Ras介导的信号转导和转化中的关键事件涉及Ras与其下游效应物靶标的相互作用。尽管大量证据表明Raf-1丝氨酸/苏氨酸激酶是Ras功能的关键效应物,越来越多的证据表明,Ras功能是通过与多种效应子相互作用来介导的,从而触发Raf非依赖性信号通路.除了两种RasGTP酶激活蛋白(GAP;p120-和NF1-GAP),其他候选效应物包括Ras相关Ral蛋白的激活剂(RalGDS和RGL)和磷脂酰肌醇3-激酶。Ras及其效应子之间的相互作用需要完整的Ras效应子结构域,并涉及对活性Ras-GTP的优先识别。令人惊讶的是,这些功能上不同的效应子缺乏显著的序列同源性,并且没有描述共有Ras结合序列。我们现在已经鉴定了在Ras效应子的子集之间共有的共有Ras结合序列。我们还表明,含有来自Raf-1(RKTFLKLA)和NF1-GAP(RRFFLDIA)的该序列的肽可阻断NF1-GAP刺激RasGTP酶活性和Ras介导的丝裂原活化蛋白激酶的活化。总之,共有Ras-GTP结合序列的鉴定为不同效应蛋白与Ras-GTP相互作用的能力建立了结构基础。此外,我们证明含有Ras-GTP结合序列的肽可以阻断Ras功能,为开发抗Ras药物迈出了一步.
A key event in Ras-mediated signal transduction and transformation involves Ras interaction with its downstream effector targets. Although substantial evidence has established that the Raf-1 serine/threonine kinase is a critical effector of Ras function, there is increasing evidence that Ras function is mediated through interaction with multiple effectors to trigger Raf-independent signaling pathways. In addition to the two Ras GTPase activating proteins (GAPs; p120- and NF1-GAP), other candidate effectors include activators of the Ras-related Ral proteins (RalGDS and RGL) and phosphatidylinositol 3-kinase. Interaction between Ras and its effectors requires an intact Ras effector domain and involves preferential recognition of active Ras-GTP. Surprisingly, these functionally diverse effectors lack significant sequence homology and no
consensus Ras binding sequence has been described. We have now identified a
consensus Ras binding sequence shared among a subset of Ras effectors. We have also shown that peptides containing this sequence from Raf-1 (RKTFLKLA) and NF1-GAP (RRFFLDIA) block NF1-GAP stimulation of Ras GTPase activity and Ras-mediated activation of mitogen-activated protein kinases. In summary, the identification of a
consensus Ras-GTP binding sequence establishes a structural basis for the ability of diverse effector proteins to interact with Ras-GTP. Furthermore, our demonstration that peptides that contain Ras-GTP binding sequences can block Ras function provides a step toward the development of anti-Ras agents.