Role of the NO-activated MAP kinase pathways in carcinogenesis

在本研究项目中，我们取得了以下两个成果。我们发现，在ASK-1缺陷小鼠获得的小鼠胚胎成纤维细胞中，一氧化氮(NO)强烈激活了已知的调节JNK和p38 MAP激酶通路的凋亡信号调节蛋白1(ASK1)，并且NO诱导的p38的早期激活受到损害。这些结果有力地表明，ASK1是NO诱导的MAP激酶通路激活的关键调节因子。最近，我们发现钙内流激活了ASK1。已有研究表明，钙离子内流触发了NO的产生，反过来，NO调节钙稳态，提示NO与钙信号转导有密切关系。为了了解钙信号如何影响钙信号中ASK1-MAP激酶通路的非药物激活，我们研究了钙信号激活ASK1的机制。我们发现，钙/钙调蛋白依赖性蛋白激酶II(CaMKII)-ASK1-MKK3/MKK6-p38构成了一条新的钙信号通路。钙内流激活CaMKII，激活CaMKII，并通过磷酸化激活ASK1。此外，原代神经元和突触体的膜去极化引起的钙内流诱导了p38的强烈激活，而这种激活在ASK-1缺陷小鼠中受到了抑制。因此，ASK1似乎是CaMKII和p38之间钙信号的关键中间体。

In this research project, we have shown the following two results.1. We have shown that nitric oxide (NO) strongly activated apoptosis signal-regulating kinase 1(ASK1), which is known to regulate the JNK and p38 MAP kinase pathways, and that NO-induced early activation of p38 was impaired in mouse embryonic fibroblasts obtained from ASK 1-deficient mice. These results strongly suggest that ASK1 is a pivotal regulator of NO-induced activation of the MAP kinase pathways.2. Recently, we have found that calcium influx activates ASK1. It has been reported that the calcium influx triggers the NO production and that, conversely, NO regulates the calcium homeostasis, suggesting the intimate relationship between NO and calcium signaling. To know how calcium signal affects NO-medicated activation of the ASK1-MAP kinase pathways in calcium signaling, we investigated the activation mechanism of ASK1 by calcium signal. We have shown that a kinase cascade composed of calcium/calmodulin-dependent protein kinase type II (CaMKII)-ASK1-MKK3/MKK6-p38 constituted a novel calcium-signaling pathway. Calcium influx activated CaMKII, and activated CaMKII recruited and activated ASK1 by phosphorylation. Moreover, calcium influx evoked by membrane depolarization in primary neurons and synaptosomes induced strong activation of p38, which was impaired in those derived from ASK 1-deficient mice. Thus, ASK1 appears to be a critical intermediate of calcium signaling between CaMKII and p38.