Ras-independent activation of the Raf/MEK/ERK pathway upon calcium-induced differentiation of keratinocytes
Ras-independent activation of the Raf/MEK/ERK pathway upon calcium-induced differentiation of keratinocytes
复制标题
DOI：
10.1074/jbc.m003716200
复制
发表时间：
2000-12-29
影响因子：
4.8
通讯作者：
Ludwig, S
中科院分区：
文献类型：
--
作者：
Schmidt, M;Goebeler, M;Ludwig, S
MAPK在多种细胞的生长和分化调控中起着至关重要的作用。为了阐明MAPKs在角质形成细胞分化中的作用，分析了细胞外钙刺激下ERK、JNK和p38的激活情况。我们提供的证据表明，钙诱导的角质形成细胞分化与Raf/MEK/ERK通路的快速和瞬时激活有关。用细胞外钙刺激角质形成细胞，在10~15min内可激活Raf同工酶及其下游效应蛋白ERK，但不能增加JNK或p38活性。钙诱导的ERK激活与表皮生长因子诱导的有丝分裂的ERK激活在动力学上是不同的，可以被细胞内钙水平的变化所调节。有趣的是，钙刺激导致RAS活性下调，同时ERK被激活。显性-负性RAS突变体的表达也没有显著地削弱钙诱导的ERK激活，这表明钙介导的ERK激活不需要激活RAS，尽管ERK激活具有暂时性，但钙诱导的细胞周期蛋白依赖的激酶抑制物p21/Cip1和分化标记物Vimucrin的表达对MEK抑制敏感，这表明Raf/MEK/ERK通路在角质形成细胞分化的早期阶段起作用。
MAPKs are crucially involved in the regulation of growth and differentiation of a variety of cells. To elucidate the role of MAPKs in keratinocyte differentiation, activation of ERK, JNK, and p38 in response to stimulation with extracellular calcium was analyzed. We provide evidence that calcium-induced differentiation of keratinocytes is associated with rapid and transient activation of the Raf/MEK/ERK pathway. Stimulation of keratinocytes with extracellular calcium resulted in activation of Raf isozymes and their downstream effector ERK within 10-15 min, but did not increase JNK or p38 activity. Calcium-induced ERK activation differed in kinetics from mitogenic ERK activation by epidermal growth factor and could be modulated by alterations of intracellular calcium levels. Interestingly, calcium stimulation led to down-regulation of Ras activity at the same time that ERK activation was initiated. Expression of a dominant-negative mutant of Ras also did not significantly impair calcium-induced ERK activation, indicating that calcium-mediated ERK activation does not require active Ras, Despite the transient nature of ERK activation, calcium-induced expression of the cyclin-dependent kinase inhibitor p21/Cip1 and the differentiation marker involucrin was sensitive to MEK inhibition, which suggests a role for the Raf/MEK/ERK pathway in early stages of keratinocyte differentiation.