16-kDa prolactin inhibits endothelial cell migration by down-regulating the Ras-Tiam1-Rac1-Pak1 signaling pathway
16-kDa prolactin inhibits endothelial cell migration by down-regulating the Ras-Tiam1-Rac1-Pak1 signaling pathway
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DOI：
10.1158/0008-5472.can-07-0986
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发表时间：
2007-11-15
期刊：
影响因子：
11.2
通讯作者：
Yu-Lee, Li-yuan
中科院分区：
文献类型：
--
作者：
Lee, Sok-Hyong;Kunz, Jeannette;Yu-Lee, Li-yuan
血管生成在促进肿瘤发生和转移中起关键作用。催乳素的16-kDa片段（16 k PRL）是完整的23-kDa催乳素的NH（2）-末端天然分解片段，已被证明具有有效的抗血管生成和抗肿瘤活性。16 k PRL在内皮细胞中的作用机制尚不清楚。在这项研究中，我们发现，16 k PRL减少大鼠主动脉内皮细胞（RAEC）迁移的伤口愈合试验和基质胶管形成试验，表明16 k PRL抑制内皮细胞迁移，血管生成和肿瘤发生的重要活动。我们进一步研究了16 k PRL如何减弱内皮细胞迁移。我们首先表明RAEC迁移是通过Rho GTdR Rac 1介导的，因为Rac 1特异性抑制剂NSC 27366抑制Rac 1或小干扰RNA敲低Rac 1都阻断了RAEC迁移。我们接下来表明，16 k PRL以浓度依赖性方式降低Rac 1的激活。此外，16 k PRL对Rac 1的抑制是通过抑制T淋巴瘤侵袭和转移1（Tiam 1）及其上游激活因子Ras以磷酸肌醇-3-激酶非依赖性方式介导的。16 k PRL还下调Rac 1的下游效应物p21激活激酶1（Pak 1）的磷酸化，并抑制其向迁移细胞前沿的移位。因此，16 k PRL通过阻断内皮细胞中的Ras-Tiam 1-Rac 1-Pak 1信号通路来抑制细胞迁移。
Angiogenesis plays a key role in promoting tumorigenesis and metastasis. The 16-kDa fragment of prolactin (16k PRL) is an NH(2)-terminal natural breakdown fragment of the intact 23-kDa prolactin and has been shown to have potent antiangiogenic and antitumor activities. The mechanism(s) involved in the action of 16k PRL in endothelial cells remains unclear. In this study, we showed that 16k PRL reduced rat aortic endothelial cell (RAEC) migration in a wound-healing assay and in a Matrigel tube formation assay, suggesting that 16k PRL inhibits endothelial cell migration, an important activity involved in angiogenesis and tumorigenesis. We further investigated how 16k PRL attenuates endothelial cell migration. We first showed that RAEC migration is mediated through the Rho GTPase Rac1, as Rac1 inhibition by the Rac1-specific inhibitor NSC27366 or Rac1 knockdown by small interfering RNA both blocked RAEC migration. We next showed that 16k PRL reduced the activation of Rac1 in a concentration-dependent manner. Furthermore, 16k PRL inhibition of Rac1 is mediated through the suppression of T lymphoma invasion and metastasis 1 (Tiam1) and its upstream activator Ras in a phosphoinositide-3-kinase-independent manner. 16k PRL also down-regulated the phosphorylation of the downstream effector of Rac1, p21-activating kinase 1 (Pak1), and inhibited its translocation to the leading edge of migrating cells. Thus, 16k PRL inhibits cell migration by blocking the Ras-Tiam1-Rac1-Pak1 signaling pathway in endothelial cells.