Glycogen synthase kinase-3 is a negative regulator of extracellular signal-regulated kinase.
Glycogen-synthase kinase-3 (GSK-3) and extracellular signal-regulated kinase (ERK) are critical downstream signaling proteins for the PI3-kinase/Akt and Ras/Raf/MEK-1 pathway, respectively, and regulate diverse cellular processes including embryonic development, cell differentiation and apoptosis. Here, we show that inhibition of GSK-3 using GSK-3 inhibitors or RNA interference (RNAi) significantly induced the phosphorylation of ERK1/2 in human colon cancer cell lines HT29 and Caco-2. Pretreatment with the PKCdelta-selective inhibitor rottlerin or transfection with PKCdelta siRNA attenuated the phosphorylation of ERK1/2 induced by the GSK-3 inhibitor SB-216763 and, furthermore, treatment with SB-216763 or transfection with GSK-3alpha and GSK-3beta siRNA increased PKCdelta activity, thus identifying a role for PKCdelta in the induction of ERK1/2 phosphorylation by GSK-3 inhibition. Treatment with SB-216763 increased expression of cyclooxygenase-2 (COX-2) and IL-8, which are downstream targets of ERK1/2 activation; this induction was abolished by MEK/ERK inhibition, suggesting GSK-3 inhibition induced COX-2 and IL-8 through ERK1/2 activation. The transcriptional induction of COX-2 and IL-8 by GSK-3 inhibition was further demonstrated by the increased COX-2 and IL-8 promoter activity after SB-216763 treatment or transfection with GSK-3alpha or GSK-3beta siRNA. Importantly, our findings identify GSK-3, acting through PKCdelta, as a negative regulator of ERK1/2, thus revealing a novel crosstalk mechanism between these critical signaling pathways.
Wang
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Department of Surgery, The University of Texas Medical Branch, Galveston, TX 77555-0536, USA.
Zhou
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Wang
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Evers
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D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D018938:Caco-2 Cells; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D016209:Interleukin-8 / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection
D007211:Indoles; D016209:Interleukin-8; D008301:Maleimides; D034741:RNA, Small Interfering; C417521:SB 216763; D012313:RNA; D008156:Luciferases; D051546:Cyclooxygenase 2; D051745:Protein Kinase C-delta; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D038362:Glycogen Synthase Kinase 3; D012260:Ribonucleases