Inhibition of p38 mitogen-activated protein kinase interferes with cell shape changes and gene expression associated with Schwann cell myelination.
In the present study we demonstrate that p38, a member of the mitogen-activated protein kinase (MAPK) family, is essential for ascorbate- and laminin-induced myelination in Schwann cell-dorsal root ganglion neuron cocultures. The inhibitory effect of the specific p38 blockers, PD 169316 and SB 203580, on ascorbate-induced myelination was exerted during the early stages (1-2 days) of ascorbate treatment. Inhibition of p38 was further shown to prevent the alignment of Schwann cells along axons in laminin-treated cocultures. The addition of laminin to Schwann cell-dorsal root ganglion neuron cocultures stimulated phosphorylation of p38, thereby demonstrating a link between laminin-induced myelination and p38 activation. Similarly, the small heat shock protein, Hsp27, which is phosphorylated by MAPKAPK2, a downstream substrate of p38, was phosphorylated in response to the addition of laminin to the cocultures. The p38 inhibitors did not affect the proliferation or survival of Schwann cells in the cocultures as assessed by BrdU incorporation and total cell counts. However, p38 inhibition interfered with an early stage in myelination, thereby preventing ascorbate-induced increases in the levels of mRNAs encoding MBP, MAG, and P(0) and reducing laminin deposition. These results indicate that activation of p38 by a signaling pathway(s) involving laminin and appropriate integrin receptor(s) is required for the alignment of Schwann cells with axons that precedes myelination.
Fragoso
Gabriela
G
Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
Robertson
Janice
J
Athlan
Eric
E
Tam
Emily
E
Almazan
Guillermina
G
Mushynski
Walter E
WE
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005109:Extracellular Matrix / Q000502:physiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000196:embryology; D015870:Gene Expression / Q000187:drug effects*; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007093:Imidazoles / Q000494:pharmacology; D007797:Laminin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009186:Myelin Sheath / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D002070:Butadienes; D004791:Enzyme Inhibitors; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C486114:Hspb1 protein, rat; D007093:Imidazoles; D007797:Laminin; D009363:Neoplasm Proteins; D009570:Nitriles; C113580:U 0126; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C408604:2-(4-nitrophenyl)-4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazole; D001205:Ascorbic Acid