Lack of hippocalcin causes impairment in Ras/extracellular signal-regulated kinase cascade via a Raf-mediated activation process
Lack of hippocalcin causes impairment in Ras/extracellular signal-regulated kinase cascade via a Raf-mediated activation process
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DOI：
10.1002/jnr.21180
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发表时间：
2007-03-01
影响因子：
4.2
通讯作者：
Takamatsu, Ken
中科院分区：
文献类型：
--
作者：
Noguchi, Hajime;Kobayashi, Masaaki;Takamatsu, Ken
Hippocalin(HPCA)是神经元钙感受器蛋白家族的一员，在海马神经元中高表达。HPCA基因缺陷(HPCA(-/-))小鼠表现出cAMP反应元件结合蛋白(CREB)激活缺陷，与空间和联想记忆受损有关。在这里，我们研究了HPCA在导致CREB激活的细胞外信号调节激酶(ERK)级联中的参与，因为广泛的ERK级联抑制剂PD98059的应用已经导致HPCA-1海马区CREB激活的相似水平。N-甲基-D-天冬氨酸(NMDA)和KCl诱导的ERK在HPCA(-/-)脑片中的磷酸化显著减弱，而Forsklin和12-O-十四酰佛波醇-13-乙酸酯(TPA)刺激后，野生型和HPCA(-/-)脑片中ERK的磷酸化水平无明显差异。在体外重组实验系统中，重组HPCA既不影响以重组MEK-1为底物的Raf-1蛋白激酶的活性，也不影响以ERK2为底物的MEK-1的活性。NMDA型和KCl型大鼠海马脑片对RAS的激活无明显差异，而HPCA(-/-)脑片中Raf-1的磷酸化水平显著降低。这些结果表明，HPCA在RAS激活RAF的过程中起着重要作用。(C)2007年Wiley-Liss，Inc.
Hippocalcin (Hpca) is a member of the neuronal calcium sensor protein family and is highly expressed in hippocampal neurons. Hpca-deficient (Hpca(-/-)) mice display a defect in cAMP response element-binding protein (CREB) activation associated with impaired spatial and associative memory. Here we examine the involvement of Hpca in the extracellular signal-regulated kinase (ERK) cascade leading to CREB activation, because application of PD98059, a broad ERK cascade inhibitor, has resulted in similar levels of CREB activation in Hpca-1hippocampus. N-methyl-D-aspartate (NMDA)- and KCl-induced phosphorylation of ERK was significantly attenuated in Hpca(-/-) hippocampal slices, as was ionomycin-induced phosphorylation of ERK, whereas forskolin and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulation yielded indistinguishable levels of ERK phosphorylation in both wild-type and Hpca(-/-) slices. In an in vitro reconstitution assay system, recombinant Hpca affected neither Raf-1 protein kinase activity with recombinant MEK-1 as a substrate nor MEK-1 kinase activity with ERK2 as a substrate. Activation of Ras by NMDA and KCl stimulation of hippocampal slices showed no obvious changes between the two genotypes; however, phosphorylation of Raf-1 was significantly lower in Hpca(-/-) slices. These results suggest that Hpca plays an important role in the activation of Raf conducted by Ras. (c) 2007 Wiley-Liss,Inc.