Inhibition of aberrant and constitutive phosphorylation of the high-molecular-mass neurofilament subunit by CEP-1347 (KT7515), an inhibitor of the stress-activated protein kinase signaling pathway.
Previous studies have implicated stress-activated protein kinases (SAPKs) in aberrant phosphorylation of the high-molecular-mass neurofilament subunit (NFH). We now present direct evidence for this involvement using CEP-1347, a specific inhibitor of SAPK activation. Inhibition by this drug of stress-induced phosphorylation of NFH and the middle-molecular-mass neurofilament subunit in the perikaryon of dorsal root ganglion (DRG) neurons paralleled the decrease in levels of activated SAPKs and was essentially complete at 1 microM: CEP-1347. In addition, a role for SAPKs in the constitutive phosphorylation of NFH was demonstrated. Longterm treatment of unstressed DRG neurons with CEP-1347 lowered the steady-state phosphorylation level of NFH in neurites. No such effect was seen in neurons treated with PD 098059, which blocks activation of extracellular signal-regulated kinase 1/2. DRG neurites were shown to contain high basal levels of activated SAPKs. These included a 55-kDa SAPK whose activation was completely abolished at 0.05 microM: CEP-1347 and a 45-kDa SAPK that was not affected by the drug. These results indicate that SAPKs are involved in both stress-induced and constitutive phosphorylation of NFH. The differing responses of SAPKs in neurites and cell bodies to CEP-1347 inhibition further suggest the presence of different signaling pathways in the two neuronal compartments.
O'Ferrall
E K
EK
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Robertson
J
J
Mushynski
W E
WE
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007150:Immunohistochemistry; D007211:Indoles / Q000494:pharmacology*; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D016900:Neurofilament Proteins / Q000378:metabolism*; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects
D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D016900:Neurofilament Proteins; C051774:neurofilament protein H; C106592:3,9-bis((ethylthio)methyl)-K-252a; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases