Gas6-mediated survival in NIH3T3 cells activates stress signalling cascade and is independent of Ras
Gas6-mediated survival in NIH3T3 cells activates stress signalling cascade and is independent of Ras
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DOI：
10.1038/sj.onc.1202788
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发表时间：
1999-07-22
期刊：
影响因子：
8
通讯作者：
Schneider, C
中科院分区：
文献类型：
--
作者：
Goruppi, S;Ruaro, E;Schneider, C
Gas6 是维生素 K 依赖性蛋白家族的生长因子膜，优先在静止细胞中表达。 Gas6 被鉴定为 Axl 酪氨酸激酶受体家族的配体。与此一致的是，Gas6 先前被报道可诱导血清饥饿的 NIH3T3 细胞重新进入细胞周期，并防止生长因子完全停用后细胞死亡，这种生存效应与 Gas6 诱导的有丝分裂无关。我们之前已经证明，Gas6 的促有丝分裂和存活效应都是由 Src 和磷脂酰肌醇 3-OH 激酶 (PI3K) 介导的。在这里，我们报道 Ras 对于 Gas6 有丝分裂是必需的，但对于其生存作用来说却是可有可无的。 Gas6 诱导的生存需要 Rho 家族的小 GTPases、Rac 和 Rho 以及下游激酶 Pak 的活性。各自显性失活构建体的过度表达消除了 Gas6 介导的生存功能。向血清饥饿细胞中添加 Gas6 会导致 AKT/PKB 激活以及 Bcl-2 家族成员 Bad 磷酸化。通过催化失活形式的 AKT/PKB 的异位表达，我们证明 AKT/PKB 对于 Gas6 介导的生存功能是必需的。我们进一步证明，Gas6 刺激血清饥饿的 NIH3T3 细胞会导致短暂的 ERK、JNK/SAPK：和 p38 MAPK。激活。阻断 ERK 激活并不影响 Gas6 诱导的存活，表明该途径不参与 Gas6 防止细胞死亡的保护。相反，我们发现与细胞死亡相关的 p38 MAPK 活性的后期组成性增加在 Gas6 处理的 NIH3T3 细胞中下调，因此表明 Gas6 可能通过干扰该途径来促进存活。综上所述，这里的证据提供了参与 Gas6 信号转导的身份元件，更具体地阐明了在不允许细胞增殖的条件下负责 Gas6 诱导的细胞存活的途径。
Gas6 isa growth factor membrane of the vitamin K-dependent family of proteins which is preferentially expressed in quiescent cells. Gas6 was identified as the ligand for Axl tyrosine kinase receptor family. Consistent with this, Gas6 was previously reported to induce cell cycle re-entry of serum-starved NIH3T3 cells and to prevent cell death after complete growth factor withdrawal, the survival effect being uncoupled from Gas6-induced mitogenesis. We have previously demonstrated that both Gas6 mitogenic and survival effects are mediated by Src and the phosphatidylinositol3-OH kinase (PI3K). Here we report that Ras is required for Gas6 mitogenesis but is dispensable for its survival effect. Gas6-induced survival requires the activity of the small GTPases of the Rho family, Rac and Rho, together with the downstream kinase Pak. Overexpression of the respective dominant negative constructs abrogates Gas6-mediated survival functions. Addition of Gas6 to serum starved cells results in the activation of AKT/PKB and in the phosphorylation of the Bcl-2 family member, Bad. By ectopic expression of a catalytically inactive form of AKT/PKB, we demonstrate that AKT/PKB is necessary for Gas6-mediated survival functions. We further show evidence that Gas6 stimulation of serum starved NIH3T3 cells results in a transient ERK, JNK/SAPK: and p38 MAPK. activation. Blocking ERK activation did not influence Gas6-induced survival, suggesting that such pathway is not involved in Gas6 protection from cell death. On the contrary we found that the late constitutive increase of p38 MAPK activity associated with cell death was downregulated in Gas6-treated NIH3T3 cells thus suggesting that Gas6 might promote survival by interfering with this pathway. Taken together the evidence here provided identity elements involved in Gas6 signalling more specifically elucidating the pathway responsible for Gas6-induced cell survival under conditions that do not allow cell proliferation.