Expression of myelin basic protein in two oligodendroglial cell lines is modulated by apotransferrin through different transcription factors.
We have shown that apotransferrin (aTf) promotes the differentiation of two oligodendroglial cell (OLGc) lines, N19 and N20.1, representing different stages of OLGc maturation. Although in both cell lines aTf promoted myelin basic protein (MBP) expression, an increase in cAMP levels and CREB phosphorylation was observed only in the less mature cells (N19), suggesting that the maturation induced by aTf is achieved probably through different signaling pathways. We transfected both cell lines with the proximal region of the human MBP promoter fused to the lacZ reporter gene. In both transfected cell lines, addition of aTf produced an activation of the promoter. To elucidate the mechanisms involved in this action, Western blot analysis, EMSAs, and RT-PCR were performed for different transcription factors involved in mbp regulation. In the N20.1 line, treatment with aTf increased the expression and the DNA-binding capacity of thyroid hormone (TH) receptors, Sp1, and nuclear factor-kappaB (NFkappaB). For these cells we found that an inductor of NFkappaB (tumor necrosis factor-alpha) promoted MBP messenger synthesis, whereas mithramycin, a specific inibitor of Sp1, and a cAMP analog (db-cAMP) inhibited its transcription. In the N19 cell line, aTf stimulated NF-I and NFkappaB activation, but, aside from aTf, only db-cAMP induced mbp transcription. These data suggest that, depending on the OLGc maturational stage, aTf modulates MBP expression and OLGc differentiation through different signaling pathways and different transcription factors.
Paez
Pablo M
PM
Instituto de Química y Fisicoquímica Biológica (IQUIFIB), UBA-CONICET, Buenos Aires, Argentina.
García
Corina I
CI
Pasquini
Juana M
JM
D001059:Apoproteins / Q000502:physiology*; D015153:Blotting, Western; D002460:Cell Line; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter; D007763:Lac Operon / Q000235:genetics; D004676:Myelin Basic Protein / Q000096:biosynthesis*; D016328:NF-kappa B / Q000235:genetics; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D009836:Oligodendroglia / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000235:genetics; D013778:Tetrazolium Salts; D013844:Thiazoles; D013963:Thyroid Hormones / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology*; D014168:Transferrin / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D001059:Apoproteins; D018076:DNA, Complementary; D004676:Myelin Basic Protein; D016328:NF-kappa B; D009687:Nuclear Proteins; D016329:Sp1 Transcription Factor; D013778:Tetrazolium Salts; D013844:Thiazoles; D013963:Thyroid Hormones; D014157:Transcription Factors; D014168:Transferrin; D014409:Tumor Necrosis Factor-alpha; C028284:apotransferrin; D012313:RNA; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C022616:thiazolyl blue