Mitogen-activated protein kinase pathway mediates N-(4-hydroxyphenyl)retinamide-induced neuronal differentiation in the ARPE-19 human retinal pigment epithelial cell line.
We have shown previously that N-(4-hydroxyphenyl)retinamide (4HPR, fenretinide), a retinoic acid derivative, induces neuronal differentiation in cultured human retinal pigment epithelial (RPE) cells [Chen et al., J. Neurochem., 84 (2003), 972]. We asked the question whether the mitogen-activated protein kinase (MAPK) pathway is involved in the regulation of the 4HPR-induced neuronal differentiation of RPE (ARPE-19) cells. When we treated ARPE-19 cells with 4HPR, c-Raf and MEK1/2 kinase were activated resulting in activation of the downstream effector ERK1/2 and of SAPK/JNK. By blocking the upstream kinase MEK1/2 with specific inhibitor U0126 we abrogated the 4HPR-induced phosphorylation of ERK1/2 and SAPK/JNK, indicating that the neuronal differentiation occurs through a positive cross-talk between the ERK and the SAPK/JNK pathways. Both U0126 and the suppression of ERK1/2 expression with small interfering RNA effectively blocked the 4HPR-induced neuronal differentiation of RPE cells and the expression of calretinin. The activated ERK1/2 then induced a sequential activation of p90RSK, and increase in phosphorylation of transcription factors c-fos and c-jun leading to transcriptional activation of AP-1. Taken together, our results clearly demonstrate that c-Raf/MEK1/2 signaling cascade involving ERK1/2 plays a central role in mediating the 4HPR-induced neuronal differentiation and calretinin expression in the human ARPE-19 retinal pigment epithelial cell line.
Samuel
William
W
Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, Bethesda, Maryland, USA. samuelw@nei.nih.gov
Kutty
R Krishnan
RK
Sekhar
Sonia
S
Vijayasarathy
Camasamudram
C
Wiggert
Barbara
B
Redmond
T Michael
TM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D064032:Calbindin 2; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D017313:Fenretinide / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000166:cytology; D034741:RNA, Small Interfering / Q000494:pharmacology; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D000970:Antineoplastic Agents; C576764:CALB2 protein, human; D064032:Calbindin 2; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D064030:S100 Calcium Binding Protein G; D017313:Fenretinide; D020928:Mitogen-Activated Protein Kinases