Epidermal growth factor activates m-calpain (calpain II), at least in part, by extracellular signal-regulated kinase-mediated phosphorylation
Epidermal growth factor activates m-calpain (calpain II), at least in part, by extracellular signal-regulated kinase-mediated phosphorylation
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DOI：
10.1128/mcb.24.6.2499-2512.2004
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发表时间：
2004-03-01
影响因子：
5.3
通讯作者：
Wells, A
中科院分区：
文献类型：
--
作者：
Glading, A;Bodnar, RJ;Wells, A
M-calain是如何在细胞中被激活的，这对研究人员提出了挑战，因为在体外激活需要接近毫米级的钙。此前，我们证明了生长因子激活m-calain需要细胞外信号调节激酶(ERK)；这使得尾巴死粘在一起，并允许生产性运动。我们现在证明ERK在体外和体内都直接磷酸化和激活m-calain。我们在体外和体内鉴定了丝氨酸50是表皮生长因子(EGF)诱导的钙蛋白酶激活所必需的。用丙氨酸代替丝氨酸限制了EGF的激活以及随后的细胞死亡和运动。丝氨酸转化为谷氨酸的构建体在体内表现出结构性活性；雌激素受体融合构建体的表达产生三苯氧胺敏感酶。有趣的是，EGF诱导的m-calain激活发生在没有细胞内钙水平升高的情况下；EGF甚至在细胞内存在钙离子螯合剂和无钙的介质中也会触发calain。这些数据提供了证据，表明m-calain可以通过直接磷酸化的ERK级联被激活，并且这种激活可能在没有细胞内钙流动的情况下发生。
How m-calpain is activated in cells has challenged investigators because in vitro activation requires near-millimolar calcium. Previously, we demonstrated that m-calpain activation by growth factors requires extracellular signal-regulated kinase (ERK); this enables tail deadhesion and allows productive motility. We now show that ERK directly phosphorylates and activates m-calpain both in vitro and in vivo. We identified serine 50 as required for epidermal growth factor (EGF)-induced calpain activation in vitro and in vivo. Replacing the serine with alanine limits activation by EGF and subsequent cell deadhesion and motility. A construct with the serine converted to glutamic acid displays constitutive activity in vivo; expression of an estrogen receptor fusion construct produces a tamoxifen-sensitive enzyme. Interestingly, EGF-induced m-calpain activation occurs in the absence of increased intracellular calcium levels; EGF triggers calpain even in the presence of intracellular calcium chelators and in calcium-free media. These data provide evidence that m-calpain can be activated through the ERK cascade via direct phosphorylation and that this activation may occur in the absence of cytosolic calcium fluxes.