Activated Ras induces cytoplasmic vacuolation and non-apoptotic death in glioblastoma cells via novel effector pathways
Activated Ras induces cytoplasmic vacuolation and non-apoptotic death in glioblastoma cells via novel effector pathways
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DOI：
10.1016/j.cellsig.2006.11.010
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发表时间：
2007-05-01
影响因子：
4.8
通讯作者：
Maltese, William A.
中科院分区：
文献类型：
--
作者：
Kaul, Apama;Overmeyer, Jean H.;Maltese, William A.
活化的H-Ras表达诱导人类胶质母细胞瘤细胞和其他特定肿瘤细胞系的一种独特形式的非凋亡细胞死亡。这种死亡形式的主要细胞病理学特征是大量相朗朗、lamp1阳性的细胞质空泡的积累。在这项研究中，我们试图确定细胞质空泡化的诱导是否a)取决于Ras法酰化，b)是H-Ras特异性的，以及c)是通过已知的主要Ras效应通路的信号传导介导的。我们发现活化的H-Ras的不同寻常的作用取决于法尼化和GTPase的膜结合。H-Ras（G12V）和K-Ras4B（G12V）都能刺激空泡形成，但活化的Cdc42和RhoA则不能。Ras效应域的氨基酸替换，已知会选择性地破坏其与Raf激酶、i类磷脂酰亚苷3-激酶（PI3K）或Ral核苷酸交换因子的相互作用，最初指出Raf可能是细胞空泡化的介质。然而，MEK抑制剂PD98059不能阻断液泡的诱导，并且组成活性的Raf-Caax不能模仿Ras（G12V）的作用。将正常PTEN和H-Ras（G12V）一起引入U251胶质母细胞瘤细胞，可降低pi3k依赖性Akt的激活，但对空泡形成没有影响。最后，H-Ras（G12V）与Ra1A的显性阴性形式共表达不抑制空泡形成。综上所述，这些观察结果表明，Ras激活非常规的、可能是独特的效应途径，诱导胶质母细胞瘤细胞的细胞质空泡化。对相关信号通路的鉴定可能会揭示特定的分子靶点，这些靶点可以被操纵来激活这种类型癌症中的非凋亡细胞死亡。(c) 2006爱思唯尔公司版权所有。
Expression of activated H-Ras induces a unique form of non-apoptotic cell death in human glioblastoma cells and other specific tumor cell lines. The major cytopathological features of this form of death are the accumulation of large phase-lucent, LAMP1-positive, cytoplasmic vacuoles. In this study we sought to determine if induction of cytoplasmic vacuolation a) depends on Ras farnesylation, b) is specific to H-Ras, and c) is mediated by signaling through the major known Ras effector pathways. We find that the unusual effects of activated H-Ras depend on farnesylation and membrane association of the GTPase. Both H-Ras(G12V) and K-Ras4B(G12V) stimulate vacuolation, but activated forms of Cdc42 and RhoA do not. Amino acid substitutions in the Ras effector domain, which are known to selectively impair its interactions with Raf kinase, class-I phosphatidylinositide 3-kinase (PI3K), or Ral nucleotide exchange factors, initially pointed to Raf as a possible mediator of cell vacuolation. However, the MEK inhibitor, PD98059, did not block the induction of vacuoles, and constitutively active Raf-Caax did not mimic the effects of Ras(G12V). Introduction of normal PTEN together with H-Ras(G12V) into U251 glioblastoma cells reduced the PI3K-dependent activation of Akt, but had no effect on vacuolation. Finally, co-expression of H-Ras(G12V) with a dominant-negative form of Ra1A did not suppress vacuolation. Taken together, the observations indicate that Ras activates non-conventional and perhaps unique effector pathways to induce cytoplasmic vacuolation in glioblastoma cells. Identification of the relevant signaling pathways may uncover specific molecular targets that can be manipulated to activate non-apoptotic cell death in this type of cancer. (c) 2006 Elsevier Inc. All rights reserved.