Pende M, Fisher T L, Simpson P B, Russell J T, Blenis J, Gallo V
Laboratory of Cellular and Molecular Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Neurosci. 1997 Feb 15;17(4):1291-301. doi: 10.1523/JNEUROSCI.17-04-01291.1997.
To understand how extracellular signals may produce long-term effects in neural cells, we have analyzed the mechanism by which neurotransmitters and growth factors induce phosphorylation of the transcription factor cAMP response element binding protein (CREB) in cortical oligodendrocyte progenitor (OP) cells. Activation of glutamate receptor channels by kainate, as well as stimulation of G-protein-coupled cholinergic receptors by carbachol and tyrosine kinase receptors by basic fibroblast growth factor (bFGF), rapidly leads to mitogen-activated protein kinase (MAPK) phosphorylation and ribosomal S6 kinase (RSK) activation. Kainate and carbachol activation of the MAPK pathway requires extracellular calcium influx and is accompanied by protein kinase C (PKC) induction, with no significant increase in GTP binding to Ras. Conversely, growth factor-stimulated MAPK phosphorylation is independent of extracellular calcium and is accompanied by Ras activation. Both basal and stimulated MAPK activity in OP cells are influenced by cytoplasmic calcium levels, as shown by their sensitivity to the calcium chelator bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid. The kinetics of CREB phosphorylation in response to the various agonists corresponds to that of MAPK activation. Moreover, CREB phosphorylation and MAPK activation are similarly affected by calcium ions. The MEK inhibitor PD 098059, which selectively prevents activation of the MAPK pathway, strongly reduces induction of CREB phosphorylation by kainate, carbachol, bFGF, and the phorbol ester TPA. We propose that in OPs the MAPK/RSK pathway mediates CREB phosphorylation in response to calcium influx, PKC activation, and growth factor stimulation.
为了解细胞外信号如何在神经细胞中产生长期效应，我们分析了神经递质和生长因子诱导皮质少突胶质前体细胞（OP细胞）中转录因子环磷酸腺苷反应元件结合蛋白（CREB）磷酸化的机制。海藻酸盐激活谷氨酸受体通道，以及卡巴胆碱刺激G蛋白偶联胆碱能受体和碱性成纤维细胞生长因子（bFGF）刺激酪氨酸激酶受体，均能迅速导致丝裂原活化蛋白激酶（MAPK）磷酸化和核糖体S6激酶（RSK）激活。海藻酸盐和卡巴胆碱对MAPK途径的激活需要细胞外钙内流，并伴有蛋白激酶C（PKC）的诱导，而与Ras的GTP结合无显著增加。相反，生长因子刺激的MAPK磷酸化不依赖于细胞外钙，并伴有Ras激活。OP细胞中的基础和刺激的MAPK活性均受细胞质钙水平的影响，这一点通过它们对钙螯合剂双（2-氨基苯氧基）乙烷-N，N，N'，N'-四乙酸的敏感性得以体现。CREB磷酸化对各种激动剂的反应动力学与MAPK激活的动力学一致。此外，CREB磷酸化和MAPK激活同样受到钙离子的影响。MEK抑制剂PD 098059能选择性地阻止MAPK途径的激活，强烈降低海藻酸盐、卡巴胆碱、bFGF和佛波酯TPA对CREB磷酸化的诱导。我们提出，在OP细胞中，MAPK/RSK途径介导了对钙内流、PKC激活和生长因子刺激的CREB磷酸化。
