Rac1 inhibits myogenic differentiation by preventing the complete withdrawal of myoblasts from the cell cycle
Rac1 inhibits myogenic differentiation by preventing the complete withdrawal of myoblasts from the cell cycle
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DOI：
10.1074/jbc.m103195200
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发表时间：
2001-10-05
影响因子：
4.8
通讯作者：
Bengal, E
中科院分区：
文献类型：
--
作者：
Heller, H;Gredinger, E;Bengal, E
小GTdR蛋白Rac 1参与了广泛的生物学过程，但其在细胞分化中的作用大多是未知的。在这里，我们表明，Rac 1活性是高增殖成肌细胞和分化过程中下降。为了分析Rac 1在肌肉分化中的参与，在肌肉细胞中表达了不同形式的蛋白质。Rac 1的组成性激活形式（Rac 1 Q61 L）抑制MyoD促进肌肉分化的活性，而Rac 1的显性负性形式（Rac 1 T17 N）诱导MyoD促进肌肉分化的活性。Rac 1 T17 N的表达对在促有丝分裂条件下生长的成肌细胞施加肌源性分化。在研究Rac 1是否影响成肌细胞从细胞周期中退出时，我们分析了细胞周期蛋白D1和p21（WAF 1）的表达以及视网膜母细胞瘤蛋白的磷酸化状态。根据这些标志物和溴脱氧尿苷掺入，C2成肌细胞表达Rac 1 T17 N退出细胞周期早于对照C2细胞。表达Rac 1 Q61 L的成肌细胞不会永久退出细胞周期。通过使用MAPK激酶抑制剂U 0126和PD 098059获得了可能参与Rac 1介导的成肌细胞增殖的丝裂原活化蛋白激酶（MAPK）途径的指示。这些抑制剂阻止C2-Rac 1 Q61 L细胞周期。总之，我们的研究结果表明，Rac 1激活干扰成肌细胞退出细胞周期通过或与MAPK途径。
The small GTPase protein Rac1 is involved in a wide range of biological processes, yet its role in cell differentiation is mostly unknown. Here we show that Rac1 activity is high in proliferating myoblasts and decreases during the differentiation process. To analyze the involvement of Rac1 in muscle differentiation, different forms of the protein were expressed in muscle cells. A constitutively activated form of Rac1 (Rac1Q61L) inhibited the activity of MyoD in promoting muscle differentiation, whereas a dominant negative form of Rac1 (Rac1T17N) induced the activity of MyoD in promoting muscle differentiation. Expression of Rac1T17N imposed myogenic differentiation on myoblasts growing under mitogenic conditions. In inquiring whether Rac1 affected the withdrawal of myoblasts from the cell cycle, we analyzed the expression of cyclin D1 and p21(WAF1) and the phosphorylation state of the retinoblastoma protein. According to these markers and bromodeoxyuridine incorporation, C2 myoblasts expressing Rac1T17N exited the cell cycle earlier than control C2 cells. Myoblasts expressing Rac1Q61L did not permanently withdraw from the cell cycle. An indication of the possible involvement of the mitogen-activated protein kinase (MAPK) pathway in Rac1-mediated myoblast proliferation was obtained by the use of MAPK kinase inhibitors U0126 and PD098059. These inhibitors arrested C2-Rac1Q61L cell cycling. Taken together, our results show that Rac1 activation interferes with myoblast exit from the cell cycle via or in concert with the MAPK pathway.