The MLK family mediates c-Jun N-terminal kinase activation in neuronal apoptosis.
Neuronal apoptotic death induced by nerve growth factor (NGF) deprivation is reported to be in part mediated through a pathway that includes Rac1 and Cdc42, mitogen-activated protein kinase kinases 4 and 7 (MKK4 and -7), c-Jun N-terminal kinases (JNKs), and c-Jun. However, additional components of the pathway remain to be defined. We show here that members of the mixed-lineage kinase (MLK) family (including MLK1, MLK2, MLK3, and dual leucine zipper kinase [DLK]) are expressed in neuronal cells and are likely to act between Rac1/Cdc42 and MKK4 and -7 in death signaling. Overexpression of MLKs effectively induces apoptotic death of cultured neuronal PC12 cells and sympathetic neurons, while expression of dominant-negative forms of MLKs suppresses death evoked by NGF deprivation or expression of activated forms of Rac1 and Cdc42. CEP-1347 (KT7515), which blocks neuronal death caused by NGF deprivation and a variety of additional apoptotic stimuli and which selectively inhibits the activities of MLKs, effectively protects neuronal PC12 cells from death induced by overexpression of MLK family members. In addition, NGF deprivation or UV irradiation leads to an increase in both level and phosphorylation of endogenous DLK. These observations support a role for MLKs in the neuronal death mechanism. With respect to ordering the death pathway, dominant-negative forms of MKK4 and -7 and c-Jun are protective against death induced by MLK overexpression, placing MLKs upstream of these kinases. Additional findings place the MLKs upstream of mitochondrial cytochrome c release and caspase activation.
Xu
Z
Z
Department of Pathology and Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Maroney
A C
AC
Dobrzanski
P
P
Kukekov
N V
NV
Greene
L A
LA
D000818:Animals; D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D015870:Gene Expression; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D016350:Leucine Zippers; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019814:Myristic Acid / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D016716:PC12 Cells; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction; D013564:Sympathetic Nervous System / Q000166:cytology; D014466:Ultraviolet Rays; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
D061945:Caspase Inhibitors; D020169:Caspases; D003574:Cytochrome c Group; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019814:Myristic Acid; D020932:Nerve Growth Factor; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C093290:MAP3K10 protein, human; C109162:MAP3K13 protein, human; C482858:MAP3K5 protein, human; C090757:mitogen-activated protein kinase kinase kinase 12; C482559:MAP2K4 protein, human; C482569:MAP2K7 protein, human