Activation of the phosphatidylinositol 3-kinase/Akt signaling pathway by retinoic acid is required for neural differentiation of SH-SY5Y human neuroblastoma cells.
Retinoic acid (RA) induces neural differentiation of SH-SY5Y neuroblastoma cells. We show that the mRNA levels of the differentiation-inhibiting basic helix-loop-helix transcription factors ID1, ID2, and ID3 are down-regulated during RA-induced differentiation of SH-SY5Y cells. The levels of ID proteins decreased in parallel to the observed transcriptional repression. The expression of other basic helix-loop-helix genes changed during RA-induced differentiation: expression of neuroblast-specific ASCL1 (HASH-1) gene was promptly reduced after RA treatment, whereas expression of differentiation-promoting genes NEUROD6 (NEX-1, HATH-2) and NEUROD1 was increased. Treatments with 12-O-tetradecanoylphorbol-13-acetate, another inducer of neuroblastoma cell differentiation, also resulted in coordinated down-regulation of ID gene expression, underscoring the role of ID genes in differentiation. Down-regulation of ID gene expression by RA involves a complex mechanism because full transcriptional repression required newly synthesized proteins and signaling by phosphatidylinositol 3-kinase (PI3K). RA treatment activates the PI3K/Akt signaling pathway, resulting in increased PI3K activity in extracts from RA-treated cells and a rapid increase in phosphorylation of Akt in Ser-473. Inhibition of PI3K by LY294002 impaired RA-induced differentiation, as assessed by morphological and biochemical criteria. We propose that RA, by activating the PI3K/Akt signaling pathway, plays an important role in the regulation of neuronal cell survival.
López-Carballo
Gracia
G
Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas, Spain.
Moreno
Lucrecia
L
Masiá
Susana
S
Pérez
Paloma
P
Barettino
Domingo
D
D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D002454:Cell Differentiation / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D014157:Transcription Factors; D014212:Tretinoin; C494918:AKT1 protein, human