15
N2 - c-Jun N-terminal kinases (JNKs) typically respond strongly to stress, are implicated in brain development, and are believed to mediate neuronal apoptosis. Surprisingly, however, JNK does not respond characteristically to stress in cultured cerebellar granule (CBG) neurons, a widely exploited CNS model for studies of death and development, despite the regulation of its substrate c-Jun. To understand this anomaly, we characterized JNK regulation in CBG neurons. We find that the specific activity of CBG JNK is elevated considerably above that from neuron-like cell lines (SH-SY5Y, PC12); however, similar elevated activities are found in brain extracts. This activity does not result from cellular stress because the stress-activated protein kinase p38 is not activated. We identify a minor stress-sensitive pool of JNK that translocates with mitogen-activated protein kinase kinase-4 (MKK4) into the nucleus. However, the major pool of total activity is cytoplasmic, residing largely in the neurites, suggesting a non-nuclear role for JNK in neurons. A third JNK pool is colocalized with MKK7 in the nucleus, and specific activities of both increase during neuritogenesis, nuclear JNK activity increasing 10-fold, whereas c-Jun expression and activity decrease. A role for JNK during differentiation is supported by modulation of neuritic architecture after expression of dominant inhibitory regulators of the JNK pathway. Channeling of JNK signaling away from c-Jun during differentiation is consistent with the presence in the nucleus of the JNK/MKK7 scaffold protein JNK-interacting protein, which inhibits JNK-c-Jun interaction. We propose a model in which distinct pools of JNK serve different functions, providing a basis for understanding multifunctional JNK signaling in differentiating neurons.
AB - c-Jun N-terminal kinases (JNKs) typically respond strongly to stress, are implicated in brain development, and are believed to mediate neuronal apoptosis. Surprisingly, however, JNK does not respond characteristically to stress in cultured cerebellar granule (CBG) neurons, a widely exploited CNS model for studies of death and development, despite the regulation of its substrate c-Jun. To understand this anomaly, we characterized JNK regulation in CBG neurons. We find that the specific activity of CBG JNK is elevated considerably above that from neuron-like cell lines (SH-SY5Y, PC12); however, similar elevated activities are found in brain extracts. This activity does not result from cellular stress because the stress-activated protein kinase p38 is not activated. We identify a minor stress-sensitive pool of JNK that translocates with mitogen-activated protein kinase kinase-4 (MKK4) into the nucleus. However, the major pool of total activity is cytoplasmic, residing largely in the neurites, suggesting a non-nuclear role for JNK in neurons. A third JNK pool is colocalized with MKK7 in the nucleus, and specific activities of both increase during neuritogenesis, nuclear JNK activity increasing 10-fold, whereas c-Jun expression and activity decrease. A role for JNK during differentiation is supported by modulation of neuritic architecture after expression of dominant inhibitory regulators of the JNK pathway. Channeling of JNK signaling away from c-Jun during differentiation is consistent with the presence in the nucleus of the JNK/MKK7 scaffold protein JNK-interacting protein, which inhibits JNK-c-Jun interaction. We propose a model in which distinct pools of JNK serve different functions, providing a basis for understanding multifunctional JNK signaling in differentiating neurons.
KW - Animals
KW - Anisomycin/pharmacology
KW - Cell Differentiation/physiology
KW - Cell Nucleus/metabolism
KW - Cells, Cultured
KW - Cerebellum/cytology
KW - Culture Media, Serum-Free/pharmacology
KW - Cytoplasm/metabolism
KW - Excitatory Amino Acid Antagonists/pharmacology
KW - Gene Expression Regulation, Developmental/drug effects
KW - Humans
KW - Isoenzymes/biosynthesis
KW - JNK Mitogen-Activated Protein Kinases
KW - MAP Kinase Kinase 4
KW - MAP Kinase Kinase 7
KW - Mitogen-Activated Protein Kinase Kinases/metabolism
KW - Mitogen-Activated Protein Kinases/genetics
KW - Neurons/cytology
KW - Prosencephalon/cytology
KW - Protein Synthesis Inhibitors/pharmacology
KW - Protein Transport/physiology
KW - RNA, Messenger/metabolism
KW - Rats
KW - Rats, Sprague-Dawley
KW - Signal Transduction/physiology
KW - Stress, Physiological/enzymology
KW - U937 Cells
KW - p38 Mitogen-Activated Protein Kinases
M3 - Article
C2 - 11027220
SN - 1529-2401
VL - 20
SP - 7602
EP - 7613
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 20
ER -