Inhibition of Ras extracellular-signal-regulated kinase (ERK) mediated signaling promotes ciliary neurotrophic factor (CNTF) expression in Schwann cells.
Ciliary neurotrophic factor (CNTF) can prevent injury-induced motor neuron death. However, it is also evident that expression of CNTF in Schwann cells is suppressed during nerve regeneration. In this report, we have addressed the mechanism underlying the down-regulation of CNTF expression in injured nerves using a mouse Schwann cell line IMS32 and mouse sciatic nerve. In IMS32 cells, activation of the Ras extracellular-signal-regulated kinase (ERK) pathway by adenoviral vector-mediated expression of dominant active MEK1 did not alter a basal level of CNTF expression, whereas inhibition of the Ras-ERK pathway by using adenoviral vectors resulted in a marked increase in CNTF expression. This inverse relation between before and after axotomy was also observed in mouse sciatic nerve. In the axotomized sciatic nerve, the phosphorylated ERK was markedly increased; in contrast, the expression of CNTF was markedly decreased. These findings suggest that an inactive state of ERK is crucial for the CNTF expression in Schwann cells, and that activation of ERK following nerve injury critically influences the expression of CNTF. This might well explain why CNTF is highly expressed in quiescent Schwann cells in the peripheral nervous system, and also why CNTF is not abundant in axotomized nerves or cultured Schwann cells in which the proliferation signal is obviously active.
Abe
K
K
Departments of Anatomy and Psychiatry and Neurology, Asahikawa Medical College, Asahikawa, Japan.
Namikawa
K
K
Honma
M
M
Iwata
T
T
Matsuoka
I
I
Watabe
K
K
Kiyama
H
H
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D020934:Ciliary Neurotrophic Factor / Q000096:biosynthesis* / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D005813:Genes, Synthetic; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D048369:MAP Kinase Kinase 1; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009416:Nerve Regeneration; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012583:Schwann Cells / Q000378:metabolism*; D012584:Sciatic Nerve / Q000293:injuries; D015398:Signal Transduction / Q000502:physiology*
D020934:Ciliary Neurotrophic Factor; D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)