RalA requirement for v-Src- and v-Ras-induced tumorigenicity and overproduction of urokinase-type plasminogen activator: involvement of metalloproteases
RalA requirement for v-Src- and v-Ras-induced tumorigenicity and overproduction of urokinase-type plasminogen activator: involvement of metalloproteases
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DOI：
10.1038/sj.onc.1202850
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发表时间：
1999-08-19
期刊：
影响因子：
8
通讯作者：
Foster, DA
中科院分区：
文献类型：
--
作者：
Aguirre-Ghiso, JA;Frankel, P;Foster, DA
尿激酶型纤溶酶原激活物（uPA）和金属蛋白酶（MMPs）的过度产生与致瘤性以及人类和实验性肿瘤的侵袭性和转移性表型密切相关。我们以前证明，uPA在特纳细胞中的过度生产是由磷脂酶D（PLD）和蛋白激酶C依赖性机制介导的。v-Src和v-Ras的致癌刺激导致PLD的激活，而PLD的激活依赖于单体GTP酶RaLA。因此，我们研究了RaLA是否在响应致癌信号而观察到的uPA和MNP过度产生中起作用。在v-Src和v-Ras转化的细胞中，显性负性RalA突变体（S28 N）的表达阻断uPA的过度产生。v-Src和v-Ras也诱导MMP-2和MMP-9活性的上调，但只有v-Src的诱导作用与蛋白质印迹分析检测到的MMP蛋白水平相关。显性负性RalA突变体阻断了v-Src诱导的MMP-2和MMP-9的过度产生，但不阻断v-Ras诱导的MMP-2和MMP-9活性的增加。并且，与RalA/PLD途径在有丝分裂和肿瘤发展中的作用一致，显性负性RaLA突变体完全阻断了在同基因小鼠中皮下注射的v-Src-和v-Ras-转化的NIH 3 T3细胞的肿瘤形成。这里提供的数据暗示RalA和PLD作为转化细胞的肿瘤形成和蛋白酶产生的信号传导介质。
Overproduction of urokinase-type plasminogen activator (uPA) and metalloproteases (MMPs) is strongly correlated with tumorigenicity and with invasive and metastatic phenotypes of human and experimental tumors. We demonstrated previously that overproduction of uPA in turner cells is mediated by a phospholipase D (PLD)and protein kinase C-dependent mechanism. The oncogenic stimulus of v-Src and v-Ras results in the activation of PLD, which is dependent upon the monomeric GTPase RalA, We have therefore investigated whether RaLA plays a role in uPA and MNP overproduction that is observed in response to oncogenic signals, We report here that NIH3T3 cells transformed by both v-Src and v-Ras, constitutively overproduce uPA and that expression of a dominant negative RalA mutant (S28N) blocks overproduction of uPA in both the v-Src-and v-Ras-transformed cells. v-Src and v-Ras also induced an upregulation of the activity of MMP-2 and MMP-9 as detected by zymograms, however only the v-Src induction correlated with MMP protein levels detected by Western blot analysis, The dominant negative RalA mutant blocked increased MMP-2 and 9 overproduction induced by v-Src, but not the increased activity of MMP-2 and 9 induced by v-Ras. And, consistent with a role for the RalA/PLD pathway in mitogenesis and tumor development, the dominant negative RaLA mutant completely blocked tumor formation by v-Src- and v-Ras-transformed NIH3T3 cells injected subcutaneously in syngeneic mice, The data presented here implicate RalA and PLD as signaling mediators for tumor formation and protease production by transformed cells.